Prosthetic feet and knees

Question 1

Single axis feet:
Indications:
1.
2.
Advantages:
1.
2.
3.
4.
5.
Disadvantages:
1.
2.
3.
4.
5.
6.

Answer 1

Indications:
1. Simplicity
2. Low level ambulators
Advantages:
1. Rapid foot flat
2. Durable
3. Inexpensive
4. The plantar flexion capability provides increased knee stability at heel strike and foot flat and may lessen the difficulty of descending inclines
5. Plantar flexion resistance can be varied
Disadvantages:
1. Rigid forefoot
2. Not energy efficient gait
3. Increased maintenance due to moving components
4. Increased weight.
5. Less cosmetic
6. Increased cost

Question 2

SACH feet:
Indications:
1.
Advantages:
1.
2.
3.
4.
Disadvantages:
1.
2.
3.

Answer 2

Indications:
1. Knee instability
Advantages:
1. Lightweight
2. Minimal Maintenance
3. Good shock absorption for moderately active patients
4. No moving parts
Disadvantages:
1. Limited PF and DF adjustability
2. Heel cushion deteriorates over time
3. Rigid forefoot; not energy efficient

Question 3

Multi-Axial feet:
Indications:
1.
Advantages:
1.
2.
3.
Disadvantages:
1.
2.
3.
4.
5.

Answer 3

Indications:
1. Uneven surface
Advantages:
1. Reduces stresses/torque on residual limb
2. Allows motion in all planes
3. Adjustability
Disadvantages:
1. Cost
2. Increased maintenance
3. Increased weight
4. Decreased cosmesis
5. May provide less stability than other feet on smooth surfaces

Question 4

Flexible Keel feet:
Indications:
1.
Advantages:
1.
2.
3.
Disadvantages:
1.
2.
3.

Answer 4

Indications:
1. New or low level ambulators
Advantages:
1. Smooth/easy rollover
2. Provides increased ground compliance and stability
3. Decreased maintenance (good durability)
Disadvantages:
1. Limited push off
2. Poor cosmesis
3. Heaviest foot

Question 5

Dynamic response feet:
Indications:
1.
Advantages:
1.
2.
3.
4.
Disadvantages:
1.
2.

Answer 5

Indications:
1. Higher activity level
Advantages:
1. Mimics push off/smoother, more efficient gait
2. Lightweight
3. Durable
4. reduces impact forces and stress of sound side
Disadvantages:
1. Cost
2. Stiff keel for lower level activities

Question 6

Single axis knees: (constant friction)
Indications:
1.
2.
Advantages:
1.
2.
Disadvantages:
1.
2.

Answer 6

Indications:
1. Low level ambulators
2. Exoskeletal prostheses
Advantages:
1. Inexpensive
2. Durable
Disadvantages:
1. Amputee must be able to control
2. Single walking speed only

Question 7

Stance control knees:
Indications:
1.
2.
Advantages:
1.
2.
Disadvantages:
1.
2.

Answer 7

Indications:
1. General debility
2. poor balance or hip control
Advantages:
1. Stance stability
2. Weight-activated friction break
Disadvantages:
1. Delayed swing
2. Must unload completely to sit

Question 8

Manual locking knees:
Indications:
1.
2.
Advantages:
1.
Disadvantages:
1.
2.

Answer 8

Indications:
1. Last resort
2. Severe instability
Advantages:
1. Maximum stability, no knee flexion
Disadvantages:
1. Inefficient gait – leads to hip hiking, vaulting or circumduction
2. Awkward sitting

Question 9

Polycentric knees:
Indications:
1.
2.
Advantages:
1.
2.
3.
Disadvantages:
1.
2.
3.

Answer 9

Indications:
1. To enhance stability
2. Knee disarticulations
Advantages:
1. Inherently stable
2. Moves knee center posterior and proximal
3. Shortens during swing for easier toe clearance
Disadvantages:
1. Weight
2. Maintenance
3. Cost

Question 10

MPK, fluid-controlled (Hydraulic, pneumatic) knees:
Indications:
1.
Advantages:
1.
Disadvantages:
1.
2.
3.

Answer 10

Indications:
1. Variable cadence
Advantages:
1. Stance and swing control
Disadvantages:
1. Weight
2. Maintenance
3. Cost