ANTERIOR KNEE LAXITY AND LOSS OF EXTENSION AFTER ANTERIOR CRUCIATE LIGAMENT INJURY

This study was performed to examine the relationship between knee exte nsion loss and the length of time after injury. We also wanted to comp are anterior laxity in anterior cruciate ligament-injured knees in the early and late stages of injury. Loss of knee extension was measured in 81 patients with anterior cruciate ligament injury using lateral ra diography with the injured leg relaxed and elevated. Extension loss wa s defined as the difference in maximal extension angle between the inj ured and uninjured knees. Average loss of extension was 3.6 degrees in the 17 knees in which the anterior cruciate ligament had been torn 3 weeks or less before examination (the acute injury group) and 0.6 degr ees in the 64 knees in which the anterior cruciate ligament had been t orn more than 3 weeks before examination (the chronic injury group). T he extension loss in the acutely injured knees was significantly great er compared with that in the uninjured knees and in the chronically in jured knees. Arthrometric measurements using the KT-1000 arthrometer w ere reliable to diagnose an acute tear. There was no correlation betwe en the degree of extension loss and arthrometric anterior knee laxity measurements. In 12 patients, the initial extension deficit in the ear ly stage of injury significantly resolved with time, and manual maximu m arthrometric measurements of anterior knee laxity improved spontaneo usly with time.