Osteoarthritis, a degenerative rheumatic disease, is by far the most common form of arthritis and the main cause of pain, impairment and disability in older people. It is characterized by focal loss of articular cartilage, subchondral osteosclerosis, formation of osteophytes at the edge of the joint and remodelling of the shape of the joint with bony enlargement of the affected joints, hypotrophy of the surrounding muscles and hypertrophy of the surrounding fat tissue. Synovitis in osteoarthritis is usually not manifested clinically, but it significantly contributes to the pain and advancement of osteoarthritis. The knee is the most affected joint, followed by the hip. The diagnosis is primarily made clinically, with both conventional radiography and laboratory work-up not necessary except in patients with atypical manifestations. Treatment of hip and knee osteoarthritis is divided into non-pharmacological, pharmacological and surgical. Obesity is a chronic disease associated with increased mortality, and it affects almost every organ and tissue in the body. It is a significant systemic and local risk factor for osteoarthritis with the strongest association with knee osteoarthritis and is one of the few modifiable risk factors for the onset and progression of osteoarthritis.