Knee Pain
Basics
Description
A common outpatient complaint with a broad differential
- Knee pain may be acute, chronic, or an acute exacerbation of a chronic condition.
- Trauma, overuse, and degenerative change are the frequent causes.
- A detailed history, including patient’s age, pain onset and location, mechanism of injury, and associated symptoms, can help narrow the differential diagnosis.
- A thorough and focused examination of the knee (as well as the back, hips, and ankles) helps to establish the correct diagnosis and appropriate treatment.
Epidemiology
Incidence
- Knee complaints account for 12.5 million primary care visits annually.
- The incidence of knee osteoarthritis (OA) is 240 cases per 100,000 person-years.
Prevalence
- The knee is a common site of lower extremity injury.
- Patellar tendinopathy and patellofemoral syndrome are the most common causes of knee pain in runners.
- OA of the hip/knee is the 11th cause of global disability and the 38th most common cause of disability-adjusted life years (DALYs).
Etiology and Pathophysiology
- Trauma (ligament or meniscal injury, fracture, dislocation)
- Overuse (tendinopathy, patellofemoral syndrome, bursitis, apophysitis)
- Age (arthritis, degenerative conditions in older patients; apophysitis in younger patients)
- Rheumatologic (rheumatoid arthritis [RA], systemic lupus erythematosus [SLE])
- Crystal arthropathies (gout, pseudogout)
- Infectious (bacterial, postviral, Lyme disease)
- Referred pain (hip, back)
- Vascular (popliteal artery aneurysm, deep vein thrombosis)
- Others (tumor, cyst, plica)
Risk Factors
- Obesity
- Malalignment
- Poor flexibility, muscle imbalance, or weakness
- Rapid increases in training frequency and intensity
- Improper footwear, training surfaces, technique
- Activities that involve cutting, jumping, pivoting, deceleration, kneeling
- Previous injuries
General Prevention
- Maintain body mass index <25 kg/m2.
- Proper exercise technique, volume, and equipment; avoid overtraining.
- Correct postural strength and flexibility imbalances.
Commonly Associated Conditions
- Fracture, contusion
- Effusion, hemarthrosis
- Patellar dislocation/subluxation
- Meniscal or ligamentous injury
- Tendinopathy, bursitis
- Osteochondral injury
- OA, septic arthritis
- Muscle strain
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Citation
Domino, Frank J., et al., editors. "Knee Pain." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116899/all/Knee_Pain.
Knee Pain. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116899/all/Knee_Pain. Accessed October 3, 2024.
Knee Pain. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116899/all/Knee_Pain
Knee Pain [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 October 03]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116899/all/Knee_Pain.
* Article titles in AMA citation format should be in sentence-case
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