Fifty-two patients with osteochondritis dissecans lesions were evaluated after 7-25 years after excision of a partially detached (grade III) fragment or loose (grade IV) fragment from the medial femoral condyles. Average follow-up time was 17.2 (range 7-25 years). Two homogenic groups based on special inclusion criteria were formed; 31 patient was in the first and 21--in the second group. The only difference between the groups was the age; the age average in the first group was--25.6 years (range 15-35 years), and -45.2 years (range 35-55 years) in the second group. Patients were evaluated through ICRS (International Cartilage Repair Society), modified HSS and KOOS (Knee injury and osteoarthritis Outcome score) scales, and with X-rays. Evaluation with the ICRS, modified HSS and KOOS rating scales for osteochondritis dissecans revealed in 9 cases (17%) good results, 32 cases (62%)--fair, and 11 cases (21%)--failure results. Final ICRS and modified HSS evaluation showed statistically significantly better results in the younger patient group at the 21 years (p < 0.04). At an average 17.2 year follow-up X-rays and KOOS evaluation form showed initial and second-degree (according to Ahlbäck) osteoarthritis signs in the knees. The long-term results of the natural history of osteochondritis dissecans are extremely poor. Consequently, we recommend autologous osteochondral grafting for the replacement of the osteochondritis dissecans defects in the knee joint.