Contraindications for MRI (pregnancy, metallic implants, etc.) Daily use of drugs with a putative effect on the patellar tendon in the preceding year (e.g. fluoroqinolones and statins) Knee surgery in the history of the index knee Previous patellar tendon rupture of the index knee Local injection therapy with corticosteroids in the preceding 12 months Daily exercise therapy with a minimum duration of 4 weeks in total in the preceding 12 months Acute knee or patellar tendon injuries Inability to perform an exercise program Participation in other concomitant treatment programs Signs or symptoms of other coexisting knee pathology on physical examination (such as joint effusion and joint line tenderness) or additional diagnostics (Chondral lesion of the patella or trochlea on MRI or prepatellar bursitis on US).