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Knee Pain

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.
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Table 41–4. Differential diagnosis of knee pain.

Mechanical dysfunction or disruption

 Internal derangement of the knee: injury to the menisci or ligaments

 Degenerative changes caused by osteoarthritis

 Dynamic dysfunction or misalignment of the patella

 Fracture as a result of trauma

Intra-articular inflammation or increased pressure

 Internal derangement of the knee: injury to the menisci or ligaments

 Inflammation or infection of the knee joint

 Ruptured popliteal (Baker) cyst

Peri-articular inflammation

 Internal derangement of the knee: injury to the menisci or ligaments

 Prepatellar or anserine bursitis

 Ligamentous sprain
Table 41–5.Location of common causes of knee pain.
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Table 41–5. Location of common causes of knee pain.

Medial knee pain

 Medial compartment osteoarthritis

 Medial collateral ligament strain

 Medial meniscal injury

 Anserine bursitis (pain over the proximal medial tibial plateau)

Anterior knee pain

 Patellofemoral syndrome (often bilateral)

 Osteoarthritis

 Prepatellar bursitis (associated with swelling anterior to the patella)

 “Jumper’s knee” (pain at the inferior pole of the patella)

 Septic arthritis

 Gout or other inflammatory disorder

Lateral knee pain

 Lateral meniscal injury

 Iliotibial band syndrome (pain superficially along the distal iliotibial band near lateral femoral condyle or lateral tibial insertion)

 Lateral collateral ligament sprain (rare)

Posterior knee pain

 Popliteal (Baker) cyst

 Osteoarthritis

 Meniscal tears

 Hamstring or calf tendinopathy

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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