Knee Pain: Symptoms, Causes, and When to Get Help

Knee pain is one of the most common musculoskeletal complaints, affecting people of all ages — from teenagers dealing with sports injuries to older adults managing arthritis. Understanding what is causing your knee pain is the first step toward finding effective relief.

Common Causes of Knee Pain

The knee is a complex joint that bears the full weight of the body with every step. It is held together by ligaments, cushioned by cartilage and fluid-filled sacs, and powered by large muscle groups. Any of these structures can be a source of pain.

Osteoarthritis

The most common cause of knee pain in adults over 40, osteoarthritis occurs when the cartilage that cushions the knee joint gradually breaks down. This leads to bone-on-bone contact, causing pain, stiffness, swelling, and reduced range of motion. Symptoms often worsen with activity and improve briefly with rest before stiffening again.

Meniscus Tears

The menisci are two C-shaped pieces of cartilage that act as shock absorbers between the thighbone and shinbone. They can tear during twisting movements, sudden pivots, or simply from age-related degeneration. A torn meniscus typically causes pain along the inner or outer knee, swelling, and a sensation of the knee catching or locking.

Ligament Injuries (ACL and MCL)

The anterior cruciate ligament (ACL) and medial collateral ligament (MCL) are two of the most commonly injured knee ligaments. ACL tears often occur with a sudden direction change or landing from a jump, frequently accompanied by a loud pop and rapid swelling. MCL sprains typically result from a direct blow to the outer knee and cause pain along the inner side of the joint.

Patellofemoral Syndrome

Also called runner’s knee, patellofemoral syndrome involves pain around or behind the kneecap. It develops when the patella does not track smoothly in its groove, creating friction and irritation. It is especially common in runners, cyclists, and people who spend long periods sitting with bent knees.

Tendinitis

Patellar tendinitis (jumper’s knee) involves inflammation of the tendon connecting the kneecap to the shinbone. It causes pain just below the kneecap that worsens with jumping, running, or climbing stairs. Quadriceps tendinitis produces similar pain above the kneecap.

Bursitis

Bursae are small fluid-filled sacs that reduce friction around the knee joint. Repeated kneeling, overuse, or direct trauma can inflame these sacs, causing swelling and tenderness directly over the kneecap or along the inner side of the knee.

Gout

Although gout most commonly affects the big toe, it can occur in the knee. Gout attacks cause sudden, severe pain, redness, warmth, and swelling due to uric acid crystals depositing in the joint. Episodes typically develop quickly and can last days to weeks without treatment.

Knee Pain by Age Group

While any condition can occur at any age, certain causes of knee pain are more common at different life stages.

Under 30: Sports Injuries and Overuse

Younger adults and adolescents most commonly experience knee pain from sports-related injuries and repetitive stress. ACL and MCL tears, meniscus injuries from contact sports, patellar tendinitis from jumping sports, and patellofemoral syndrome from running are all frequent in this age group. Osgood-Schlatter disease — a painful lump below the kneecap — is especially common in active teenagers during growth spurts.

Ages 30–50: Early Arthritis and Tendinitis

In middle adulthood, overuse injuries remain common, and early signs of osteoarthritis may begin to appear, particularly in people with prior knee injuries or excess body weight. Meniscal degeneration can occur even without a specific injury. Tendinitis and bursitis frequently affect people in physically demanding occupations or those who have recently increased their activity level.

Over 50: Osteoarthritis and Degenerative Changes

Osteoarthritis is the dominant cause of knee pain after age 50. Cartilage loss, joint space narrowing, and bone spur formation lead to progressive pain, stiffness, and reduced mobility. Meniscus degeneration is nearly universal in this age group and often occurs alongside arthritis. Gout and pseudogout also become more prevalent with age.

Warning Signs That Need Attention

Some knee symptoms require prompt medical evaluation. Do not delay seeing a provider if you experience any of the following:

• Locked knee: The knee becomes stuck in a bent position and cannot be fully straightened — often caused by a displaced meniscus tear or loose body in the joint
• Giving way: The knee buckles or collapses under your weight, suggesting ligament instability or significant quadriceps weakness
• Significant swelling: Rapid swelling after an injury (within hours) often indicates bleeding inside the joint and warrants same-day evaluation
• Inability to bear weight: If you cannot stand or walk on the affected leg, a fracture or severe ligament injury should be ruled out
• Visible deformity: Any obvious change in the shape or alignment of the knee requires immediate evaluation
• Fever with joint swelling: Warmth, redness, swelling, and fever together may indicate septic arthritis, a serious joint infection requiring urgent treatment

When to See a Specialist

Not every episode of knee pain requires a specialist visit, but certain patterns suggest that a pain management physician or orthopedic specialist should be involved:

• Pain that has persisted for more than two weeks without improvement
• Knee pain that limits your ability to walk, climb stairs, or perform daily activities
• Swelling around the knee that does not resolve with rest and ice within a few days
• Popping, clicking, or catching sensations accompanied by pain
• Recurrent episodes of pain that keep coming back after activity
• Pain severe enough to disrupt sleep

A specialist can perform a thorough examination, review imaging studies, and develop a targeted treatment plan rather than relying on generic rest-and-ice advice alone.

Treatment Options

Knee pain treatment depends on the underlying cause, severity, and your individual goals. Modern pain management offers a range of effective options beyond surgery:

• Physical therapy: Strengthening the muscles around the knee — particularly the quadriceps, hamstrings, and hip abductors — is foundational to knee pain recovery and prevention
• Injection therapies: Corticosteroid injections reduce inflammation, while hyaluronic acid injections lubricate the joint in osteoarthritis. Targeted injections are often effective when oral medications fall short.
• Regenerative medicine: PRP (platelet-rich plasma) therapy and prolotherapy may help stimulate tissue repair in conditions like tendinitis, partial ligament tears, and early arthritis.
• Bracing and orthotics: Offloading braces can reduce pain in unicompartmental arthritis; custom orthotics may correct alignment issues contributing to patellofemoral pain
• Medications: Anti-inflammatory medications, topical agents, and other pain-modulating treatments can be part of a comprehensive plan

See our full treatment options guide for a complete overview of available approaches.

Assess Your Knee Pain

Not sure what is causing your knee pain or where to start? Our free consultation tool walks you through your symptoms and connects you with the right type of specialist for your situation.

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Find a Knee Pain Specialist Near You

Ready to get a professional evaluation? Use our clinic directory to find board-certified pain management specialists near you who treat knee pain. With over 5,000 clinics listed across all 50 states, you can search by location, read patient reviews, and compare providers.

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