['Knee cartilage defects represent a socioeconomic burden and may cause lifelong disability. Studies have shown that cartilage defects are detected in approximately 60% of knee arthroscopies. In clinical trials, the majority of these patients are excluded. This study investigates whether patients included in randomized controlled trials (RCTs) represent a selected group compared to general cartilage patients.', 'Published randomized clinical trials on cartilage repair studies were identified (May 2009) and analyzed to define common inclusion criteria that in turn were applied to all patients submitted to our cartilage repair center during 2008. Patient-administered Lysholm knee score was used to evaluate functional level at referral. In addition, previous surgery and size and localization of cartilage defects were recorded.', 'Common inclusion criteria in the referred patients and patients included in the published RCTs were single femoral condyle lesion, age range 18 to 40 years, and size of lesion range 3.2 to 4.0 cm(2). Six of 137 referred patients matched all the 7 RCTs. Previous cartilage repair and multiple lesions were associated with decreased Lysholm score (P < 0.002). Lysholm score was independent of age, gender, and time of symptoms from the defect.'] Are knee Cartilage Defect Patients Enrolled in Randomized Controlled Trials Representative of Patients in Orthopedic Practice?