Knees that have the most alignment stability in stance
manual locking
Knee type closest to anatomical knee
polycentric
How does a manual locking knee work?
- pt stands up and it locks
- stays locked until they manually unlock it
Disadvantage to a manual locking knee
- knee locked out in gait
- poor energy conservation
*sacrifices mobility for stability
What are the knee types we talked about?
- manual locking
- outside (external hinges)
- conventional (single-axis)
- polycentric (multiple-axis or 4 bar)
- hydraulic and pneumatic
- microprocessors
How do external hinge knees work?
- doesn’t automatically lock
- more free swinging
Who gets external hinge knees?
knee disarticulations
single axis knee: What is involved with swing control?
- extension aid
- friction
How does an extension aid work?
If knee is flexed and unloaded, the knee will extend in anticipation of heel strike
Problems with extension aid
- amputee can’t adjust speed
- extension aid doesn’t change speed
How does friction help with the extension aid?
gives control to extension so it doesn’t snap out too quickly
How does a polycentric knee replicate motion better than a single axis knee?
pylon is able to move more posterior
hydraulic and pneumatic knees: fluid during flexion/extension
- knee flexion compresses the fluid
- When unloaded, compressed fluid springs back
Major benefit to hydraulic/pneumatic knees
can adjust to cadence
pneumatic knees: fluid and temp
- contains air
- unaffected by temp changes
hydraulic knees: fluid and temp
- contains water or oil
- temp affects fluid viscosity
How do microprocessor knees work?
- read sensors in the shoe
- know what phase of stance/swing they’re in
- improved gait with less training required
microprocessor knees: cost
expensive, but not as high cost as before
C-leg =
computerized leg
c-leg and uneven terrain
recognizes and adjusts for uneven slopes
Which knees are the new standard?
microprocessors are becoming std for TF pts
