Osteoarthritis of the Knee

What happens in knee osteoarthritis

The knee has three compartments: inner (medial), outer (lateral) and behind the kneecap (patellofemoral). Each is lined with smooth cartilage that lets the bones glide. In osteoarthritis:

• cartilage becomes thinner and rougher
• the bone underneath thickens and forms bony spurs (osteophytes)
• the joint lining becomes inflamed and may produce extra fluid
• surrounding muscles weaken and ligaments may loosen

It is not simply "wear and tear": it is an active process of damage and repair involving the whole joint. The inner compartment is most often affected, which can cause a bow-legged appearance.

Symptoms

• Pain: usually gradual, worse with walking, stairs, kneeling or getting up from a chair, and eased by rest. In advanced disease, pain may occur at rest and at night.
• Stiffness: after sitting or first thing in the morning, typically lasting less than 30 minutes. See knee stiffness.
• Swelling: soft swelling from fluid, sometimes with a Baker's cyst behind the knee.
• Creaking or grinding (crepitus) when moving.
• Reduced movement: difficulty fully bending or straightening.
• Instability or giving way, often from weak thigh muscles.
• Deformity: bow legs or knock knees in advanced disease.

Symptoms often fluctuate, with flares lasting days to weeks.

Risk factors

• Age: most common after 50
• Excess weight: increases load on the knee and inflammation. Each pound of weight loss reduces knee load substantially with each step
• Previous knee injury: meniscus tears, ACL injuries and fractures raise the risk years later
• Female sex
• Family history
• Occupations involving heavy lifting, kneeling and squatting
• Leg alignment problems and muscle weakness

Diagnosis

Knee osteoarthritis can be diagnosed clinically in people aged 45 or older with activity-related knee pain and morning stiffness lasting no more than 30 minutes. Examination looks for swelling, crepitus, bony enlargement, tenderness, range of movement and alignment.

• X-rays taken standing show joint space narrowing, bone spurs and bone changes, and help plan surgery. X-ray findings do not always match symptoms.
• Blood tests are not needed for diagnosis but may be used to exclude rheumatoid arthritis or gout.
• Joint aspiration if infection or crystals are suspected.
• MRI is rarely needed unless another problem is suspected.

Stages

Doctors often grade X-ray severity using the Kellgren-Lawrence scale:

Treatment decisions are based on symptoms and function, not X-ray grade alone.

Treatment

Core treatments for everyone

• Exercise: the most effective treatment. Strengthening the thigh and hip muscles, plus aerobic activity such as walking, cycling, swimming and water exercise, reduces pain and improves function. Tai chi also has good evidence. Physical therapy helps design a program.
• Weight loss: losing 5 to 10 percent of body weight can noticeably reduce pain in people who are overweight.
• Education and self-management: pacing activities, staying active, and understanding that exercise does not damage the joint.

Pain relief

• Topical NSAIDs (such as diclofenac gel): recommended as a first choice, with fewer side effects than tablets. Follow the label.
• Oral NSAIDs (ibuprofen, naproxen): effective for flares. Use the lowest effective dose for the shortest time. Avoid with stomach ulcers, kidney disease, some heart conditions or blood thinners.
• Acetaminophen (paracetamol): modest benefit at best.
• Duloxetine: for some people with persistent pain.
• Opioids are generally not recommended because of limited benefit and significant risks.

Injections

• Corticosteroid injections: short-term relief, typically for weeks, useful during flares.
• Hyaluronic acid and platelet-rich plasma (PRP) injections: evidence is inconsistent, and major US rheumatology guidelines advise against routine use.

Supports and devices

• A cane in the hand opposite the painful knee
• Knee braces for alignment problems or kneecap pain
• Supportive, cushioned footwear

Treatments not recommended

Glucosamine and chondroitin supplements have not shown consistent benefit for knee osteoarthritis. Arthroscopic "clean-out" surgery (washout and debridement) does not help typical knee osteoarthritis.

Surgery

• Total knee replacement: replaces the joint surfaces with metal and plastic components. It is very effective for severe pain and disability despite other treatments. Most implants last 20 years or more.
• Partial (unicompartmental) knee replacement: when only one compartment is affected.
• Osteotomy: cutting and realigning the bone to shift load, for younger, active people with arthritis in one compartment.

Outlook

Knee osteoarthritis usually progresses slowly, and many people have stable symptoms for years. Regular exercise, weight management and good pain control keep most people active. Those with severe disease often do very well after knee replacement.

Frequently asked questions

What are the first signs of knee osteoarthritis?

Early signs include knee pain during or after activity such as walking or climbing stairs, brief stiffness after sitting or on waking, and creaking or grinding. Mild swelling may come and go. Symptoms usually develop gradually over months to years.

What is the best treatment for knee osteoarthritis?

Exercise, especially strengthening the thigh and hip muscles combined with aerobic activity, is the most effective treatment, along with weight loss if needed. Topical NSAIDs help pain. Steroid injections help flares, and knee replacement is very effective for severe symptoms.

Can knee osteoarthritis be reversed?

Cartilage loss cannot be reversed, but symptoms can improve substantially. Many people have less pain and better function with exercise, weight loss and pain relief. Progression is often slow, and some people stay stable for many years.

Is walking good for knee osteoarthritis?

Yes. Walking is safe and helpful for most people with knee osteoarthritis. It strengthens muscles, supports weight loss and reduces pain over time. Start with short walks, build up gradually, wear supportive shoes and use a cane if needed.

When should I consider knee replacement?

Consider knee replacement when severe pain, stiffness or instability limit daily activities and sleep despite trying exercise, weight loss, medicines and injections, and X-rays show advanced arthritis. An orthopedic surgeon can discuss the benefits, risks and recovery.