Osteoarthritis (OA) of the knee is a progressive disease that ultimately damages the entire joint. Knee OA should initially be treated conservatively, but surgery should be considered if symptoms persist. Surgical treatments for knee OA include arthroscopy, osteotomy and knee arthroplasty; determining which of these procedures is most appropriate will depend on several factors, including the location and severity of OA damage, patient characteristics and risk factors. Arthroscopic lavage and debridement do not alter disease progression, and should not be used as a routine treatment for the osteoarthritic knee. Bone marrow stimulation techniques such as microfracture are primarily used to treat focal chondral defects; the evidence for the use of these techniques for knee OA remains unclear. The goal of osteotomy for unicompartmental knee OA is to transfer the weight load from the damaged compartment to undamaged areas, delaying the need for joint replacement. This procedure should be considered in young and active patients who are not suitable candidates for knee arthroplasty. For patients with severe OA, total knee arthroplasty can be a safe, rewarding and cost-effective treatment. In selected patients with isolated medial or patellofemoral OA, unicompartmental knee arthroplasty and patellofemoral replacement, respectively, can be successful.