MT: Prosthetic Knee Designs

Question 1

Knee Functions to Replace

Stability

Answer 1

• prevent knee collapse during stance phase
• safety first

Question 2

Knee Functions to Replace

Mobility

Answer 2

• allow movement during swing phase
• efficiency second

Question 3

Stability in Stance

Answer 3

• ensure extension at heel strike
• maintain extension (prevent buckling any time px is loaded)

Question 4

Mobility in Swing

Answer 4

• initiate flexion
• control rate, magnitude of fl/ex
• ensure full extension

Question 5

Swing Control Option - Resistance

Answer 5

• flexion seing resistance in early swing (limits heel rise)
• extension swing resistance in mid and late swing: affects toe clearance and terminal impact

Question 6

Resistance Cautions

Answer 6

• timing of flexion/extension affects toe clearance
• swing resistance does not prevent knee collapse when prosthesis is laoded

Question 7

What does insifficient resistance cause

Answer 7

• excessive heel rise: prolongs swing phase on the px side
• terminal impact: abrupt often audible, stop extension just prior to IC

Question 8

What does excessive resistance cause

Answer 8

• instability at IC due to flexed knee

Question 9

Swing Control Option - Assist

Answer 9

• increases knee extension force during swing
• late swing: aids full knee extension at IC
• early swing: resists knee flexion
• mid swing: may limit toe clearance

Question 10

Stance Phase Control

Answer 10

• resists knee flexion during stance
• provides stability during loading of prosthesis; especiallu important during loading