Temporal changes in posterior laxity after isolated posterior cruciate ligament injury: 35 patients examined by stress radiography and MRI.

We examined the temporal changes in posterior laxity and MRI findings in acute isolated posterior cruciate ligament (PCL)-injured knees. 35 patients with acute isolated PCL injuries who attended our clinic within 10 weeks of an injury underwent nonoperative treatment, and were chronologically evaluated for posterior laxity and MRI. We divided them in 3 groups, as regards the evolution of laxity and MRI findings. In 20 patients, the degree of posterior laxity was slight throughout the observation periods. In 9 patients, who had severe posterior laxity on their initial visit, the laxity had improved markedly 6 months after injury and did not deteriorate. In 6 patients the severe posterior laxity did not improve during the study. 4 patients whose PCL on MRI was seen as a continuous swollen band having high signal intensity and showed consistently good stability or even an improvement. We conclude that acute isolated PCL injuries with a continuous swollen band on MRI should be treated conservatively for at least 6 months after injury, even if the posterior laxity is severe initially.