Part 5 of 5 in Your First Year with a Prosthesis, a series with Bethany Nelson, PT.
Prosthesis types, socket fit, policy & access, and a reference glossary.
Some parts of prosthetic rehabilitation don’t fit the month-by-month arc of the first year, but they matter throughout. This article is the reference piece for the series: how different prosthesis types shape training, why socket fit is the single biggest predictor of success, why your physical therapist’s role extends beyond exercises, where the policy landscape is shifting, and a glossary of the vocabulary you’ll encounter.
Training differs by prosthesis type
What you practice depends heavily on what kind of prosthesis you’re using, which depends on the level of your amputation.
Below-knee (transtibial)
A below-knee prosthesis consists of a prosthetic foot and a pylon — a straight shaft that stands in for the tibia, the lower leg bone. Because the natural knee joint remains intact, training is often faster and more straightforward.
The prosthesis replaces the ankle, and the ankle, Bethany points out, is “probably the most important joint for balance.” Keeping your own knee provides substantial stability that the ankle alone can’t compensate for. Some below-knee amputees can walk without an assistive device almost from day one — “it might not be pretty” — though therapy improves gait quality significantly over time.
Above-knee (transfemoral)
Above-knee amputations introduce a prosthetic knee joint, and that changes everything. “Because a knee can buckle,” Bethany says, “and when knees buckle, you end up on the floor until you learn how to deal with those buckles.” Learning to control that knee is the central challenge of above-knee training.
There are two broad categories of prosthetic knees.
Mechanical knees function essentially as hinges. Walking with one demands strong muscle engagement — particularly through the glutes. When the prosthetic leg swings forward and the heel strikes the ground, the user has to actively push the heel down into the ground, which contracts the gluteal muscles and locks the knee before weight is loaded onto it. If that chain breaks, the knee folds. The learning curve is steeper, and the fall risk during early training is real.
Microprocessor-controlled knees use electronic sensors and hydraulics to provide built-in stability that responds to movement in real time. The knee resists unexpected bending on its own, which dramatically reduces the muscle work and cognitive load needed to walk safely.
Bethany’s position is unambiguous:
“Those microprocessor-controlled knees are absolutely the best. That’s the best kind of knee for any above-the-knee amputee, in my opinion.”
Access depends on insurance justification, but she advocates for them whenever the case can be made.
Myoelectric (upper extremity)
Myoelectric prostheses are currently used primarily for arms and hands. Small electrodes are placed over specific muscles — often the pectoralis (chest) muscles for high-level amputations — and the user learns to trigger movements in the prosthetic hand by activating those muscles. Contract the right muscle and the hand opens or closes.
Research into lower-limb myoelectric systems is ongoing, though practical use is still emerging. Bethany hasn’t yet encountered lower-limb myoelectric prostheses in her own 25+ years of clinical practice; her understanding is that PTs working with the military rehabilitation population are among the first seeing them.
Socket fit is the #1 predictor of success
Across everything Bethany has said about prosthetic rehab, one principle sits at the top: socket fit is the single most important factor in long-term success.
“The socket has to fit snug as a glove, and it has to grab onto your skeletal bony contours as best as it can — to feel like it’s hanging from your skeleton rather than hanging from your soft tissues.”
That distinction matters more than it might sound. A well-fitting socket feels like part of the skeletal frame — secure, integrated, trustworthy. A poorly fitting socket feels like a separate object dangling off soft tissue, and it drives almost every frustration covered elsewhere in this series: the socket pain, the skin issues, the gait compromises, the erosion of confidence.
This is why so much of the first year is devoted to managing sock ply, requesting socket modifications, and eventually reaching the definitive socket — the stable, long-term fit. It’s not just comfort. It’s the foundation everything else rests on.
Your PT as advocate
A less-visible part of the rehabilitation journey is the partnership between your physical therapist and your prosthetist. Bethany’s role goes beyond delivering exercises:
“If sock ply isn’t doing it, I call the prosthetist and say, ‘Hey, we’re having some gapping in the socket here, or it’s too tight here, and this is why this patient is not progressing.’ Because I know what I know about prosthetics, I can talk to a prosthetist about the alignment things and fit issues that I’m seeing, and advocate for the client that they have to have a good fit in their socket, and this socket needs to be remade. I’m very much an advocate for my clients.”
That matters for patients in two practical ways.
Your PT sees things in your prosthesis that you may not. Gait asymmetries, alignment issues, unusual wear patterns, subtle pressure marks — these are early signals that the prosthesis isn’t quite right, and your PT is often the first to spot them. The PT’s clinical eye is one of the reasons regular outpatient therapy pays off long after you’re walking confidently.
You can ask your PT to advocate for you. If something doesn’t feel right, and adding or removing socks hasn’t solved it, your PT can (and should) communicate directly with your prosthetist about what they’re observing. You don’t have to translate the problem yourself.
A good PT–prosthetist partnership, with you at the centre, is one of the under-appreciated predictors of a successful long-term outcome.
Policy, insurance, and access
Prosthetic care is partly a clinical question and partly a policy question — and the policy landscape is shifting.
Insurance cadence for new prostheses. In the United States, insurance will generally cover a new prosthesis every five to seven years, though specific policies vary. New sockets, independent of the full prosthesis, can be justified any time there’s a meaningful change in limb circumference — weight gain, weight loss, or continuing shrinkage. The prosthetist is the authoritative source for what’s coverable and when.
The So That Everybody Can Move Act. Recently passed by Congress, this legislation aims to expand insurance coverage for items that weren’t historically covered — most notably shower legs, sport-specific prostheses, and running blades. It reflects a growing recognition that amputees deserve the tools to participate fully in everyday life, not just to walk.
Scholarship programs. For items that still fall outside insurance coverage, several prosthesis manufacturers run scholarship programs with application processes. Elevate is one that Bethany specifically calls out as offering scholarships for running blades; other manufacturers have similar programs. Your prosthetist or PT can often point you toward current programs.
Items you may have to ask for. Bethany notes that some useful options — like shower legs — are not always offered proactively. It’s worth asking your prosthetist explicitly about any of the extras covered elsewhere in this series (shower legs, rotators, running blades). The answer may be “of course,” or it may open a conversation about alternatives.
Glossary
Terms you’ll encounter throughout this series and in conversations with your care team:
- Donning / Doffing — Putting on (donning) and taking off (doffing) the prosthesis. A foundational skill that takes more practice than most new users expect.
- Residual limb — The part of the limb that remains after amputation.
- Liner — A cushioning sleeve, typically silicone or gel, worn directly against the residual limb inside the socket.
- Socket — The part of the prosthesis that the residual limb fits into. Fit, alignment, and volume management of the socket determine almost everything about day-to-day comfort.
- Shrinker — A tight compression sock worn on the residual limb to reduce post-surgical swelling and shape the limb for prosthetic fitting.
- Sock ply — Prosthetic socks layered inside the socket to fill volume as the residual limb shrinks. The higher the sock count, the more volume the socks are filling; 10 ply usually triggers a socket modification.
- Definitive socket — The stable, long-term socket a patient receives once limb volume has stopped changing significantly.
- Pylon — The straight shaft (like the tibia) between the socket and the foot in lower-limb prostheses.
- Pistoning — The prosthesis sliding up and down on the residual limb during walking, usually caused by loose socket fit. A common source of friction and skin irritation.
- Mechanical knee — A prosthetic knee that functions as a hinge, stabilised by the user’s own muscle activity (particularly the glutes).
- Microprocessor knee — A prosthetic knee with electronic sensors and hydraulics that provide built-in stability in real time.
- Myoelectric prosthesis — A prosthesis (currently most common for arms and hands) that uses electrodes on the user’s muscles to trigger movement in the prosthetic hand.
- Rotator — A small device on a prosthetic knee that lets the lower leg rotate so the foot can rest on the opposite thigh — useful for putting on socks, shoes, and pants.
- Shower leg — A water-safe backup prosthesis built from an older socket, a pylon, and a grippy rubber foot, used for transfers into and out of showers and baths.
- Running blade — A specialised prosthesis designed for running and other athletic activities.
- Hemi Walker — A triangular one-sided assistive device that provides a wider base of support than a single-point cane.
- Pre-prosthetic gait training — PT work done before (or while) walking, focused on weight shifts, stance alignment, and posture over the prosthesis.