Loss of the knee extensor mechanism results in a change of normal knee joint alignment and functional anteroposterior instability. In patients with neglected or chronic patellar tendon rupture, advanced degenerative change of the knee joints may develop at the later stage. We present a case of a 64-year-old man with chronic left patellar tendon rupture and 10-cm proximal patella migration associated with advanced osteoarthritis of the knee. Total patellectomy and simultaneous total knee arthroplasty (TKA) relieved his symptoms and disability successfully. His left knee still did well at 7-year follow-up.