Chronic Knee Pain

What counts as chronic knee pain

Acute knee pain follows an injury or a short-lived problem and settles within weeks. Pain is called chronic when it lasts more than 3 months. About 1 in 4 adults has frequent knee pain, and the proportion rises with age. Long-term pain often comes from more than one source: worn joint surfaces, weak thigh muscles, extra body weight, and changes in how the nervous system processes pain.

Chronic knee pain symptoms

The pattern of symptoms helps narrow down the cause:

• Aching pain with walking, stairs, squatting or kneeling
• Stiffness after sitting or first thing in the morning, usually easing within 30 minutes in osteoarthritis
• Swelling, either general or a soft bulge behind the knee
• Clicking, grinding or crunching (crepitus)
• Locking or catching of the joint
• Giving way or a feeling of instability
• Reduced range of movement, difficulty fully straightening or bending the knee
• Pain at night in more advanced arthritis

Causes of chronic knee pain

Osteoarthritis

Osteoarthritis of the knee is the leading cause after age 45. The cartilage thins, the bone underneath thickens and bony spurs form. Pain is worse with use and better with rest, stiffness after rest is brief, and the knee may become bowed. Risk factors include age, excess weight, previous knee injury or surgery, and family history.

Patellofemoral pain syndrome

Patellofemoral pain syndrome causes a dull ache around or behind the kneecap. It is worse on stairs, squatting, running downhill or after sitting with the knees bent ("moviegoer's sign"). It is common in teenagers, runners and young women, and is linked to weak hip and thigh muscles.

Tendinopathy

• Patellar tendinopathy (jumper's knee) causes pain just below the kneecap with jumping and squatting.
• Quadriceps tendinopathy causes pain just above the kneecap.
• Pes anserine bursitis or tendinopathy causes pain on the inner side below the joint, common with knee arthritis and in people with diabetes.

Degenerative meniscus tears

Over time the menisci (cartilage pads) develop wear-related tears. A meniscus tear can cause pain along the joint line, swelling and catching. In middle-aged and older adults, these tears are often part of osteoarthritis and usually respond to exercise therapy rather than surgery.

Old ligament injuries

A previous ACL tear can leave the knee unstable and speeds up arthritis, even after reconstruction.

Iliotibial band syndrome

Iliotibial band syndrome causes sharp or burning pain on the outer side of the knee in runners and cyclists.

Inflammatory arthritis

Rheumatoid arthritis, psoriatic arthritis and spondyloarthritis cause warm, swollen knees with long morning stiffness, often affecting other joints. Gout and pseudogout cause recurrent attacks of severe pain and swelling.

Other causes

• A Baker's cyst behind the knee, usually from fluid produced by arthritis
• Referred pain from the hip: hip arthritis often causes pain felt in the knee
• Osteochondritis dissecans in adolescents
• Rarely, bone tumors, which cause constant pain, worse at night

Chronic knee pain by location

Diagnosis

A doctor will ask about the location, onset, triggers, swelling, locking and giving way, other painful joints and morning stiffness. They examine alignment, swelling, range of motion, ligament stability, meniscus signs and the hip.

• Osteoarthritis can be diagnosed without imaging in people over 45 with activity-related pain and less than 30 minutes of morning stiffness, according to NICE. A standing X-ray is still often used to assess severity.
• MRI is used for suspected meniscus or ligament problems, unexplained pain in younger people, or when surgery is being considered. It often shows incidental findings in older knees, so results must match the symptoms.
• Blood tests (inflammatory markers, rheumatoid factor, uric acid) help when inflammatory arthritis or gout is suspected.
• Joint aspiration removes fluid to look for crystals or infection.

Chronic knee pain treatment

Exercise therapy

Exercise is the most effective long-term treatment for almost all causes of chronic knee pain, including arthritis. A program from a physical therapist usually includes:

• Quadriceps strengthening: straight leg raises, sit-to-stand, step-ups, wall squats
• Hip strengthening: side-lying leg raises and bridges, especially for kneecap pain
• Low-impact aerobic exercise: cycling, swimming, water exercise and walking
• Balance training to reduce giving way

Benefits build over 6 to 12 weeks and last as long as you keep exercising. Some soreness during exercise is acceptable if it settles within 24 hours.

Weight management

Each 1 lb (0.45 kg) of body weight adds roughly 4 lb (1.8 kg) of load across the knee when walking. Losing 5 to 10% of body weight meaningfully reduces knee arthritis pain.

Medicines

• Topical NSAIDs such as diclofenac gel are recommended first for knee osteoarthritis, with fewer side effects than tablets.
• Oral NSAIDs such as ibuprofen or naproxen at the lowest effective dose for the shortest time. Avoid them with stomach ulcers, kidney disease, heart failure or blood thinners.
• Acetaminophen (paracetamol) has only a small effect on osteoarthritis pain but may help some people.
• Duloxetine may be prescribed when pain persists.
• Opioids are not recommended for long-term knee pain because of risks and limited benefit.

Injections

• Corticosteroid injections give short-term relief, typically for a few weeks, during flares.
• Hyaluronic acid and platelet-rich plasma injections have inconsistent evidence, and major guidelines do not routinely recommend them.

Supports and aids

Supportive footwear, a cane held in the opposite hand, knee braces for unloading one side of the joint, and kinesiology taping for kneecap pain can help.

Surgery

• Arthroscopic "clean-out" surgery is not recommended for knee osteoarthritis or degenerative meniscus tears, because trials show no lasting benefit over exercise.
• Partial or total knee replacement is very effective for severe osteoarthritis when pain and disability persist despite non-surgical treatment.
• Realignment surgery (osteotomy) may suit younger, active people with arthritis on one side of the knee.

Complications

Untreated chronic knee pain leads to reduced activity, muscle weakness, weight gain, falls, poor sleep and low mood, which in turn worsen pain. Breaking this cycle with exercise is central to treatment.

Prevention

• Keep thigh and hip muscles strong.
• Maintain a healthy weight.
• Build up running or sports training gradually.
• Get knee injuries properly rehabilitated before returning to sport.

Frequently asked questions

What is the most common cause of chronic knee pain?

In adults over 45, osteoarthritis is the most common cause. In teenagers and younger adults, patellofemoral (kneecap) pain is more common. Tendinopathy, old meniscus or ligament injuries, and inflammatory arthritis account for many other cases.

What are the symptoms of chronic knee pain?

Typical symptoms include aching with walking or stairs, stiffness after rest, swelling, grinding or clicking, reduced movement and sometimes locking or giving way. The pattern and location of the pain help identify the cause.

What is the best treatment for chronic knee pain?

Strengthening exercise is the most effective long-term treatment, especially for the thigh and hip muscles. Weight loss, topical or oral NSAIDs and supportive aids help. Knee replacement is an option for severe arthritis that has not responded to these measures.

Should I rest a chronically painful knee?

Complete rest usually makes chronic knee pain worse, because muscles weaken and the joint stiffens. Stay active with low-impact exercise, reduce activities that clearly flare pain, and build up gradually with a physical therapist's guidance.

When does chronic knee pain need surgery?

Surgery is considered when severe pain and disability continue despite several months of exercise, weight management and medicines, and imaging confirms significant arthritis. Knee replacement gives good relief for most people. Keyhole clean-outs are not recommended for arthritis.