Knee flexor and extensor strength in ankle instability

The purpose of this study is to investigate knee flexor and extensor strength in subjects with unilateral ankle instability, with the specific aim of determining whether strength deficits exist. lsokinetic knee flexor and extensor torques were assessed in 16 healthy control subjects and 17 subjects with unilateral ankle sprain injury. Subjects were assessed using isokinetic apparatus (Kin-Kom) at speeds of 60 degrees/sec. Absolute peak torque, time to reach peak torque and angle of peak torque values were compared between control and injured groups as well as dominant and non dominant limbs within groups. Statistical analysis indicated peak torque production is reduced in quadriceps (8.9%, p<0.05) and hamstring muscles (10.1 %, p<0.05) of the injured limb. Time to reach peak torque was increased in quadriceps of the non dominant limb in the injured group (15.7%, p<0.05). Angle of peak torque of quadriceps of dominant injured limb was greater than the control group (10.8%, p<0.001). The findings of this study suggest ankle instability following ankle sprain is associated with deficits in knee flexor and extensor strength of the injured limb. These changes in muscle strength highlight the significance of extending assessment beyond the side and site of injury. Moreover, we emphasise strength training of knee flexors and extensors in the rehabilitation program for ankle instability.