Rupture of the ACL is an extremely common sports injury and its incidence is currently rising.3,4,28 Various mechanisms of injury have been described as causing ACL injuries.3, 4, s, 28 Rupture of the patellar tendon, on the other hand, is rare. In the Kannus and Jozsa 12 study of 891 tendon ruptures, less than 6% of the injuries involved the patellar tendon. Clinicians agree that this injury occurs predominantly in the under-40 age group because in later life ruptures of the extensor mechanism typically involve the quadriceps tendon. Patellar tendon ruptures are associated with intratendinous degenerative changes (e.g., jumper's knee) (Refs. 10, 14, 25; G. J. Lane et al., unpublished data, 1994).In 1980, Baker reported a case in which a 24-year-old basketball player simultaneously ruptured the ACL, medial collateral ligament (MCL), and patellar tendon. In 1991, Rae and Davies 23 published what they considered to be the first report of the same injury combination in a 25-year-old trampoline gymnast. Rupture of the patellar tendon and the ACL without involvement of the MCL (Cases 2 and 3) has not, to our knowledge, been reported previously.We analyzed six cases collected from different centers. The treatment modes have varied widely. In each case, both the preoperative assessment and subsequent surgery were performed by at least one of the authors. We made a special effort to clarify the exact mechanism of injury in each case based on the patient's recollection, and we conducted interviews of bystanders, when possible. We more accurately scrutinized one of the injuries, which occurred during a professional football game, by using frame-toframe analysis of the existing videotape. CASE HISTORIESCase 1 A 36-year-old recreational soccer player injured his knee jumping for the ball (Table 1). On landing, he heard two pops as his knee collapsed under him. He had a positive Lachman test and a grade 3 opening on valgus stress on examination.During the operation, surgeons were surprised to find a midsubstance tear of the patellar tendon. Primary repair of the patellar tendon, as well as medial and lateral meniscal repairs, distal reattachment of the MCL, and ACL reconstruction with a prosthetic ligament were performed during the same procedure.After surgery, a hinge brace that limited motion was applied to the knee for 8 weeks. Rehabilitation was then intensified. At followup, 18 months after surgery, the athlete had full knee extension and good return of quadriceps muscle strength. Knee flexion had diminished by 15° and radiographs showed a 20% shortening of the patellar tendon. Results of the Lachman and pivot shift tests were negative.Case 2 A 15-year-old high school athlete injured her right knee during a long jump (Fig. 1). She heard a pop when she landed and subsequently was unable to walk. She was taken to the nearest hospital, where a patellar tendon rupture was diagnosed and a primary repair was performed. After surgery, the leg was immobilized in a long leg cast for 6 weeks.