23 acute midsubstance ruptures of the posterior cruciate ligament were treated by primary suture. 20 patients returned for follow-up. Four of them had an isolated rupture of the PCL. The remaining 16 patients had sustained combined injuries to ligaments, including eight total ruptures of the anterior cruciate ligament. All ruptured ligaments were sutured. At follow-up (median = 5.5, range 3-10 years) median knee score according to Lysholm was 81 (range 53-100). Five were rated excellent, six good, three fair and six poor. KT-1000 arthrometer measurements revealed a posterior instability of between 5 and 10 mm in five patients and below 5 mm in 14 patients. Thus, in most patients, some instability remained in spite of operative treatment.