Transtibial Prosthetics

Question 1

If you decrease the heel lever and increase the toe lever it results in…?

Answer 1

Greater stability

Places GRF anterior to the knee promoting knee extension

Question 2

Socket adjustments to achieve decreased heel lever, increased toe lever

Answer 2

1. socket extension (angular)
2. socket posterior (linear)
3. foot plantarflexed (angular)
4. softer heel cushion/PF bumper during loading response

Question 3

If you increase the heel lever and decrease the toe lever it results in…?

Answer 3

Greater mobility

Places GRF posterior to knee promoting knee flexion

Question 4

Socket adjustments to increase heel lever, decrease toe lever

Answer 4

1. socket flexion (angular)
2. socket anterior (linear)
3. foot DF (angular)
4. stiffer heel cushion/PF bumper during loading response

Question 5

Prosthetic “bench alignment”

Answer 5

-socket flexed forward 5 degrees and slightly adducted

Question 6

Should pressure be uniform over the residual limb?

Answer 6

NO! It should be “total contact”, but pressure should not be uniform. The prosthetic should place pressure on areas that can handle it and relieve pressure from sensitive areas.

Question 7

Why are transtibial sockets placed in 5 degrees of flexion?

Answer 7

This places loading onto the patellar ligament.

Question 8

If a patient has poor knee control, how should the socket be positioned?

Answer 8

Extended or posteriorly

Question 9

If a patient has strong quads and is very active how should the socket be positioned?

Answer 9

Flexed or anteriorly

Question 10

How should you accomodate a knee flexion contracture?

Answer 10

Increase the socket flexion

Question 11

Why is the prosthetic foot placed medial relative to the socket?

Answer 11

Provides more stability and offloads the fibular head

Question 12

Why would you place a food in a more lateral position?

Answer 12

To increase the M/L stability during stance, BUT this increases pressure on the fibular head so BE CAREFUL!

Question 13

GRF/anatomic causes/prosthetic causes of insufficient knee flexion

Answer 13

GRF - placed too far anterior causing excessive knee extension
Anatomic causes: anterodistal pain, weak quads, poor balance, extensor spasticity, contracture
Prosthetic causes: socket extended too much, socket too posterior, ankle too much PF, heel cushion too soft, suspension interferes with knee flexion

Question 14

GRF/anatomical causes/prosthetic causes of excessive knee flexion (buckling)

Answer 14

GRF- too far posterior to knee joint causing excessive flexion
Anatomic: weak quads, knee flexion contracture
Prosthetic: socket too far anterior, socket too far flexed, foot too DF, heel cushion too rigid, prosthesis too long

Question 15

Causes during late stance for excessive knee flexion/insufficient knee flexion

Answer 15

Same as for early stance, except in late stance issues with heel height and heel cushion do not apply

Question 16

What prosthetic malalignments cause excessive lateral thrust?

Answer 16

• Socket too adducted
• GRF passes medial to the knee
• excessie lateral placement of the socket (foot inset)

Question 17

What prosthetic malalignments cause excessie medial thrust?

Answer 17

• socket too abducted

- medial displacement of the socket (foot outset)