Ratio of hamstring to quadriceps femoris muscles' strength in the anterior cruciate ligament insufficient knee. Relationship to long-term recovery.

The purposes of this study were 1) to investigate the peak torque and total-work ratios of hamstring to quadriceps femoris muscles' (HQ) in 41 subjects (27 male, 14 female; means age = 35 years) with an anterior cruciate ligament insufficient knee (ACLIK) and 2) to determine the relationship between HQ ratios and long-term subject outcome. Quadriceps femoris and hamstring musculature strengths of both legs were measured at follow-up with an isokinetic dynamometer, and peak torque values were recorded at lower (60 degrees/sec) and higher (180 degrees/sec) speeds. Maximal isometric extension and flexion outputs were measured at a 60-degree knee-flexion angle. Three standardized knee-scoring scales were used to determine the overall outcome of the ACLIK. High intersubject variability of the HQ ratios (range = 23%-205%) was observed in all strength tests, including tests of healthy knees. The injured knee of all subjects had a higher HQ ratio (46%-95%) in every test than the healthy knee (42%-85%). The HQ ratio difference between knees was significant at the isokinetic higher speed (p less than .05) and for the total-work (p less than .05) tests because of the weak quadriceps femoris muscle of the injured knee. Outcome scores did not differ significantly between the groups with low, optimal, or high HQ ratios of the ACLIK but were significantly better in subjects whose HQ ratio of the injured knee was similar to that of their uninjured knee.(ABSTRACT TRUNCATED AT 250 WORDS)