Objective. The objective of this study was to evaluate the incidence of radiographic osteoarthritis in the operated knee in comparison with the contralateral knee ten years after a bone-tendon bone patellar autograft ACL-reconstruction and to evaluate to which level patients regain activity ten years after reconstruction. Methods. Fifty-three patients with ACL instability were operated arthroscopically using the central third of the patellar tendon as a bone-tendon-bone autograft. At a minimum of 10 year follow up 28/44 patients matched the inclusion criteria and could be reached for follow-up. Evaluation included a patient satisfaction evaluation using a Visual Analog Scale, physical examination (International Knee Documentation Committee score, Tegner score, Lysholm score, KT-1000 stabilometry) and a radiological evaluation (Kellgren and Fairbanks classification). Results. The patients' satisfaction, at a mean of 10,3 year follow-up, measured with a VAS score (0-10) was high with a mean of 8.5 (range 4 to 10). The KT 1000 arthrometer laxity measurements revealed in 55% of the patients an A rating (1-2 mm), in 29% a B rating (3-5 mm) and in 16% a C rating (6-10 mm). According to the Tegner score 54% of the patients were able to perform at the same activity level as pre-operatively. The mean pre-operative Tegner score was 6.8 and the mean post-operative Tegner score was 6.0 at final follow up. The Lysholm score showed satisfactory results with a mean of 91 points (range 56 to 100). According to the Kellgren and Fairbank classifications, there is a significant difference (p < 0.05) in development of OA between the ACL injured and subsequently operated knee in comparison to the contralateral knee. Conclusion. The patellar BTB ACL reconstruction does not prevent the occurrence of radiological OA after 10 years but does help the patient to regain the pre-operative level of activity.