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

Key Features

  • Effusion can occur with intra-articular pathology, such as osteoarthritis, and meniscus and cruciate ligament tears

  • Acute knee swelling (due to hemarthrosis) within 2 hours may indicate ligament injuries or patellar dislocation or fracture

  • Table 41–4 shows the differential diagnosis of knee pain

  • Table 41–5 outlines possible diagnoses based on the location of pain

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

Clinical Findings

  • Evaluation should begin with questions about duration and rapidity of symptom onset and the mechanism of injury or aggravating symptoms

  • Overuse or degenerative problems can occur with stress or compression from sports, hobbies, or occupation

  • A history of trauma as well as history of orthopedic problems requiring surgery should also be elicited

  • Symptoms of infection (fever, recent bacterial infections, risk factors for sexually transmitted infections [such as Neisseria gonorrhea] or other bacterial infections [such as Staphylococcus aureus]) should always be evaluated

  • Common symptomatic complaints

    • Grinding, clicking, or popping with bending may be indicative of osteoarthritis or the patellofemoral syndrome

    • "Locking" or "catching" when walking suggests an internal derangement such as meniscal injury or a loose body in the knee

    • Intra-articular swelling of the knee or an effusion indicates an internal derangement or a synovial pathology. Large swelling may cause a popliteal (Baker) cyst. Acute swelling within minutes to hours suggests a hemarthrosis, most likely due to an anterior cruciate ligament injury, fracture or patellar dislocation, especially if trauma is involved

    • Lateral "snapping" with flexion and extension of ...

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