Overview

Knee osteoarthritis is a common joint condition that usually develops gradually from middle age onward. The cartilage that covers the ends of the bones thins and roughens, the bone underneath changes, and the joint may become painful, stiff and at times swollen.

"Wear and tear" is a common shorthand, but it is incomplete. Osteoarthritis is an active process involving the whole joint — cartilage, bone, the joint lining and the muscles around it — and it does not behave like a machine wearing out. How much pain someone feels does not track neatly with how the knee looks on a scan.

Typical Pattern

Pain that is worse with activity such as walking, stairs or squatting, and eases with rest
Stiffness after sitting or first thing in the morning that usually eases within minutes
Grinding or grating sensations; painless clicks are common and not alarming by themselves
Flare-ups: periods when pain and swelling increase, then settle
Symptoms that vary from week to week, sometimes with little change in activity

Why It Develops

Age is the strongest risk factor, and the condition becomes more common with each decade. A previous knee injury — especially a ligament or meniscus tear — higher body weight, muscle weakness, family history and some occupations or sports with heavy knee loading all increase the chance of developing it.

Imaging is a poor predictor of symptoms. In a meta-analysis of adults with no knee pain at all, MRI showed features of osteoarthritis (cartilage, bone-spur or meniscal changes) in 4% to 14% of people under 40 and in 19% to 43% of people 40 and older. Seeing changes on a scan is not the same as knowing how a knee feels.

Treatment

Current guidelines agree: education, exercise and, when relevant, weight management are the core treatments. That usually means:

Learning about the condition and what to expect, including that flare-ups are normal
Regular land-based exercise: strengthening the quadriceps and hip muscles plus aerobic activity such as walking or cycling
Choosing versions of exercise you can tolerate; mild discomfort during activity is normal, while sharp pain or lasting flare-ups are a signal to adjust
Managing body weight if you are overweight, because weight directly affects knee loading
Topical anti-inflammatory creams or gels can help for short periods; oral pain medication is used at the lowest effective dose for the shortest time to support exercise, according to current guidelines
Injections and surgery are not first-line; joint replacement is considered only when symptoms and function are not controlled with conservative care

Muscles around an osteoarthritic knee are usually weaker, and strengthening them is one of the most effective things you can do. Resting too much tends to make pain harder to manage over time. Activity is not the enemy.

When to Get Assessed

Most knee osteoarthritis is managed in primary care, and a supervised exercise program is often enough to start. Arrange an assessment if pain is persistent, worsening or limiting daily life, or if you are unsure something else is going on. Seek prompt care for a hot, red, swollen knee with fever, sudden severe swelling after an injury, a locked knee, inability to bear weight, or symptoms that worsen rapidly over days or weeks.

References

Bannuru RR, et al. "OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis." Osteoarthritis and Cartilage. 2019;27(11):1578-1589. https://pubmed.ncbi.nlm.nih.gov/31278997/
National Institute for Health and Care Excellence. "Osteoarthritis in over 16s: diagnosis and management." NICE guideline NG226. 2022. https://www.nice.org.uk/guidance/ng226
Culvenor AG, et al. "Prevalence of knee osteoarthritis features on magnetic resonance imaging in asymptomatic uninjured adults: a systematic review and meta-analysis." British Journal of Sports Medicine. 2019;53(20):1268-1278. https://pubmed.ncbi.nlm.nih.gov/29886437/

This information is for education only and is not a medical diagnosis. InjuryAtlas does not replace an assessment by a qualified health professional. If you have severe pain, visible deformity, numbness, loss of function, or symptoms that are getting worse, seek medical care promptly.

Knee Osteoarthritis