Knee osteoarthritis

By The Treatment Registry editors

Degenerative joint disease of the knee, characterised by progressive cartilage loss, joint-space narrowing, and pain. The treatment ladder runs from lifestyle and medical management through intra-articular injections, joint-preserving surgery, and finally joint replacement. Modern guidelines have substantially reduced the role of arthroscopy in osteoarthritis without mechanical symptoms.

Clinical overview

Signs and symptoms

The knee is one of the large weight-bearing joints most commonly affected by osteoarthritis, and the main symptom is pain, causing loss of ability and often stiffness. The pain is typically made worse by prolonged activity and relieved by rest, while stiffness is most common in the morning, usually lasting less than thirty minutes but returning after periods of inactivity such as prolonged sitting. Pain when ascending or descending stairs, or getting in and out of a car or bath, is associated with osteoarthritis of the patellofemoral joint behind the kneecap, which is stressed with knee flexion. The knee may produce a crackling noise, called crepitus, when moved, and patients may report joint locking and instability. Symptoms usually progress slowly over years and, as the disease advances, gait is typically affected.

Causes and risk factors

Damage from mechanical stress with insufficient self-repair by the joint is believed to be the primary cause. Contributing sources of stress include bony misalignment, mechanical injury, excess body weight, loss of strength in the muscles supporting the knee, and impaired peripheral nerves. Risk increases with ageing, a history of joint injury, and family history, and osteoarthritis of the knees is twice as common in those with obesity. It is more prevalent among post-menopausal women, who also tend to have more severe symptoms and imaging findings than men. Occupational risk for knee osteoarthritis is raised in those who kneel or squat, who combine heavy lifting with a kneeling or squatting posture, and who work standing up. Diabetes doubles the risk of a joint replacement due to osteoarthritis. Underlying this, cartilage is progressively lost, osteophytes form at the joint margins, and the synovium becomes inflamed.

How it is diagnosed

Diagnosis is made with reasonable certainty based on history and clinical examination, and X-rays may confirm it. Typical radiographic changes include joint-space narrowing, subchondral sclerosis, subchondral cyst formation, and osteophytes. The combination of knee pain and osteophytes on X-ray has good sensitivity and specificity for the diagnosis. X-rays may not correlate with physical examination findings or the degree of pain, especially early in the disease when imaging can appear relatively normal. The Kellgren-Lawrence scale, using projectional radiography, is used to grade knee osteoarthritis, and the WOMAC scale accounts for pain, stiffness, and functional limitation.

Who it affects

Globally, as of 2010, approximately 250 million people had osteoarthritis of the knee, about 3.6% of the world's population. Together, knee and hip osteoarthritis ranked 11th for disability globally among 291 disease conditions assessed. Osteoarthritis overall is the most common form of arthritis, affecting about 237 million people or 3.3% of the world's population as of 2015, and it becomes more common as people age.

Clinical overview sourced from encyclopaedic medical reference; see sources below. General information only — not a substitute for individual clinical assessment.

Treatment ladder

Conservative options are first-line where appropriate; surgical options are typically reserved for cases where lower-tier options are unsuitable or have failed. Decisions are individual and depend on clinical assessment.

Conservative

Weight management and physiotherapy
First-line for all symptomatic patients. Each kilogram lost reduces knee load substantially during walking; supervised exercise improves pain and function.
Analgesia (paracetamol, NSAIDs)
Topical NSAIDs preferred for localised pain; systemic NSAIDs effective but with cardiovascular and gastrointestinal risk profiles to consider in older patients.

Procedural

Intra-articular corticosteroid injection
Short-term symptomatic relief (weeks to months). Repeated injections over time are associated with cartilage loss and are not a long-term solution.
Hyaluronic acid (viscosupplementation) injection
Limited and contested evidence; some patients report symptomatic improvement.
Knee arthroscopy
Now of limited evidence in osteoarthritis without mechanical locking; current AAOS and NICE guidance has substantially reduced its routine indication.

Surgical

Unicompartmental knee replacement
Partial replacement when osteoarthritis is confined to one compartment. Faster recovery and better range of motion than total replacement, but with higher revision rates in some series.
Total knee replacement · View procedure page
Definitive surgical treatment for end-stage osteoarthritis. Modern implant survivorship at 15-20 years exceeds 90% in registry data.
High tibial osteotomy
Realignment osteotomy to redistribute load away from the affected compartment. Selected younger active patients with isolated medial-compartment disease.

Related procedures

Total Knee Replacement

Sources

[1]AAOS — Surgical Management of Osteoarthritis of the Knee Clinical Practice Guideline — aaos.org(accessed 2026-05-09)
[2]Wikipedia — Osteoarthritis — en.wikipedia.org(accessed 2026-07-24)
[3]National Joint Registry for England, Wales, Northern Ireland and the Isle of Man — Annual Report — njrcentre.org.uk(accessed 2026-05-09)

Sources marked “on file” are held by The Treatment Registry but are not publicly accessible.