Knee Osteoarthritis
Overview
Knee osteoarthritis affects the whole joint and can cause pain, stiffness, swelling and reduced function. Symptoms often fluctuate and do not always match X-ray severity. A clinical assessment is usually more important than a scan at the start of care. Education, exercise and support for self-management are central. Knee replacement may be considered when symptoms remain unacceptable despite appropriate non-surgical treatment.
What is knee osteoarthritis?
The knee has three main compartments: the inner, outer and kneecap compartments. Osteoarthritis may affect one area or several. Joint changes can include cartilage loss, altered bone, inflammation, meniscal degeneration, stiffness and muscle weakness.
Age is one risk factor, but osteoarthritis is not simply ‘wear and tear’. Previous injury, joint alignment, genetics, inflammatory disease and the loads placed on the knee can contribute. Higher body weight can increase joint load for some people, but it is not the sole explanation for pain. Symptoms often fluctuate, and a flare does not necessarily mean that new damage has occurred.
Common symptoms
- Pain with walking, stairs, standing from a chair, kneeling or prolonged activity.
- Stiffness after rest, reduced bend or difficulty fully straightening the knee.
- Swelling, clicking, grinding or a feeling of reduced confidence in the leg.
- Reduced walking distance, sleep disturbance or difficulty with work and recreation.
- Change in leg alignment in more advanced disease.
Assessment and imaging
Assessment considers the pattern of pain, swelling, mechanical symptoms, previous injury, work and activity goals, general health and the effect on daily life. Examination includes gait, alignment, movement, stability, strength and the hip and back where relevant.
Typical knee osteoarthritis can usually be diagnosed from the history and examination without routine imaging. When imaging is needed, weight-bearing X-rays are generally the first test—for example, when symptoms are atypical, another diagnosis is possible or surgery is being considered. MRI is not a routine test for knee osteoarthritis. Age-related meniscal tears are common on MRI and may not be the main pain source.
Non-surgical treatment
- Clear information, pacing and adjustment of aggravating activities while continuing useful movement and participation where possible.
- A tailored strengthening and aerobic exercise program. Exercise does not damage an osteoarthritic knee, although the dose may need adjustment if pain or swelling flares.
- Support with weight management when it is relevant to your health and goals, without making weight the sole explanation for pain.
- A walking stick, brace or other aid when it improves comfort, balance or confidence.
- Attention to sleep, mood and other health conditions when they are affecting pain or the ability to stay active.
- A topical anti-inflammatory medicine is often considered first. Oral anti-inflammatory medicine may be suitable for some people after checking stomach, kidney, heart, bleeding and medication risks.
- A corticosteroid (cortisone) injection may provide short-term relief for some people, which can help participation in exercise. It does not restore cartilage, and the value and risk of repeat injections should be reviewed individually.
- Hyaluronic acid injections are not routinely recommended for knee osteoarthritis because consistent meaningful benefit has not been established.
What usually does not help?
Arthroscopic ‘clean-out’ surgery does not improve uncomplicated knee osteoarthritis. Arthroscopy may still have a role for a separate problem such as a displaced traumatic meniscal tear, loose body or another specific mechanical lesion, but this requires individual assessment.
Complete rest and passive treatments alone do not rebuild strength or function. Long-term opioid medicines are generally avoided because benefit is limited and harms can accumulate. Each treatment should have a clear goal and be reviewed if it is not helping.
When may surgery be considered?
Knee replacement may be discussed when pain, stiffness or deformity has a substantial effect on quality of life and a reasonable trial of non-surgical care has not provided acceptable control. Total replacement is used when disease is widespread. Partial replacement may suit a smaller group with disease confined to one compartment.
The decision is based on symptoms, examination, appropriate imaging, health, expectations and surgical risk—not age, body weight or an X-ray in isolation. Referral should not be withheld solely because of age, disability or body mass index.
When to seek prompt review
- A hot, markedly swollen knee with fever or feeling generally unwell.
- Inability to bear weight after a fall or injury.
- A truly locked knee that cannot be straightened after an acute injury.
- Rapidly increasing swelling, unexplained night pain or new calf swelling.
- New weakness or numbness in the leg.
Frequently asked questions
Does bone-on-bone arthritis always require surgery?
No. Imaging is only one part of the decision. Surgery is considered when symptoms and loss of function remain unacceptable despite appropriate non-surgical care.
Will exercise make the arthritis worse?
Appropriate exercise is generally safe and is a core treatment. The type and dose may need to be adjusted during a flare.
Do I need an MRI before seeing a surgeon?
Usually not when weight-bearing X-rays and examination are sufficient. MRI may be useful when another diagnosis is suspected.
Can arthroscopy wash out arthritis?
Arthroscopy is not recommended for uncomplicated degenerative knee osteoarthritis. It does not reverse the underlying joint disease.
General information
This page provides general information only. It cannot diagnose your condition or replace advice from a clinician who has assessed you. Your treatment and recovery plan may differ from the examples described here. Follow the instructions from your treating team. In an emergency, call 000 or attend the nearest emergency department.