Knee Hyperextension
Patients with weakness in the muscles that control the knee may hyperextend their knees to improve stability when standing or walking. For patients with chronic high tone contractures of the calf muscles, excess ankle plantarflexion can drive the knee back into hyperextension or a combination of hyperextension and toe walking. An assessment of the patient’s muscle tone, level of voluntary control and range of movement of the entire kinetic chain is required to determine the factors leading to Hyperextension.
• A snapping back of the knee during weight-bearing
• Can vary from mild and inconsistent to very pronounced and constant
• Caused by weakness or high tone:
- When muscle strength or control is inadequate, hyperextension of the knee gives the patient a stable position that requires less muscle strength to maintain
- High tone ankle plantarflexion drives the knee into hyperextension-degree of hyperextension proportional to tone
• May also have pronated or supinated foot
Brace Selection for Knee Hyperextension
Within each level of involvement, there are recommended brace solutions.
- Occasional hyperextension
- Soft and not distinct
- Can control when focused
- Frequent hyperextension
- Distinct but not forceful
- Can reduce but not eliminate when focused
- Constant hyperextension
- Sudden and forceful
- Little or no voluntary control
