Transfemoral knees

This knee is computerised and involves a microprocessor that receives information from sensors inside the knee and foot about the position of the knee and ground reaction forces (Spires, Kelly & Davis, 2013; Murphy, 2013). This data is used by the microprocessor to adjust the knee and control the rate at which the hydraulic valves open and close, for the most appropriate gait patterns (Murphy, 2013). These knees have a stumble recovery mode, are able to adjust to various cadences, and allow for reciprocal gait while descending stairs (Spires, Kelly & Davis, 2013). Appropriate for K3 and K4 levels (Murphy, 2013).

Polycentric knee

Locking knee

Stance control knee

Constant friction, single axis knee

Fluid controlled knee

Microprocessor knee

This knee is locked in order to prevent flexing (Murphy, 2013). The advantage is that the knee is stable and secure, however the disadvantage is that the individual’s gait is affected, as hip hiking and circumduction are required in order to clear the leg (Murphy, 2013; Spires, Kelly & Davis, 2013).

The stability of this knee is achieved through the alignment within the knee, and the alignment of the knee within the total prosthesis (Murphy, 2013). The knee will bend when weight is placed through the forefoot or toe and will lock when weight is beared through the heel (Spires, Kelly & Davis, 2013). The disadvantage of this knee is the possibility for the wearer to establish a tendency to kick the knee out hard and fast, and slam the heel of the foot down when going into stance phase for security that the knee is locked (Murphy, 2013).

This knee has a weight activated stance feature that is activated when a certain amount of weight is placed through the prosthesis, which causes the knee components to restrict flexion (Murphy, 2013). De-weighting the knee releases the locking mechanism and allows the knee to bend (Murphy, 2013). The advantage is this allows for stability of the knee when weight bearing, and the disadvantage is the need for adequate weight bearing onto the prosthesis in order for the lock to be activated (Murphy, 2013; Spires, Kelly & Davis, 2013).

This knee has a single axis hinge design and a constant friction feature. The stability of the knee depends on the relation of the trochanter-knee-ankle (TKA) line to the centre of the knee axis (Murphy, 2013). If the line is more anterior, the knee is more stable but with greater difficulty to flex the knee (Murphy, 2013). If the TKA line is more posterior to the knee axis, the greater the tendency is of the knee to flex (Murphy, 2013). The disadvantage of the constant friction knee is the fixed cadence (Murphy, 2013). Predominantly indicated for K1 and K2 level ambulators (Spires, Kelly & Davis, 2013).

This knee has a fluid control system, made up of a cylinder with a piston and fluid, which is either pneumatic (air) or hydraulic (liquid) (Spires, Kelly & Davis, 2013). As the pistons move, the control valves maintain varying degrees of resistance depending on the angle of the knee, which allows for variances in cadence (Murphy, 2013). The disadvantages are the knees are heavier and more expensive than mechanical friction knees, although are lighter and cheaper than microprocessor knees (Murphy, 2013).

References:

Medical expo (2017). Polycentric prosthetic knee joint / 1 / standard / adult. Retrieved from: http://www.medicalexpo.com/prod/oessur/product-74948-467934.html

Murphy, D. (2013). Fundamentals of Amputation Care and Prosthetics. New York: Demos Medical Publishing

NZALS (2017). Knee joints. Retrieved from: http://www.nzals.co.nz/products/categories/knee-joints

Orthoeurope (2017). Single axis knees. Retrieved from: http://www.ortho-europe.com/product/single-axis-knees/

Spires, M. C., Kelly, B., & Davis, A. (2013). Prosthetic restoration and rehabilitation of the upper and lower extremity. New York: Demos Medical Publishing

Transfemoral Knees

Transfemoral Suspension

Transtibial Suspension

Transfemoral Sockets

Transtibial Sockets

Prostheses