There are several options available for management of the middle-aged arthritic knee. Arthroscopic techniques continue to evolve, but the true natural history of the arthritic process is probably not altered. Good to excellent short-term results can be expected with proper patient selection. Patient counseling is important in order to discuss the nature of the underlying disease process, the limited goals of the arthroscopic procedure, and the possible need for further surgery. Proximal tibial osteotomy for the treatment of medial compartment osteoarthritis can be effective for as long as 15 years. There is a deterioration of results over time that can often be correlated to the degree of correction achieved. Strict selection criteria can maximize success. Revision surgery to total knee replacement, albeit technically difficult, is a viable option with results similar to primary TKR. Unicompartmental knee arthroplasty remains a controversial procedure as its indications continue to evolve. Good to excellent results can be expected in 80% to 90% of patients at 10 years follow-up. Unicompartmental knee arthroplasty occupies a special niche in the treatment of unicompartmental osteoarthritis and supplements total knee replacement and high tibial osteotomy surgery.