INTRODUCTION

Traumatic injuries of the knee ligaments present in various degrees of severity from interstitial sprains to complete ligament tears. The femoral insertion of the anterior cruciate ligament (ACL) is susceptible to post-traumatic ischemic changes secondary to interrupted vascular supply from the tibial insertion. In comparison, the posterior cruciate ligament (PCL) has more extensive vascularization from the posterior geniculate arteries, which allows better healing of these injuries with fibrous scar tissue. MRI of a scarred PCL injury shows lower than normal signal intensity, which post-traumatic changes in signal intensity are well described in the literature. In my personal experience with more than 5500 MR examinations of the knee, PCL traumatic injuries secondary to motor vehicle accidents or sports injuries are a frequent finding. Many of these patients are completely asymptomatic for articular instability.

MATERIAL AND METHODS

From November, 1994, to July, 1997, a direct MR follow-up was proposed to patients with PCL traumatic tears. Only the patients examined in our hospital were included in this study because the MR scans were performed using the same unit, matrix, FOV, slice thickness and sequences. Twenty patients had acute traumatic injuries of the PCL. Four were not examined because of an additional traumatic episode and four were not included because they were operated on. Ten patients were thus enrolled: three women and seven men whose age ranged 23 to 41 years (mean: 35.7). MR follow-up ranged 9 to 36 months (average: 14.2).

RESULTS

At the first MR examination, PCL tears were classified as follows: Gross class II (1 patient) and Gross class III (9 patients). Follow-up MRI showed no PCL in 2 patients (similar to ischemic degeneration in complete ACL tears), focal interligament changes within a continuous PCL in 2 patients and normal PCL in 6 patients. The trauma was caused by a motor vehicle accident with the knee flexed in 8 patients and during hyperflexion in sports activity (skiing or soccer) in 2 patients. Five patients presented with knee instability and subjective complaints, such as pain and difficulty in climbing stairs, walking, running, or performing sports activity. Follow-up MRI showed natural repair of the PCL traumatic injury in 5 patients, with absolutely no knee instability.

CONCLUSION

Even though the number of patients in this study is limited, follow-up MRI confirms the possibility of scar tissue repair in PCL post-traumatic injuries, supporting primary conservative treatment.