What Causes Knee Pain and When Should You See a Doctor?

What Should You Do First for Knee Pain?

Begin with the RICE protocol: rest from aggravating activities, apply ice for 15 to 20 minutes every 2 to 3 hours, use compression with an elastic bandage, and elevate the knee above heart level. Take over-the-counter NSAIDs like ibuprofen for pain and inflammation. If pain persists beyond 2 weeks, seek medical evaluation.

The RICE protocol (Rest, Ice, Compression, Elevation) remains the standard initial treatment for most acute knee pain. Rest does not mean complete immobilization but rather avoiding the specific activity that provoked the pain. Ice application reduces blood flow to the area, limiting inflammation and providing analgesic effects. Apply a cold pack wrapped in a thin towel for 15 to 20 minutes every 2 to 3 hours during the first 48 to 72 hours. Compression with an elastic bandage or knee sleeve helps control swelling, and elevation above the heart assists venous return.

Over-the-counter NSAIDs including ibuprofen (400 to 600 mg every 6 to 8 hours) and naproxen (220 to 440 mg every 8 to 12 hours) are effective first-line medications for knee pain. Topical NSAIDs such as diclofenac gel (Voltaren) are recommended by the American College of Rheumatology (ACR) as a first-line treatment for knee osteoarthritis, offering local pain relief with fewer systemic side effects. Apply topical diclofenac 4 times daily to the affected knee as directed.

Early activity modification is important but does not mean stopping all movement. Continue low-impact activities that do not worsen your pain, such as swimming, cycling on a stationary bike with low resistance, or walking on flat surfaces. Maintaining some level of activity preserves quadriceps strength, which is critical for knee joint stability. If you cannot bear weight on the knee, experience significant swelling within 2 hours of an injury, or hear a popping sound at the time of injury, seek prompt medical evaluation.

Topical NSAIDs such as diclofenac gel are recommended by the ACR as first-line treatment for knee osteoarthritis[1]

What Are the Most Common Causes of Knee Pain?

The most common causes of knee pain vary by age and activity level. In younger active individuals, patellofemoral pain syndrome, patellar tendinopathy, and ligament injuries predominate. In adults over 50, osteoarthritis is the leading cause. Meniscus tears affect all age groups. Understanding the pain location and pattern helps identify the likely cause.

Patellofemoral pain syndrome (PFPS), commonly called runner's knee, is the most frequent cause of anterior knee pain, particularly in women and young adults. It causes diffuse pain around or behind the kneecap that worsens with squatting, stair climbing, prolonged sitting, and running. The condition results from abnormal tracking of the patella in the trochlear groove, often due to quadriceps weakness (especially the vastus medialis oblique), tight lateral structures, and hip abductor weakness that allows excessive knee valgus during weight-bearing activities.

Osteoarthritis (OA) of the knee is the most common form of arthritis, affecting over 32.5 million adults in the United States according to the CDC. It involves progressive degeneration of the articular cartilage covering the ends of the femur and tibia, along with bony changes, synovial inflammation, and meniscal degeneration. Risk factors include age over 50, female sex, obesity, previous knee injury, and genetics. Symptoms include pain that worsens with activity, morning stiffness lasting less than 30 minutes, crepitus (grinding sensation), and gradually decreasing range of motion.

Meniscus tears are among the most common knee injuries, occurring both from acute traumatic twisting injuries in younger athletes and from degenerative changes in older adults. The medial meniscus is torn more frequently than the lateral. Symptoms include pain along the joint line, swelling, catching or locking, and difficulty fully straightening the knee. Not all meniscus tears require surgery, as research published in the New England Journal of Medicine has shown that physical therapy is as effective as arthroscopic partial meniscectomy for degenerative meniscal tears in middle-aged and older adults.

Ligament injuries, including anterior cruciate ligament (ACL) tears, medial collateral ligament (MCL) sprains, and posterior cruciate ligament (PCL) injuries, typically result from sports-related trauma. ACL tears often involve a noncontact pivoting mechanism with an audible pop and rapid swelling within 2 to 4 hours. Other causes of knee pain include patellar tendinopathy (jumper's knee), iliotibial band syndrome, pes anserine bursitis, and referred pain from the hip or lumbar spine.

Physical therapy is as effective as arthroscopic partial meniscectomy for degenerative meniscal tears[2]

How Is Knee Pain Diagnosed?

Knee pain is primarily diagnosed through a thorough clinical history and physical examination. Your doctor will assess the pain location, onset, aggravating factors, and perform specific tests including the Lachman test for ACL integrity and McMurray test for meniscus tears. Imaging is ordered selectively based on clinical findings, not routinely for all knee pain.

A comprehensive clinical history is the most important diagnostic tool for knee pain. Your healthcare provider will ask about the onset (sudden versus gradual), location (anterior, medial, lateral, posterior), aggravating activities (stairs, running, squatting), mechanical symptoms (locking, catching, giving way), and any history of trauma. The pattern of symptoms often narrows the differential diagnosis significantly before any imaging is obtained. For example, anterior pain that worsens with prolonged sitting and stair descent strongly suggests patellofemoral pain syndrome.

Physical examination includes inspection for swelling, malalignment, and muscle atrophy, palpation of specific structures along the joint line and around the patella, range of motion assessment, and special tests. The Lachman test and anterior drawer test evaluate ACL integrity, the McMurray test assesses the menisci, and varus and valgus stress tests evaluate the collateral ligaments. The patellar grind test and Clarke sign help diagnose patellofemoral conditions. A thorough examiner can accurately diagnose most knee conditions without imaging.

Imaging is indicated when clinical examination suggests a structural injury or when symptoms do not respond to initial conservative treatment. Weight-bearing X-rays are the first-line imaging study for suspected osteoarthritis, revealing joint space narrowing, osteophytes, and subchondral sclerosis. MRI is the gold standard for evaluating soft tissue injuries including meniscus tears, ligament injuries, and cartilage damage. The Ottawa knee rules provide evidence-based criteria for when X-rays are needed after acute knee trauma, reducing unnecessary imaging by up to 30%.

The Ottawa knee rules provide evidence-based criteria that reduce unnecessary imaging by up to 30%[3]

What Exercises Help Relieve Knee Pain?

Quadriceps strengthening is the most effective exercise-based treatment for most types of knee pain, supported by strong evidence from the AAOS and ACR. Key exercises include straight leg raises, mini squats, step-ups, and terminal knee extensions. Hip strengthening is equally important because weak glutes contribute to abnormal knee alignment during movement.

Quadriceps strengthening is the cornerstone of knee pain rehabilitation. The quadriceps muscle group, particularly the vastus medialis oblique (VMO), provides dynamic stability to the patellofemoral joint and absorbs shock during weight-bearing activities. Straight leg raises are an excellent starting exercise: lie on your back, tighten the quadriceps, and lift the leg to 45 degrees, holding for 5 seconds. Perform 3 sets of 10 to 15 repetitions. Progress to mini squats (0 to 45 degrees of knee flexion) and step-ups as strength improves.

Hip strengthening is a critical but often overlooked component of knee pain management. Research published in the British Journal of Sports Medicine has demonstrated that hip abductor and external rotator weakness is strongly associated with patellofemoral pain syndrome, IT band syndrome, and knee valgus (knock-knee alignment). Clamshells, side-lying hip abduction, and single-leg balance exercises strengthen the gluteus medius and minimus, improving frontal plane knee control during walking, running, and stair climbing.

Low-impact aerobic exercise maintains cardiovascular fitness and joint mobility without excessive knee stress. The Arthritis Foundation recommends swimming, water aerobics, stationary cycling, and elliptical training for individuals with knee pain. Cycling is particularly beneficial because it strengthens the quadriceps through a large range of motion with minimal impact. Start with 10 to 15 minutes at low resistance and progress to 20 to 30 minutes as tolerated. The ACR strongly recommends regular physical activity for knee osteoarthritis management.

Hip abductor and external rotator weakness is strongly associated with patellofemoral pain[4]

• Straight leg raises: 3 sets of 10 to 15 reps, hold 5 seconds at top
• Mini squats (0 to 45 degrees): 3 sets of 10 to 12 reps with bodyweight
• Step-ups (6 to 8 inch step): 3 sets of 10 reps per leg
• Clamshells: 3 sets of 15 reps per side with resistance band
• Terminal knee extensions: 3 sets of 12 to 15 reps with resistance band
• Stationary cycling: 15 to 30 minutes at low to moderate resistance

What Treatments Are Available for Knee Osteoarthritis?

The ACR and AAOS recommend a stepped approach starting with exercise, weight management, and physical therapy. Pharmacologic options include topical and oral NSAIDs, intra-articular corticosteroid injections, and duloxetine. Hyaluronic acid injections have conditional recommendations. Total knee replacement is reserved for severe cases unresponsive to all conservative treatments.

First-line treatment for knee osteoarthritis centers on non-pharmacologic approaches. The 2019 ACR/Arthritis Foundation guidelines strongly recommend regular exercise including aerobic, strengthening, and flexibility activities. Weight loss of 5% or more body weight is strongly recommended for overweight individuals, as each pound of weight loss reduces knee joint loading by approximately 4 pounds during walking. Physical therapy provides supervised exercise progression and manual therapy. The use of a cane in the opposite hand, appropriate footwear with shock-absorbing insoles, and patellar taping have conditional recommendations.

Pharmacologic management follows a tiered approach. Topical NSAIDs (diclofenac gel) are strongly recommended as initial medication due to their favorable safety profile. Oral NSAIDs such as meloxicam, naproxen, or celecoxib are effective but carry gastrointestinal and cardiovascular risks with long-term use. Intra-articular corticosteroid injections provide short-term relief (4 to 12 weeks) and are conditionally recommended for acute flares. Duloxetine, an SNRI antidepressant, has evidence for knee OA pain through central pain modulation pathways and is conditionally recommended by the ACR.

Total knee arthroplasty (TKA) is one of the most successful orthopedic procedures, with over 90% of patients reporting significant pain relief and improved function. The AAOS recommends considering TKA when all conservative measures including exercise, weight management, medications, and injections have been exhausted. Over 750,000 total knee replacements are performed annually in the United States. Modern implants have survivorship rates exceeding 95% at 15 years. Post-surgical rehabilitation including progressive strengthening and range of motion exercises is critical for optimal outcomes.

The 2019 ACR/Arthritis Foundation guidelines strongly recommend regular exercise[5]

How Do Ligament and Meniscus Injuries Affect the Knee?

Ligament injuries such as ACL tears compromise knee stability during pivoting and cutting movements, while meniscus tears affect shock absorption and load distribution. Treatment ranges from physical therapy for partial tears and degenerative meniscal injuries to surgical reconstruction for complete ACL tears in active individuals who need to return to pivoting sports.

The anterior cruciate ligament (ACL) is the most commonly discussed knee ligament injury, with approximately 200,000 ACL injuries occurring annually in the United States according to the American Academy of Orthopaedic Surgeons (AAOS). ACL tears typically occur during noncontact pivoting, sudden deceleration, or landing from a jump. Patients often report hearing a pop followed by rapid knee swelling within 2 to 4 hours. ACL reconstruction using hamstring tendon or patellar tendon autograft is the standard surgical treatment for active individuals who wish to return to pivoting sports like basketball, soccer, and skiing.

Meniscus injuries require nuanced treatment decisions based on the tear pattern, location, and patient age. Tears in the outer one-third (red zone) of the meniscus have good blood supply and healing potential with repair. Inner zone tears (white zone) have poor vascularity and typically do not heal. A landmark randomized controlled trial published in the New England Journal of Medicine found that arthroscopic partial meniscectomy was no better than sham surgery for degenerative meniscal tears in middle-aged patients, shifting practice toward conservative management with physical therapy for this common condition.

Rehabilitation after ligament or meniscus surgery follows established protocols progressing through phases of protected range of motion, progressive strengthening, neuromuscular training, and sport-specific exercises. ACL reconstruction rehabilitation typically takes 9 to 12 months before return to full sport participation. The MOON (Multicenter Orthopaedic Outcomes Network) cohort study has provided extensive data on ACL reconstruction outcomes, showing that approximately 85% of patients return to some level of sport, though only 65% return to their pre-injury competition level.

Arthroscopic partial meniscectomy was no better than sham surgery for degenerative meniscal tears[6]

Can You Prevent Knee Pain and Injuries?

Many knee injuries and pain conditions are preventable through targeted exercise programs. The FIFA 11+ and similar neuromuscular training programs have been shown to reduce ACL injury risk by 50% or more. Maintaining quadriceps and hip strength, proper movement mechanics, appropriate footwear, and healthy body weight are the pillars of knee injury prevention.

Neuromuscular training programs are the most effective evidence-based strategy for preventing knee injuries, particularly ACL tears. The FIFA 11+ warm-up program, developed for soccer players but applicable to many sports, includes running exercises, balance training, plyometrics, and strengthening components performed for 20 minutes before practice. A meta-analysis published in the British Journal of Sports Medicine found that neuromuscular training programs reduced the risk of ACL injury by 50% and overall lower extremity injuries by 30%. These programs work by improving knee control, landing mechanics, and muscle activation patterns.

Maintaining a healthy body weight is essential for long-term knee health. The Framingham Osteoarthritis Study demonstrated that weight loss of approximately 11 pounds over 10 years reduced the risk of developing symptomatic knee osteoarthritis by more than 50% in women. For every pound of body weight lost, there is a 4-pound reduction in knee joint loading forces during walking. The ACSM recommends combining aerobic exercise with resistance training for sustainable weight management and joint protection.

Proper footwear and training principles also contribute to knee injury prevention. Shoes should provide appropriate support for your foot type and be replaced every 300 to 500 miles for running shoes. The 10% rule, which limits weekly training volume increases to no more than 10%, helps prevent overuse injuries such as patellofemoral pain syndrome, patellar tendinopathy, and iliotibial band syndrome. Cross-training by alternating high-impact activities with low-impact options like swimming or cycling reduces repetitive stress on the knee joint.

Neuromuscular training programs reduced the risk of ACL injury by 50%[7]

What Injections Are Used for Knee Pain?

The most common knee injections include corticosteroid injections for short-term inflammation relief, hyaluronic acid (viscosupplementation) for osteoarthritis, and platelet-rich plasma (PRP) as an emerging therapy. Corticosteroid injections are conditionally recommended by the ACR, while the evidence for hyaluronic acid and PRP continues to evolve.

Intra-articular corticosteroid injections are the most widely used injection therapy for knee pain, particularly for osteoarthritis and inflammatory conditions. They provide rapid anti-inflammatory effects within 24 to 48 hours, with pain relief typically lasting 4 to 12 weeks. Common formulations include triamcinolone acetonide and methylprednisolone. The ACR conditionally recommends corticosteroid injections for knee OA flares, but a 2017 randomized trial in JAMA found that repeated injections every 3 months for 2 years were associated with greater cartilage volume loss compared to saline injections, raising concerns about overuse.

Hyaluronic acid (HA) viscosupplementation involves injecting a gel-like substance into the knee joint to supplement the naturally occurring hyaluronic acid in synovial fluid. Treatment typically involves 1 to 5 injections depending on the product used. The AAOS does not recommend HA injections for knee OA based on inconsistent evidence, while the ACR provides a conditional recommendation against their use. However, some patients do experience meaningful relief, and the therapy continues to be widely used in clinical practice, particularly when other options have been exhausted.

Platelet-rich plasma (PRP) injections use concentrated growth factors from the patient's own blood to promote tissue healing. Emerging evidence suggests PRP may provide longer-lasting pain relief than corticosteroid injections for knee osteoarthritis. A 2021 meta-analysis published in the American Journal of Sports Medicine found that PRP was superior to hyaluronic acid for reducing pain at 12 months in knee OA. However, PRP is not yet covered by most insurance plans, protocols are not standardized, and larger randomized trials are needed before definitive recommendations can be made.

Repeated corticosteroid injections every 3 months were associated with greater cartilage volume loss[8]