Patients' complaints on limitations in activities of daily living (ADL) and sports are possible signs for various injuries of the knee joint. These complaints can be easily assessed by the patient using a questionnaire with visual analogue scale (VAS) responses. A German translation of the English questionnaire concerning knee complaints [4] has been validated and tested for clinical use. It consists of 28 questions. For the statistical analysis, an overall score (VAS score) of the questionnaire was determined. The validation included an expert evaluation on the content of the questionnaire, a test for the reliability, a comparison with subjective knee scoring systems (Cincinnati score, Lysholm score) and a test on VAS score results in patient groups with various knee injuries (discrimination of patients). For the evaluation of operative treatment results, the responsiveness of the questionnaire was tested in patients undergoing arthroscopic meniscus surgery and anterior cruciate ligament reconstruction. The investigation was conducted prior to the operation, 2, 6, 12 and 24 weeks after surgery for both groups and also 36 weeks after surgery for the cruciate ligament patients. Interviews conducted with knee surgeons (so-called knee experts) revealed that 85% judged the questionnaire as being acceptable for clinical use. The reliability of the VAS score for healthy individuals was r = 0.86. The reliability for patients in a postoperative rehabilitation programme was r = 0.92. By means of the VAS score we were able to assess the extent of limitations in knee function in various patient groups with meniscus lesions, insufficiency ot the anterior and posterior cruciate ligaments and chondromalacia.(ABSTRACT TRUNCATED AT 250 WORDS)