Knee Arthritis

How the knee is affected

The knee joint is where the thighbone (femur), shinbone (tibia) and kneecap (patella) meet. Smooth cartilage covers the bone ends, and two C-shaped menisci cushion the joint. In arthritis:

• cartilage thins and roughens
• the bone underneath thickens and forms bone spurs (osteophytes)
• the joint lining becomes inflamed and produces extra fluid, causing swelling
• in advanced disease, cartilage wears away so bone rubs on bone

Types of knee arthritis

Patellofemoral arthritis affects the joint behind the kneecap and causes pain with stairs, squatting and getting up from chairs.

Symptoms

• pain, worse with walking, stairs, kneeling or standing up, easing with rest at first
• stiffness, especially in the morning or after sitting, usually lasting under 30 minutes in osteoarthritis
• swelling and warmth
• creaking, grinding or crackling (crepitus)
• reduced range of motion; difficulty fully bending or straightening
• the knee buckling or feeling weak
• deformity: bowlegs or knock-knees in advanced disease
• night pain in severe arthritis

A swelling behind the knee may be a Baker's cyst, which often accompanies arthritis.

Risk factors

• age
• excess body weight: each extra pound adds several pounds of force across the knee when walking
• previous knee injury or surgery
• female sex
• genetics and family history
• jobs with frequent kneeling, squatting and heavy lifting
• leg alignment differences
• weak thigh muscles

Diagnosis

• history and examination: swelling, tenderness, range of motion, alignment, stability
• X-rays, ideally standing: show joint space narrowing, bone spurs and alignment. Changes on X-ray do not always match how much pain you have
• blood tests if inflammatory arthritis is suspected: CRP, ESR, rheumatoid factor, anti-CCP, uric acid
• joint fluid aspiration to look for infection or crystals
• MRI is rarely needed for typical osteoarthritis

Treatment

Exercise and physical therapy

Exercise is the most effective treatment for knee osteoarthritis and is strongly recommended by the ACR and AAOS:

• strengthening the quadriceps, hamstrings and hip muscles
• low-impact aerobic activity: walking, cycling, swimming, water aerobics
• flexibility and balance exercises
• tai chi and yoga

Start gently and build up. Some discomfort during exercise is normal and does not mean you are damaging the joint.

Weight loss

Losing 5% to 10% of body weight can noticeably reduce knee pain and improve function in people who are overweight.

Medicines

• topical NSAIDs (diclofenac gel): first choice for knee osteoarthritis, with few side effects
• oral NSAIDs (ibuprofen, naproxen): effective but with stomach, kidney and heart risks; use at the lowest effective dose, following the label
• acetaminophen (paracetamol): modest benefit for some
• duloxetine for chronic pain in some people
• corticosteroid injections: short-term relief for flares, typically limited to a few a year
• hyaluronic acid injections: benefit is uncertain, and major guidelines do not routinely recommend them
• disease-modifying drugs for rheumatoid arthritis and urate-lowering therapy for gout

Glucosamine, chondroitin and platelet-rich plasma (PRP) are not recommended by major US guidelines because of inconsistent evidence.

Aids and supports

• a cane in the hand opposite the painful knee
• knee braces for alignment or kneecap support
• supportive, cushioned shoes

Surgery

• total knee replacement: replaces the worn surfaces with metal and plastic. Highly effective for severe arthritis when non-surgical treatments no longer help. Most people have much less pain and better function, and modern implants often last 20 years or more
• partial knee replacement when only one compartment is worn
• osteotomy: realigning the bone to shift weight off the damaged part, for younger, active people
• arthroscopic "clean-out" is not recommended for knee osteoarthritis because it does not improve outcomes

Living with knee arthritis

• stay active and pace activities
• use heat for stiffness and ice for flares
• set up your home to reduce strain: rails on stairs, higher chairs
• keep moving even on bad days, with gentler exercise

Frequently asked questions

What are the first signs of knee arthritis?

Early signs include knee pain after activity, stiffness in the morning or after sitting that eases within half an hour, mild swelling and creaking. Over time, pain may occur with less activity and limit walking or stairs.

What is the best treatment for knee arthritis?

Exercise and weight loss are the most effective first treatments, supported by physical therapy, topical NSAIDs, and other pain relief. Steroid injections help flares. Knee replacement is very effective when severe arthritis no longer responds.

What exercises are good for knee arthritis?

Quadriceps and hip strengthening, straight leg raises, mini squats, step-ups, cycling, walking, swimming and water exercise are all helpful. A physical therapist can design a program suited to your knee.

When should I consider knee replacement?

Consider it when pain and stiffness significantly limit daily activities or sleep, and when exercise, weight loss, medicines and injections no longer give adequate relief. X-rays showing severe joint damage support the decision.

Does walking make knee arthritis worse?

No. Regular walking strengthens muscles, maintains joint movement and usually reduces pain over time. Pace yourself, wear supportive shoes and use a cane if needed.