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For further information, see CMDT Part 41–06: Musculoskeletal Injuries of the Knee

Key Features

Essentials of Diagnosis

  • Degeneration of joint cartilage

  • Pain with bending or twisting activities

  • Swelling

  • Loss of active and passive range of motion in severe osteoarthritis (OA)

General Considerations

  • Cartilage loss and OA symptoms are preceded by damage to the collagen-proteoglycan matrix

  • The etiology of OA is often multifactorial including

    • Previous trauma

    • Prior high-impact activities

    • Genetic factors

    • Obesity

    • Rheumatologic or metabolic conditions


  • The incidence of knee OA in the United States is 240 per 100,000 person-years

  • The prevalence of OA will likely grow to 70 million persons by 2030 as the number of persons over age 65 years increases

Clinical Findings

  • Pain in the affected joint with loading of the joint or at the extremes of motion.

  • Swelling, grinding, catching, and locking

  • Pain can also produce the sensation of "buckling" or "giving way" due to muscle inhibition (Tables 41–4, 41–5, and 41–6)

  • As the joint degeneration becomes more advanced, the patient loses active range of motion and may lose passive range of motion as well

  • As the condition worsens, patients have an increasingly limited ability to walk

    • Symptoms include pain with bending or twisting activities and going up and down stairs

    • Swelling, limping, and pain while sleeping are common complaints, especially as OA progresses

Table 41–4.Differential diagnosis of knee pain.
Table 41–5.Location of common causes of knee pain.

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