Prosthetic legs in 2026: knees, feet, sockets, Medicare K-levels, cost and what 660 FDA reports show

Stop and check today

Wearing a prosthetic leg now? Check these first. Choosing one, or trying to understand what Medicare will pay? Start at the short answer below.

• Your knee buckled, went soft, locked, beeped or vibrated without a reason. Sit down, use the manual lock if your knee has one, and call your prosthetist before you walk on it again. Össur's Rheo Knee manual says: "In case of power failure, malfunction, or warnings it is recommended to engage the mechanical lock."
• Your microprocessor knee is low on charge. The C-Leg 4 user manual warns of "Falling due to unexpected behaviour of the prosthesis because of changed damping behaviour" when the charge is too low. Check the charge before you go out.
• You charge the knee while wearing it. The same manual says: "For safety reasons, take the product off before charging the battery."
• A mechanical knee has play, clicks, or a screw or bolt that is loose or missing. Stop using it and take it to the prosthetist; do not tighten joint bolts yourself.
• The pin no longer clicks home in the socket lock, the liner is torn, or the leg feels like it could slip off. A lock that stops holding the pin can let the leg come off mid-step.
• You see a crack in the foot, the pylon or an adapter, or hear a new crack or squeak. Stop and get it checked.

These checks match the problems behind most of the FDA reports we read, which are counted later in this guide. None of them needs tools. Anything that changes how the knee or socket behaves is a job for your prosthetist, not a home repair.

The short answer

A prosthetic leg is a set of parts built around you: a socket that fits your residual limb, a liner and a way of holding the leg on (suspension), a knee if the amputation is above the knee, a pylon and adapters, and a foot. The knee and the foot are where most of the choices are, and Medicare decides which of them it will pay for by your functional level, the "K-level", from 0 to 4.

Knees range from simple mechanical hinges to hydraulic and pneumatic knees, microprocessor knees that change their resistance as you walk, and powered knees with a motor. Feet range from a basic SACH foot to carbon energy-storing feet and microprocessor ankles. Under Medicare's lower limb rule, microprocessor knees and energy-storing and microprocessor feet are covered for level 3 users and above, and since 1 September 2024 also for level 2 users who meet extra written criteria; powered knees and ankles have stricter rules, set out below.

Prices are the hard part. The makers' pages we read for the C-Leg 4, Kenevo, Rheo Knee, Power Knee and Pro-Flex XC publish no price, and neither does any Medicare document we read. Medicare sets your share instead: after the Part B deductible, you pay 20 percent of the Medicare-approved amount. Repairs, replacement and sockets have their own rules, set out below.

Mobility Atlas earns a fee or margin when you order through us; this guide uses only Medicare's coverage rules, the makers' own product pages and manuals, FDA reports and recall records, and our own catalog, read in October 2026. Choosing the knee, foot, socket and alignment, and setting the K-level, belongs to your treating practitioner and your prosthetist. This guide explains the options and what to ask, and stops there.

The parts of a prosthetic leg

Below-knee legs have no knee, so the socket, suspension and foot carry all the choices. Above-knee and hip-level legs add a knee, and often a rotator or other components. Medicare's rule says the type of knee and the type of foot will be decided "by the treating practitioner and/or the prosthetist based upon the functional needs of the beneficiary."

Prosthetic knees: the main kinds

Medicare's rule says the basic prosthesis includes "a single axis, constant friction knee", and it groups the rest by how they control the swing and the stance. In plain words:

Mechanical knees have no battery and nothing to charge, and some are rated for fresh-water use (check the rating of yours); they need you to control the knee with your hip and timing. Microprocessor knees aim to hold you if you stumble and to let you walk down stairs and slopes step over step, but they need daily or near-daily charging and regular servicing by the maker. Medicare's rule says as much: for a level 2 user, the person must be "able to make use of a product that requires daily charging" and to "understand and respond to error alerts and alarms."

Four microprocessor and powered knees, from the makers' documents

We read the product pages (Ottobock's US pages; Össur's English international pages, as its US page redirected) and the instructions for use of the C-Leg 4, Rheo Knee and Power Knee in October 2026; for the Kenevo we read the US product page only. These are the makers' own figures; none of the pages shows a price.

The Kenevo page is inconsistent about water: its list for users says "IP54 Rating" and its specification table says "IP22 (protected against dripping water)". Ask your prosthetist which applies to your knee before it meets rain. Össur adds a note to its K-level figures: "They do not reflect regional reimbursement policies or relate to coverage of specific devices." A maker's K-level is the use the knee is designed for, not a promise that Medicare will pay.

The Kenevo is built for users who walk slowly and not far: its page limits it to "patients who walk with speeds of up to 1.9 mph and up to ½ mile outside the house per day," and lists a wheelchair function, supported sitting down and standing up, and a manual lock. The C-Leg 4 page lists "Stumble Recovery Plus active at all times" and a manual lock set by a tapping pattern. The Rheo Knee has a manual lock "at the press of a button." The Power Knee uses a motor and says its powered lift "enables supported step-over-step stair ascent."

Powered knees and powered ankles

A powered knee or ankle has a motor that adds energy, not just resistance. Medicare treats the two very differently. The powered knee addition, L5859, is covered only for a level 3 user who already has a swing-and-stance microprocessor knee, has "a documented comorbidity of the spine and/or sound limb affecting hip extension and/or quadriceps function" that limits walking with the microprocessor knee alone, and can handle daily charging and alarms. A powered ankle, L5969, is not covered at all: Medicare's rule says "Claims for L5969 will be denied as not reasonable and necessary."

Power has its own risks. Össur's Power Knee manual says: "In case of an unexpected power loss the device will stop moving and may not return to full extension." Its battery is rated for 4 to 20 hours, depending on activity, and takes about 5 hours to charge when fully depleted. Ask how the knee behaves at low charge, what the warnings sound and feel like, and what you should do when they start.

Prosthetic feet: from SACH to microprocessor ankles

Medicare's rule says "Basic lower extremity prostheses include a SACH foot" (a solid ankle with a cushioned heel), and ties every other foot to your functional level.

A level 2 user can get one of the level 3 feet only if they also meet the level 2 criteria for a fluid, pneumatic or microprocessor knee and, the rule says, "a higher-level (i.e., functional level 3) foot is required for the safe and proper use of the prescribed knee system." In practice that rule is for users whose leg has a prosthetic knee.

Feet have weight and impact categories. Össur's Pro-Flex XC manual, for example, sets stiffness categories by weight and impact level and warns: "Do not exceed weight limit. Risk of device failure." The same foot is tested to two million load cycles under ISO 10328, which the manual says "may correspond to 2-3 years of use." It is rated waterproof, including salt and chlorinated water, but the manual says sand and dirt are tolerated only occasionally.

Sockets, liners and suspension

The socket matters more than any part you can buy off a shelf, and it is the part that changes most. Medicare's rule says it allows up to two test (diagnostic) sockets for a prosthesis, more only with documentation, and "No more than two of the same socket inserts" at the same time. A socket replacement is covered with "adequate documentation of functional and/or physiological need", and the rule names changes in the residual limb, changes in functional need, and irreparable damage or wear from weight or a very active user.

Suspension is how the leg stays on. Common kinds are a pin on the end of the liner that clicks into a lock in the socket, a seal or sleeve with a one-way expulsion valve that holds the socket by suction, a lanyard, and an elevated vacuum system with a pump. Ottobock's recall file describes one of its valves as "a threadless one-way valve" used "to evacuate air from the prosthetic socket." Each kind has a part that wears: the lock plates and pin, the seal, the valve. Ask your prosthetist how to tell when yours is wearing, and keep a spare liner if you can.

A prosthetic donning sleeve (L7600) "will be denied as noncovered," Medicare's policy article says. Liners, socks and inserts have their own codes and limits; ask the prosthetist what your plan allows each year.

Medicare K-levels in plain words

How do Medicare K-levels decide which prosthetic knee and foot are covered? Mobility Atlas read Medicare's coverage rule for lower limb prostheses, LCD L33787, and its policy article in October 2026. A practitioner and a prosthetist rate your potential from level 0 to level 4, written K0 to K4. Level 0 means a prosthesis would not help, and Medicare denies it. Level 1 is walking at home on level ground at a fixed pace; it covers a SACH or single axis foot and simpler mechanical knees. Level 2 adds curbs, a few stairs and uneven ground, and opens flexible-keel and multiaxial feet. Level 3 is walking at varied speeds in the community; it is the usual level for hydraulic, pneumatic and microprocessor knees and for energy storing and microprocessor feet. Level 4 is high-impact use such as running. Since 1 September 2024 (LCD revision R11), a level 2 user can get a microprocessor knee or a level 3 foot when extra written criteria are met.

The policy article says "Not all traits listed for K levels must be realized by the patient" to be assigned a level, and the rule says the rating is based on "potential functional ability", not only what you do today. It also says "bilateral amputees often cannot be strictly bound by functional level classifications."

How your K-level is decided and recorded

The rule says the level is based on "the reasonable expectations of the treating practitioner and prosthetist," looking at your past history, including any earlier prosthesis, your current condition, the state of the residual limb, other medical problems, and your desire to walk. To be covered at all, the rule says you must be expected to "reach or maintain a defined functional state within a reasonable period of time" and be "motivated to ambulate."

Paperwork matters. The policy article says: "The simple entry of a K-level modifier in those records is not sufficient." The records must describe your history and current condition, and explain any difference between what you do now and what you are expected to do. If your level seems wrong, ask the practitioner and the prosthetist what they wrote and why, and what would change it. Your level can change as you recover or as your health changes.

When Medicare covers a microprocessor knee

For a level 3 or level 4 user, a microprocessor knee (L5856, L5857 or L5858) falls within the rule, with documentation of functional need. For a level 2 user, the rule, revised from 1 September 2024 (revision R11), says it covers fluid, pneumatic and microprocessor knees "under limited circumstances," when all of these are true:

1. You have had a clinical evaluation to set your functional level.
2. Your records explain why this knee, including how it will improve your functional health outcomes (the rule says examples include "fall reduction, injury prevention, lower energy expenditure") and help with your activities of daily living.
3. Lower-level knees without fluid, pneumatic or microprocessor control have been considered and ruled out.

For a microprocessor knee at level 2, four more conditions apply: the knee must be indicated for level 2; it must have technology that detects a trip or stumble and stabilises the knee (the rule's example is "stumble recovery"); you must be able to manage daily charging; and you must be able to understand and respond to error alerts and alarms. The Kenevo and Rheo Knee pages describe their knees as made for lower activity levels, and the C-Leg 4 lists K2 among its levels; whether one suits you is for the prosthetist and practitioner to decide.

Prosthetic leg cost: what a Medicare user pays

What does a prosthetic leg cost a Medicare user? Mobility Atlas read Medicare's prosthetic devices page and its lower limb rules in October 2026, and none of them gives a dollar price; nor does any maker page we read. The pages for the C-Leg 4, Kenevo, Rheo Knee, Power Knee and Pro-Flex XC publish no price, and a fitted leg is billed by the prosthetist as a set of HCPCS codes: the C-Leg 4 page alone suggests six. What Medicare sets is your share. Part B covers prosthetic devices that a doctor or other provider orders, and after the Part B deductible you pay 20 percent of the Medicare-approved amount, from a supplier that participates in Medicare. The approved amount includes the evaluation, the fitting, and repairs for normal wear within 90 days of delivery. Later repairs are covered when they are needed to make the leg work. Ask the prosthetist for a written estimate of the approved amount and of your 20 percent before the fitting.

Medicare's page adds that "Some states may require prior authorization for certain types of lower-limb prosthetics before Medicare will pay," and that what you owe depends on other insurance, what the provider charges, whether they accept assignment, and where you get the item. It also warns: "Your doctor may recommend services that Medicare does not cover or offers too frequently." Ask which parts of your leg are covered and which are not before you agree to them.

Medicare's policy article says these are "included in the reimbursement for a prosthesis and, therefore, are not separately billable": the evaluation of the residual limb and gait, the fitting, the base parts and labour, repairs for normal wear within 90 days of delivery, and adjustments made at fitting and for 90 days after delivery when your limb or abilities have not changed.

Repairs, adjustments and replacement

Medicare's policy article says there are three different things. A repair is "a restoration of the prosthesis to correct problems due to wear or damage." An adjustment is a change because your condition changed or to improve function. Routine servicing is different again: "Routine periodic servicing, such as testing, cleaning, and checking of the prosthesis is noncovered." But maintenance that the maker requires and that "must be performed by the prosthetist is covered as a repair."

• Adjustments needed because of wear or a change in your condition are covered under the original order "for the life of the prosthesis," the article says.
• Repairs are covered when needed to make the leg work. If the repair would cost more than a whole new prosthesis, Medicare pays nothing for the excess.
• A replacement leg or major part (foot, ankle, knee, socket) needs a new order and a documented reason: a change in your body or function, wear that cannot be repaired, or a repair that would cost more than 60 percent of a replacement.
• A leg that is lost or damaged beyond repair may be replaced without a new order if the original prescription still meets your needs.
• Artificial limbs have no fixed useful-lifetime limit: the article says payment can be made "without regard to continuous use or useful lifetime restrictions" when the practitioner finds the replacement reasonable and necessary.

Keep every service report and repair invoice. They are the evidence for the 60 percent rule and for a replacement when the time comes.

Service intervals and how long parts last

Ottobock's C-Leg 4 manual ties the interval to activity: for users "with up to 1,800 steps per day, the expected maintenance interval is 3 years," and for more active users 2 years. It says "Regular service inspections (maintenance) are mandatory in the interest of your own safety and in order to maintain operating reliability and protect the warranty." The knee signals when maintenance is due. Medicare covers maker-required maintenance done by the prosthetist as a repair, so ask the prosthetist to book it, and ask for a loaner knee while yours is away.

Batteries, charging and power loss

Every microprocessor knee runs on a rechargeable battery, and the manuals are blunt about what happens when it runs out. Össur's Rheo Knee manual says: "A case of unexpected power failure or battery depletion during use will cause the device to stop functioning normally and may subject the patient to the risk of falling." At 5 percent charge it warns with sound or vibration; at 0 percent the knee "stops operating, gives shutdown audio feedback and shuts down."

• Charge every day, whatever the battery life says. The Rheo manual says: "Charge the battery daily for optimal performance."
• Take the leg off to charge it. The C-Leg 4 manual warns of "Falling due to walking and getting caught on a connected battery charger," and says the knee is non-functional while charging.
• Expect less battery in the cold and as the battery ages. The C-Leg 4 manual says operating time "may be reduced at low ambient temperatures or due to ageing of the battery."
• Learn each warning: the beeps, vibrations and lights, and what each one means. Medicare's level 2 criteria assume you can respond to them.
• Do not open the knee or touch the battery. The C-Leg 4 manual says "The battery may only be handled by authorised, qualified Ottobock personnel (no replacement by the user)."

Water, weather and strong magnets

Water ratings differ a lot between knees, and between the electronics and the metal parts. The C-Leg 4 is rated IP68 for occasional fresh water to 3 m for 1 hour, but the manual says "the mechanical components may corrode" and the knee "should not come into contact with salt water, chlorinated water or other solutions (such as soap or shower gel, and body and wound fluids)." The Rheo Knee and the Power Knee are "Weatherproof": rain is fine, "no submersion is allowed", and no salt or chlorinated water. The Kenevo page gives two different ratings, IP54 and IP22.

Feet differ too. The Pro-Flex XC is rated "Waterproof" and its manual says it can be "submerged in up to 3-meter-deep water for a maximum of 1 hour." If you swim or shower standing, ask the prosthetist about a separate water leg or waterproof parts, rather than taking a knee where its manual says it should not go.

Magnets and scanners matter as well. The Kenevo page says strong magnetic fields such as MRI "can cause irreparable damage to microprocessor knees" and that they "should be removed before entering a room or area where strong magnetic fields exist." The Rheo manual names CT and MRI scanners among the places the knee should not be used. Tell hospital staff before any scan.

Stairs, ramps and slopes

Stairs and slopes are where knees are tested hardest. The C-Leg 4 page lists "Supported descent on ramps and stairs"; the Rheo Knee manual says "Always use the handrail when walking down ramps and stairs." Medicare's K-level examples use stairs as a yardstick: 1-2 stairs for level 2, 3-7 consecutive stairs for level 3, repetitive stair climbing for level 4.

• Use the handrail on stairs and ramps, even if the knee supports step-over-step descent.
• Practise new stair and ramp skills with a physical therapist before you rely on them at home.
• Light the stairs, keep them clear, and put a rail on both sides if you can.
• If a stairlift is part of your home, practise the turn and first step off it with the therapist; the stairlift guide covers the lift itself.
• Wear the shoes your leg was aligned with. A change in heel height changes the alignment.

Osseointegration and hip-level legs

Some users have a bone-anchored implant instead of a socket: a titanium implant anchored in the bone, with an abutment the leg attaches to, so no socket is needed. Our catalog lists the Integrum OPRA Implant System, which the maker says is FDA approved in the US for above-knee use, and OTN Implants' BADAL X. Surgery and candidacy are for a surgical team to decide, and the implant itself is outside the scope of this guide and its FDA reports.

The knee and foot still matter. The Rheo Knee and Power Knee pages list "Compatible with Osseointegration" as "Yes", and the Kenevo page lists osseointegration among its applications along with bilateral above-knee and hip disarticulation fittings. For hip-level amputations, Medicare covers a pneumatic or hydraulic polycentric hip joint (L5961) for level 3 users and above. Ask your prosthetist which parts are approved together; some knees and hips are tested only with certain partners.

A wheelchair and a prosthesis together

Many people with a leg amputation use both a prosthesis and a wheelchair. Medicare's own level 1 description includes a person who "requires the use of a wheelchair for most activities outside of their residence," and level 2 may need a wheelchair "for distances that are beyond the perimeters of the yard/driveway." The Kenevo page lists a "Wheelchair function" that "facilitates maneuvering in a wheelchair," and a donning function for putting the leg on while seated.

A prosthesis does not have to replace the chair. Ask the prosthetist and the therapist how the leg sits in the chair, how you transfer with it on and off, and where the knee goes when you push. For the chair side, see the Mobility Atlas guide to lightweight and travel wheelchairs.

Canes, crutches and other help while you learn

Many users rely on a walking aid at some point: while the limb heals, while learning a new knee, or on bad days. The K-level descriptions say "with or without an assistive device," so a cane or crutches do not lower your level by themselves. The Mobility Atlas guides to walking canes and crutches cover fit and safety. For people who cannot use a prosthesis to stand or walk, the exoskeleton guide covers powered braces, and the bionic arm guide covers upper-limb prostheses.

Other ways to pay

Medicare is only one route. Medicare Advantage plans, Medicaid, the VA, workers' compensation and private insurers each set their own rules, supplier networks and prior authorization steps, and they differ by state. Confirm with your plan before the fitting which knee, foot and socket codes it covers, what you will pay, and how repairs and replacements are handled. Outside the US, public health systems and insurers have their own lists and rules; ask your clinic.

Questions for your prosthetist

• What K-level have you recorded for me, and what did you write to support it?
• Which knee and foot do you recommend, and which lower-level options did you rule out, and why?
• Is this knee indicated for my level, and does it have stumble recovery and a manual lock?
• How long does the battery last for someone like me, and what do its warnings sound and feel like?
• What is the Medicare-approved amount for this leg, and what is my 20 percent?
• How often does the knee need maker service, and will I get a loaner while it is away?
• What water, salt, chlorine and sand can each part take?
• How will I know when the socket, liner or lock is wearing, and how often should I come back?

If you are looking for a specific knee, foot or liner, ask us to find it through the enquiry form; we will tell you who supplies it and what the documents say. The prescription stays with your prosthetist.

What 660 FDA reports show: the big picture

What goes wrong with prosthetic legs, according to FDA reports? Mobility Atlas had two independent AI coders read 714 FDA reports filed under seven lower-limb prosthesis product codes, up to October 2026; 660 of them are about a prosthetic leg. Most concern knees. In the 295 reports about microprocessor knees, the usual story is a knee that buckled, lost its resistance or did not hold the user, and a fall: 264 describe a fall and 224 an injury, while the maker found no fault, or an outside cause, in 133. In the 239 reports about mechanical knees, the usual story is a part of the joint, very often a bolt, that came loose or broke; the maker confirmed a fault in 190. Sockets, liners and locks (54 reports) and non-powered feet (43) follow. Across all 660, 409 describe a fall and 353 an injury. These are reports, not rates, and two makers filed most of them.

The two big groups tell opposite stories. Microprocessor knee reports are mostly falls, and the maker usually found nothing wrong or could not check. Mechanical knee reports are mostly repairs, without a fall, of a part the maker found broken or loose. Neither story says which kind of knee is safer: the counts depend on who files and why, as the sections below explain.

Which part the reports name

Each report was coded for the part it says failed first, as alleged, even when the maker later found no fault.

The pattern is plain: joint and bolt reports are high in confirmed faults and low in falls, while give-way reports with no part named are high in falls and low in confirmed faults. Many of those falls left nothing a maker could find on the bench, which is why the knee's warnings, charge and service history matter so much.

Microprocessor knees: falls when the knee gives way

295 reports concern microprocessor or powered knees, 243 of them naming Ottobock (C-Leg, Genium, Kenevo and others) and 45 Össur (Rheo Knee, Symbionic Leg, Power Knee). 264 describe a fall and 224 an injury. In 103 the knee is said to have buckled, collapsed, locked or given way with no part named. In 67 the report names the hydraulic unit, most often saying resistance or hydraulic support was lost: one Rheo Knee report says "the resistance dropped out causing the pt to fall," and a Kenevo report says "knee buckled, device showed no resistance" (the maker found no failure and said the device "operated within specification"). A C-Leg report says "the joint bent when descending stairs, resulting in a fall."

In 52 the report alleges no failure at all, most often (48) a fall while the user wore the knee, and in 43 it names the electronics, a mode or an alarm, and in 22 the battery or charger. The maker found no fault or named an outside cause in 133, could not evaluate or drew no conclusion in 136, and confirmed a fault in 26. By a word search of the event descriptions, 80 of the 295 mention a fracture, 42 stairs, 29 the hip and 27 the head.

Many reports end the same way: the device "is currently not available for evaluation," and a supplemental report will follow. Some describe a knee that misbehaved more than once. One Genium report says the knee, which was "locking up," "inadvertently failed to release into swing phase resulting in falls," three of them; the maker's evaluation "showed no relevant error which may have caused or contributed to the occurred event." If your knee gives way even once without a clear reason, that is the moment to call the prosthetist, not after a second time.

Batteries, electronics, modes and apps

The microprocessor knee reports that name a cause often name something the user can see or hear first. A Kenevo report says the knee "beeps once and then malfunctions (no damping)." A C-Leg report says the "knee was not charged for 3 days then buckled causing patient to fall"; the maker later found "air in the hydraulics because of the patient not meeting the service interval" and named that as the cause. A message quoted in one Kenevo report says the user's knee from time to time "goes all limp." By a word search, 26 of the 295 microprocessor knee reports mention a beep, vibration or alarm, and 21 a battery.

Modes are another theme. A Genium X3 report describes a user who "forgot knee was in cycling mode" after an exercise bike and fell. In a C-Leg report the user changed the mode by app and the knee buckled; the phone then showed "mode change incomplete." A 2026 report on another maker's knee says the knee had gone into power-saving mode "as designed" and the user "did not perceive the device's audible and vibratory notification prior to power-off."

• Know which mode the knee is in before you stand, especially after cycling or sitting a long time.
• Treat a beep, vibration or warning light as a reason to stop, sit and lock the knee, not as background noise.
• Charge daily, and send the knee in when it stops holding a charge.
• If the knee has a manual lock, practise using it with the prosthetist so you can do it without thinking.

Mechanical knees: one knee family's loose bolts

239 reports concern knees without a battery: mechanical, polycentric, hydraulic or pneumatic. 191 name the knee joint, its axle, links or bolts, and 159 describe a part that came loose, every one of them an Ottobock EBS knee joint (modular, modular polycentric, or its knee- and hip-disarticulation versions). Most are short repair notes. A 2015 report says the "bolt fell out of the side," and the maker's evaluation found "the adhesive did not harden correctly." Many later reports end with the same sentence: "no fall or injury occurred due to this failure, but it could have led to patient injury."

The maker confirmed a fault in 190 of the 239 mechanical knee reports, and 180 of the joint reports carry a confirmed fault. Only 66 describe a fall and 46 an injury. 21 report texts are exact copies of another report's text, all of them short EBS repair notes. Separately, an FDA recall from 2016 covers 40 Modular Polycentric EBS knee joints (3R60) "serviced between 27 April 2015 and 17 November 2015 due to a service error where the wrong Loctite was used during repair," the recall says.

Most of the other mechanical knee reports describe a fall (38 of 48). 21 allege a problem without naming a part: most say the knee buckled, locked or would not bend, and a few describe only a fall. One Total Knee report says "the knee locked as the patient was stepping on defective flooring"; the maker, which did not get the knee back, said the user "fell likely due to broken floor board at home." A polycentric knee should feel the same every day. New play, a click, a squeak or a bolt head that stands proud is a reason to take it in.

Feet, pyramids and adapters

43 reports concern non-powered feet and ankles. 23 name the pyramid adapter or connector, 19 of them a part that broke, and 8 the keel or foot plate. 27 describe a fall and 25 an injury. Many come from one foot model's reports, in which the end-user, a report says, was walking "when the pyramid adapter snapped in half," or "heard a crack" and found the foot disconnected from the pylon. Another report says a foot "broke just below the pyramid causing the patient to fall," with a broken hip.

13 more reports concern a pylon, adapter or other component with no knee or foot as the subject; 11 name the pylon, tube or adapter, and 10 describe a fall. A 1999 report says "the pylon tube in her above knee prosthesis broke." These parts are small and easy to forget. Look at them when the cover is off, and ask the prosthetist to check the adapters and torque at every visit.

Sockets, liners and locks

54 reports concern sockets, liners, locks and valves, 43 of them naming Össur. 45 name the socket, liner, lock or valve, and in 34 the part let go: a lock that released the pin, a seal that lost suction, a liner that separated. 33 describe a fall and 38 an injury. An Iceross liner report says the user "lost the vacuum and came out of the socket." A 2001 report says a pin "disengaged with the locking mechanism," the foot section came away, and the user fell and fractured a fibula.

19 socket reports arrived in 2023, the year Össur recalled Icelock ratchet locks whose pin and lock "can wear down faster than expected." Several reports from that time are short: "the lock is no longer holding the pin securely," one says, and another "mechanism worn out after 6 months use." A 2024 maker narrative says "all components in the lock mechanism are now hardened during manufacturing."

• Listen for the click as the pin engages, every time you put the leg on.
• Check the liner for tears and the seal for nicks when you take it off.
• If the leg pistons more than usual or the lock needs extra effort, ask the prosthetist to check the lock plates and pin.

Powered feet, batteries and smoke

Six reports concern powered or microprocessor feet. Two describe a battery for a powered ankle that overheated or caught fire while charging; one says it "over heated during charging and began to smoke," and the other found the charger set to the wrong charging mode. A Power Knee report describes a user who "observed smoke emitting from the battery pack" while driving. An FDA recall from 2012 covers the same powered ankle's battery, which "may over-heat during charging and smoke," the recall says.

Charge prosthetic batteries with the maker's charger, on its correct setting, where you can see them, and never leave a battery that smells, swells or gets hot on charge.

Falls, fractures and stairs in the reports

409 of the 660 reports describe a fall and 353 an injury; 329 describe both. By a word search of the event descriptions, 109 mention a fracture, 57 stairs, 41 the hip, 35 the head and 19 a ramp, slope, incline or hill. 105 of the 109 fracture mentions are in reports that describe a fall.

The fractures named include hips, femurs, wrists, shoulders and the sound leg's knee. Several reports describe a user with a bone-anchored implant whose femur broke in a fall; one says "I have a osseointegrated patient who has fallen while using his c-leg and fractured his femur." Falls also happen with nothing wrong: 80 reports allege no failure, and 70 of them describe a fall. If you fall, get checked even if you feel fine, and tell the prosthetist about every fall.

When the report points to a setting, water or charging

In 94 of the 660 reports, the report says the user or someone else caused the problem, or the maker concluded so: a knee left in the wrong mode, an alignment or setting by the clinic, water or sand, overload, a part from another maker, charging in the wrong way, or missed service. By a word search, 22 reports mention water, rain, a shower or swimming, and 45 service or maintenance.

In one report a clinician suspected that slippers with "a lower heel height" than the shoes the leg was aligned with may have played a part, and "wants the knee checked out to be sure"; the maker drew no conclusion. Others describe a knee used long after its service date. These are not excuses; they are the parts of the system a user and a prosthetist control, and they are worth checking together.

The death reports, read with care

Three reports were filed as deaths, all about microprocessor knees. In a 2018 report, a reimbursement facility said a user fell down a staircase and died, "probably due to a hydraulic defect on the knee joint." The maker said "no clear statements about possible malfunctions can be made," and that it can be assumed "the loss of oil mostly arose as a result of the described event"; the report adds that an older, not-serviced knee was in use. In a 2025 report, a user fell on the basement stairs wearing a loaner knee and later died; the supplier "could not detect any defects in the knee joint" and wrote: "we have no information as to whether this happened as a result of the accident." The maker said it saw "no causal connection between the reported fall of the user and his regrettably subsequently reported passing." In another 2025 report, a user fell after stepping off a stair lift and broke a hip; the clinician "suspects" a change of footwear and "wants the knee checked out to be sure," and later wrote: "so, while the fall did not directly cause her death, it was the first domino in a series of events that ultimately contributed to it." That is the clinician's view; the maker made no statement on the cause.

A death report records what the reporter believed; the FDA says reports carry a "lack of verification that the device caused the reported event." In two of these reports the maker or supplier said it could not link the fall to the death, or that no clear statement about the knee could be made; in the third the maker drew no conclusion. What the reports do show is how serious a fall can be, which is why handrails, charge and an early call about a knee that gives way matter.

What the makers found

Across the 660 reports, the maker found or confirmed a fault in 247, found no fault or named an outside cause in 184, and did not evaluate or drew no conclusion in 229. The split follows the kind of device: confirmed faults in 190 of the 239 mechanical knee reports, against 26 of the 295 microprocessor knee reports. Outside causes the makers named include the fall itself, a mode left on, alignment, missed service, water, and parts from other makers.

Who files: two makers and their filing years

Ottobock is named as the maker in 484 of the 660 reports and Össur in 139; the remaining 37 name another maker or none, and a few of those are Ottobock or Össur products filed without the maker's name. That reflects who files, not which legs fail more. Makers are mandatory reporters, and large makers with service centres and complaint systems file on the complaints that reach them. The FDA's own page says the data "is not intended to be used either to evaluate rates of adverse events" or "to compare adverse event occurrence rates across devices."

The years show the same thing. Reports were few until the 2010s, then rose to 68 in 2016 and 100 in 2017, of which Ottobock filed 56 and 90; in 2020 there were 84, 78 of them Ottobock. The 2020 peak looks like a filing batch: 19 EBS repair notes arrived on a single day. About half of the 2016 and 2017 peak is EBS repair notes too: 85 EBS reports in those two years, received on 60 different days, 68 of them describing a joint part, usually a bolt, that came loose. Separately, Ottobock recalled 40 3R60 knees serviced in 2015 with the wrong Loctite; the reports themselves do not tie the peak to that recall. Neither peak is a measure of how often legs fail. Since 2014, 2023 is the only year Össur filed more reports than Ottobock (25 against 21), with the Icelock lock reports.

What these reports cannot tell you

The reports are a record of what people and companies chose to tell the FDA, not a count of every problem with a prosthetic leg. Many problems are fixed at the clinic and never reported. The FDA says the incidence, prevalence or cause of an event "cannot be determined from this reporting system alone due to under-reporting of events, inaccuracies in reports, lack of verification that the device caused the reported event, and lack of information about frequency of device use."

So the counts say nothing about which knee, foot or maker is safer. They show which problems reach the FDA, in which words, and how often a fall comes with them. The product codes matter too: of the 660 leg reports, 467 were filed under ISY (knee joints), 81 under ISH (ankle and foot components), 81 under ISW (knee-shank-ankle-foot assemblies), 28 under ISS (sockets) and 3 under ISP (valves); none of the leg reports was filed under KFX or ISL.

The recall file

We read every FDA recall record under the seven product codes: 45 records, of which 42 concern leg prostheses (two are skin-marker tapes for imaging from a vascular device maker, filed under KFX and one an implanted hip stem under ISL). They run from 2003 to 2024. They cover microprocessor knees, mechanical knees, feet, adapters, socket locks and valves.

• Össur Rheo Knee, 2024: "firmware issues" with "the potential for unintended warnings and device shutdown which could result in patient falls," the recall says.
• Össur Power Knee, 2023: batteries that may need replacing to avoid "a failure to turn on the device, or an unexpected shutdown"; and in 2022, a recall because the "Battery may dislodge from the Power Knee."
• Össur Icelock ratchet locks, 2023: a pin and lock that "can wear down faster than expected," which can lead to "loss of suspension," the recall says.
• Ottobock Kenevo, 2017: a pylon clamp design issue in which, after about 1.45 million cycles, with the clamp tightened to the labeled torque and a user weighing at most 125kg, "it may be remote that the pylon breaks," the recall says, adding that "There have been no failures or complaints reported" for that failure mode; it covered 75 knees, and 4 of the =ST version, in the United States and Canada.
• Ottobock Triton Smart Ankle app, 2015: a software issue could make the foot move "unnoticed by the user, who could fall."
• Ottobock Modular Polycentric EBS knees (3R60), 2016: 40 units serviced in 2015 with "the wrong Loctite," the recall says.
• Össur Total Knee models, 2006: "faulty pins based in the axis of the knee," the recall says; and in 2015 Ottobock's Pheon knee, whose "locking function may fail under certain conditions," its recall says.

Ask your prosthetist to check every part of your leg, knee, foot, lock, valve and adapters, against the recall database, and to tell you whether any correction was done.

When to report a prosthetic leg problem to the FDA

Anyone can report a problem with a medical device to the FDA through MedWatch: online, or on the paper form by mail or fax (download it from the FDA, or call 800-332-1088 to request one). Report a knee that gave way, a lock that released, a part that broke, a battery that smoked, and any fall with injury. Tell your prosthetist and the maker too; makers are "mandatory reporters" to the FDA.

Keep the parts, write down what happened, where and how, take photos of labels and serial numbers, and ask the prosthetist for the service report. A clear account helps the maker find the cause, and helps the next user.

How Mobility Atlas read 714 FDA reports

The FDA collects reports about medical devices in a database called MAUDE. Makers, importers and user facilities are "mandatory reporters"; patients, families and clinicians can report voluntarily. On 18 October 2026 we read, through openFDA, every report with a description filed under seven product codes for external leg prosthesis parts: ISY (knee joints), ISH (ankle and foot components), ISW (knee-shank-ankle-foot assemblies), ISS (thigh sockets), ISP (valves), ISL (hip joints) and KFX (complete leg assemblies), at any date: 714 reports, the oldest leg report from 1993 and the newest received on 28 September 2026.

Before reading a single report, we wrote a codebook: the kind of device (microprocessor or powered knee, knee without a battery, powered foot, non-powered foot, socket or liner, hip joint, other component, kind unclear, another device), the part the report says failed first, how it failed (broke, came loose, gave way, stopped working, wore out), flags for injury, a fall and a cause outside the device, and what the maker found. The codebook was fingerprinted with a time stamp before coding began.

Two independent coders then read every report separately, without seeing each other's answers. The coders were AI language models working separately; the method page says exactly how. They agreed on the kind of device in 99.6 percent of reports (kappa 0.994; kappa is a standard measure of agreement beyond chance), on injury in 99.4 percent and on a fall in 99.3 percent, on how it failed in 85.4 percent (kappa 0.808), and on the part in 72.8 percent (kappa 0.674). The part was the hardest call, because reports often name a symptom (the knee gave way) and the maker later names a different part. We settled all 287 reports where the coders differed on any field under eleven written rules, decided from the full report text, and a consistency pass then changed the codes of 197 more so that like reports were coded alike.

54 reports in the pool turned out to be about other devices, mostly implants such as artificial hips, knees and heart valves, and orthoses and braces filed under these codes; they were set aside. The 660 reports about a prosthetic leg are this guide's data. Where we give a count from a word search, it runs over the description of the event, not over the maker's later follow-up notes. 23 report texts are exact copies of another report in the set and are counted as filed. Quotes from reports are shown in sentence case; the FDA publishes most of them in upper case.

Three composite scenarios

These are composite scenarios, not individual customers. Each one combines facts and ranges already given in this guide to show how the decision plays out.

Scenario one: an above-knee user rated level 2 walks at home and to the corner shop. The prosthetist and practitioner consider a microprocessor knee under the September 2024 rule, record why lower-level knees were ruled out, and confirm the user can charge it daily and respond to its alarms. Under Part B the user pays 20 percent of the approved amount after the deductible, and asks for the figure in writing first.

Scenario two: a microprocessor knee beeps and goes soft as the user stands from a chair after a long sit. The user sits back down, engages the manual lock, checks the charge and the mode, and calls the prosthetist the same day instead of walking on it.

Scenario three: a below-knee user notices the pin no longer clicks home in the socket lock. The prosthetist finds worn lock plates, replaces them as a covered repair, and checks the lock against the recall database.

Mistakes to avoid (from the reports and the manuals)

• Walking on a knee that has already given way once without a clear reason (reports: many describe a knee that buckled or gave way before a fall).
• Standing up with the knee still in cycling or another special mode (reports: a Genium X3 report describes a fall after the user forgot the cycling mode).
• Letting the battery run low (C-Leg 4 and Rheo Knee manuals), or charging the knee while wearing it (C-Leg 4 manual).
• Missing the maker's service interval (C-Leg 4 manual; in one report the maker named a missed service as the cause of a fall).
• Changing to shoes with a different heel height from the ones the leg was aligned with (two reports raise footwear as a possible factor).
• Ignoring a loose bolt, new play or a click in a mechanical knee (reports: 159 describe a loose part in EBS knees).
• Using a socket lock that no longer clicks home (reports and the 2023 Icelock recall).

Your plan: 10 minutes, today, this week

In 10 minutes: check the charge, the mode and the manual lock on your knee; listen for the click of the socket lock; look for cracks in the foot and adapters.

Today: write down the model and serial number of your knee, foot, lock and liner, and the date of the last service.

This week: ask the prosthetist when the next maker service is due, what your K-level is and what was written to support it, and whether any part is under recall.

Sources and documents

Reports: every FDA MAUDE device report with a description under product codes ISY, ISH, ISW, ISS, ISP, ISL and KFX, at any date, read through openFDA on 18 October 2026; 660 of them concern a prosthetic leg, the newest received on 28 September 2026. Recalls: all 45 FDA recall records for those codes, downloaded through openFDA, of which 42 concern leg prostheses. Funding: Medicare's coverage rule for lower limb prostheses, LCD L33787, its policy article A52496, and Medicare's prosthetic devices page. Products: Ottobock's US product pages for the C-Leg 4 and Kenevo, Össur's English international pages for the Rheo Knee, Power Knee and Pro-Flex XC, the instructions for use of the C-Leg 4, Rheo Knee, Power Knee and Pro-Flex XC, and the Mobility Atlas catalog. Every source is linked in the list at the end of this page.

Related guides on Mobility Atlas: Walking canes; Crutches; Lightweight and travel wheelchairs; Exoskeletons; Bionic arms.

Method in brief: we coded the 714 reports in the pool using a codebook written and fingerprinted before coding, with two independent coders (agreement on the kind of device 99.6 percent, kappa 0.994; on the part 72.8 percent, kappa 0.674), settled the 287 reports where they differed under written rules, changed 197 more in a consistency pass, set aside 54 reports about other devices, and counted the results by script. The two coders were AI language models working separately, each without access to the other's answers. The codebook, the rules, the method and the coded table are on the data and method page under CC BY 4.0.

Prices checked October 2026: none of the maker pages or Medicare documents we read publishes a price for a knee, foot or complete leg, and the few component prices in our catalog are not confirmed on the makers' public pages, so this guide gives Medicare's cost-sharing rules instead. Documents checked October 2026: FDA reports and recall records, the Medicare coverage rule, policy article and page, and the makers' pages and manuals.

Has a knee, foot or socket let you down, or served you well for years? Send us a note through the enquiry form with the model and what happened; we use readers' notes when we update the guide.