The relationship of knee and ankle weakness to falls in nursing home residents: an isokinetic study.

The strength of the knees and ankles of a group of nursing home residents with a history of falls was compared to age-matched controls. Peak torque (PT) and power (POW) were recorded at two limb velocities (60 degrees/s and 120 degrees/s) on a Cybex II Isokinetic dynamometer for four muscle groups: knee extensors, knee flexors, ankle plantar flexors and ankle dorsiflexors. The PT and POW of fallers were significantly decreased for all four muscle groups in comparison to controls, with the ankles showing the greatest decrements. Although POW in fallers was significantly lower at the higher velocity in both joints, the decrease was most prominent in the ankles. Dorsiflexion POW production in fallers was the most affected of all the motions (7.5 times less than the control value). At the higher, more functional limb velocities, ankle weakness particularly involving the dorsiflexors appears to be an important factor underlying poor balance.