Osteoarthritis is a disabling joint disease characterized by noninflammatory degeneration of the joint complex (articular cartilage, subchondral bone, and synovium) that can have various causes, most notably advanced age and overuse. It mainly affects weight-bearing joints and joints that are heavily used, such as the hip, knee, hands, and vertebrae. Despite the widespread view that osteoarthritis is a condition caused exclusively by degenerative “wear and tear” of the joints, newer research indicates that there are various causes, including preexisting joint abnormalities, genetics, local inflammation, mechanical forces, and biochemical processes that are promoted by proinflammatory mediators and proteases. Major risk factors for osteoarthritis include advanced age, obesity, previous injuries, and asymmetrically stressed joints. In early-stage osteoarthritis, patients typically report a reduced range of motion, joint stiffness, and pain that is aggravated with heavy use. As the disease advances, persistent pain may also be present during the night and/or at rest. The diagnosis is predominantly based on clinical features and supported by radiological findings, as classic radiographic features of osteoarthritis do not always correlate with the patient's clinical symptoms or appearance. If lifestyle changes (e.g., moderate exercise, weight loss) fail to improve symptoms, pharmacotherapy is typically used for the management of active osteoarthritis. If these measures do not improve the patient's quality of life, surgical procedures such as arthroplasty may be necessary.
See also “Osteoarthritis of the hip and knee” for more specific information.
- Prevalence: most common joint disorder in the USA, affecting more than 20 million adults 
- Incidence: increases with age
- Sex: ♀ > ♂, especially in patients older than 50 years
- Incidence rates in specific joints: knee > hip > hand 
Epidemiological data refers to the US, unless otherwise specified.
- Modifiable risk factors 
- Nonmodifiable risk factors 
Osteoarthritis can be classified according to the underlying cause: 
- No identifiable underlying cause
- Can be localized or generalized
- Genetic factors of causation have been implicated, but not definitively proven.
- Secondary OA
Chronic mechanical stress on the joints and age-related decrease in proteoglycans → cartilage loses elasticity and becomes friable → degeneration and inflammation of cartilage ; → joint space narrowing and thickening and sclerosis of the subchondral bone 
Common clinical findings 
- Pain during or after exertion (e.g., at the end of the day) that is relieved with rest
- Pain in both complete flexion and extension
- Crepitus on joint movement
- Joint stiffness and restricted range of motion
- Morning joint stiffness usually lasting < 30 minutes
- Possible formation of varus deformity if the knee is affected ;
- Joints are usually asymmetrically involved, as opposed to rheumatoid arthritis.
- Findings in late-stage disease: constant pain (including at night) and a more severely restricted range of motion than during the early stages
Joint-specific findings 
- Heberden nodes: pain and nodular thickening on the dorsal sides of the distal interphalangeal joints, ♀ > ♂
- Bouchard nodes: pain and nodular thickening on the dorsal sides of the proximal interphalangeal joints , ♀ > ♂
- Rhizarthrosis: osteoarthritis of the first carpometacarpal joint, between the trapezium and the first metacarpal bone
- Hallux rigidus: osteoarthritis of the first metatarsophalangeal joint, between the first metatarsal and the first proximal phalanx; characterized by hypertrophy of the sesamoid bones
- See also “Clinical features” in “ .”
Osteoarthritis is a clinical diagnosis
- Consider the diagnosis in patients ≥ 45 years of age with typical clinical features. 
- There are no specific diagnostic criteria. 
- If there is clinical doubt, consider imaging and additional testing to:
- Invasive procedures are not routinely recommended, but may be helpful in select circumstances, for example:
Osteoarthritis is often diagnosed based on the patient's history and the presence of typical clinical features. Radiographic signs often do not correlate with the patient's reported symptoms or clinical findings; therefore, imaging is usually used to support the diagnosis.
The presence of at least one of the , in addition to typical clinical features, supports the diagnosis of osteoarthritis.
First-line modality: radiography of affected joints
- Consideration: Multiple views are typically more accurate than a single view.
Other imaging modalities
Other modalities may be indicated if the diagnosis remains uncertain after radiography.
- Disadvantages: expensive, not as widely available as other imaging modalities, and the contrast can cause hypersensitivity or kidney injury
- Computed tomography: : may offer improved visualization of osteophytes and subchondral cysts, particularly in the hip joint, compared with radiography and MRI
Radiological signs of osteoarthritis 
- Irregular joint space narrowing
- Subchondral sclerosis: a dense area of bone (visible on x-ray) just below the cartilage zone of a joint that forms as a result of a compressive load on the joint
- Osteophytes (bone spurs): spurs or densifications that develop on the edges of the joint, increasing its surface area
- Subchondral cyst: a fluid-filled cyst that develops on the surface of a joint due to local bone necrosis induced by the joint stress caused by osteoarthritis
- Laboratory testing: Inflammatory markers (e.g., erythrocyte sedimentation rate, C-reactive protein) are usually normal in osteoarthritis.
- Arthrocentesis: Synovial fluid analysis usually does not show the presence of inflammation (white blood cell count< 2000 mm3). 
- Arthroscopy: may show a thickened capsule, synovial hypertrophy, and/or ulcerated cartilage
The differential diagnoses listed here are not exhaustive.
- Follow a stepwise approach to treatment: Start with nonpharmacological management, followed by pharmacological and/or surgical treatment if needed.
- Individualize treatment based on patient preferences, comorbidities, treatment goals, and available resources.
- Consider referral to physical therapy or occupational therapy.
- Educate patients about the disease and self-management techniques.
- Exercise: indicated in all patients, especially those with
- Weight loss: indicated in overweight and obese patients 
- Supportive devices (e.g., a cane or knee brace): Consider for patients with osteoarthritis of the hip and knee who are experiencing joint instability and pain when weight is placed on the joint.
- Other symptomatic therapy: e.g., acupuncture, kinesiology taping, or heat/cold therapy
- NSAIDs (e.g., ibuprofen): first-line treatment option
- Acetaminophen: an option for patients who are unable to tolerate oral NSAIDs; less effective than NSAIDs
- Opioids (e.g., tramadol): short-term use for patients who cannot tolerate or have had insufficient relief with NSAIDs
- Intraarticular glucocorticoid injection: local, short-term relief in patients with osteoarthritis of the hip and knee
- Other treatments: conditionally recommended for specific joints 
Pharmacotherapy should only be used as a short-term treatment in symptomatic patients; long-term therapy is associated with many adverse effects.
Surgical management 
Surgery is typically indicated if conservative measures fail.
- Osteotomy: realigns joints to relieve pain and potentially delay disease progression
- Indication: patients with advanced, therapy-resistant osteoarthritis of the wrist and/or ankle
- Procedure: surgical fusion of the two bones that form the joint in a functional position; can be performed arthroscopically
- Indication: patients who have experienced inadequate relief using conservative measures
- Procedure: complete or partial replacement of a joint using an endoprosthesis
- Risks: infection, blood clot (e.g., deep vein thrombosis, pulmonary embolism), dislocation, implant failure 
- See also “Treatment” in “Osteoarthritis of the hip and knee” and “Complications after osteosynthesis/arthroplasty.”