Survey of Polycentric Knee Mechanisms

Question 1

Polycentric knees require a dampening mechanism to function properly.

Answer 1

False

Question 2

The frame type polycentric endoskeletal components are designed to provide the axis mechanism at the knee. In order to be complete, however:

Answer 2

A dampening mechanism must be added.

Question 3

As far as the alignment of a polycentric knee is concerned:

Answer 3

Proper orientation varies widely. It is important to follow specific manufacturers guidelines in bench aligning polycentric knee designs

Question 4

Some polycentric knees are very suitable for use with the knee disarticulation amputation because the distance from the knee articulation to the top of the knee unit itself is only 18 mm.

Answer 4

True

Question 5

Polycentric knee units can incorporate:

Answer 5

• Constant friction dampening mechanism where the swing rate can be adjusted to the patient’s single cadence.
• A feature that allows the instant center of rotation curve to be altered by the adjustment of an extension stop.
• The capability of allowing from 110 to 160 degrees of flexion , depending on the unit selected.
• Distances from the knee articulation to the top of the knee unit that vary so much in the overall distance from the knee center to the socket that not all are appropriate fro the knee disarticulation patient, but can function well for the medium to long transfemoral levels.