We describe a new method for the reconstruction of ruptures of the patellar ligament or the quadriceps tendon, using the flexible open-weave polyester Leeds-Keio prosthetic ligament. Of 25 operations performed since 1985, we were able to review 18 patients (19 knees) with a mean follow-up of 3.5 years (3 to 6.5). No patient had required immobilisation of the knee after operation and the average period to return to normal activities without a walking aid was 10.5 weeks. The average range of motion was 146 degrees, and four patients could squat fully in the Japanese style. There was an extension lag (< 10 degrees) in only four patients; eight patients had some patellar crepitus which was mildly painful in three. There were no cases of infection, persistent joint effusion or rerupture of the extensor apparatus.