Good muscle performance does not compensate instability symptoms in chronic anterior cruciate ligament deficiency.

A total of 167 patients with documented anterior cruciate ligament deficiency was examined preoperatively with laxity and isokinetic muscle strength measurements. Functional evaluation with Lysholm knee and Tegner activity level scores were done. Antero-posterior (AP) knee laxity correlated negatively with Tegner activity level (NS), and insignificantly with Lysholm knee score. A marginal correlation was found between the Lysholm score and muscle strength. Patients were divided into four groups depending on whether their AP laxity was greater or less than 20 mm and whether their quadriceps strength was greater or less than 85% of their control knee. No difference in the Lysholm or Tegner scores between the groups was observed. As a conclusion it seems that even a relatively good muscle performance does not compensate severe instability symptoms.