Mechanical friction knees are lightweight and relatively inexpensive due to their simplicity.

The friction (resistance to bending) in the knee joint is typically adjusted by tightening a screw or bolt. The same amount of friction is applied to the knee regardless of whether it is flexing or extending.

A spring is often used to overcome some of the friction when the knee extends (straighten). This speeds up the knee in the swing phase of gait.


  • Simplicity
  • Durable & robust
  • Can be made lighter and smaller.
  • May be used over one axis of rotation (monocentric knees) or multiple axes (polycentric knees).
  • Inexpensive


  • Friction reduces with wear & may need frequent adjustment.
  • Constant friction design does not adapt to different walking speeds.
  • May become noisy when wearing.

Common Components

Otto Bock