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When I listened to other people—who seemed to have trouble even though their [knee replacements] went well—[I learned that] they didn’t make the commitment to rehab . . I can walk forever now—pain-free . . I can hit a tennis ball again.
Billie Jean King, six years after her 2010 knee replacements
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Although acute knee injuries and anterior knee pain are very common presentations in sports and exercise medicine practice, patients presenting with lateral, medial or posterior knee pain are not uncommon and can provide the clinician with both diagnosis and treatment challenges.
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Athletes can present with the chief complaint of lateral knee pain for a number of underlying problems, including: lateral meniscus tears and cysts; bone bruises or cartilage injuries of the lateral compartment; patellofemoral syndrome or patellar instability; injuries of the posterolateral corner structures (popliteus, lateral collateral ligament, mid third capsular ligament anterolateral ligament); biceps insertional tendinopathy and injuries; tibiofibular joint instability; and iliotibial band syndrome at the knee.
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Lateral knee pain (Fig. 37.1) is a particularly common problem among distance runners and cyclists, the most common cause of lateral knee pain being iliotibial band friction syndrome (ITBFS). Training errors as well as alignment and biomechanical abnormalities can precipitate ITBFS. Patellofemoral syndrome (Chapter 36) or instability may also present as lateral knee pain. In the older active person, lateral meniscus degeneration or lateral compartment osteoarthritis should be more strongly considered as part of the differential diagnosis. For sprinters and footballers, overuse injuries of the biceps femoris tendon and its insertion onto the fibula should be considered more highly in the differential diagnosis. The biceps femoris tendon may suffer compression and irritation as it passes posterolaterally to the knee and inserts into the head of the fibula, likely as a result of the repetitive flexion and rotation demands on the knee. Injuries of the superior tibiofibular joint may also cause lateral knee pain.
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The astute clinician should always be conscious of the potential of associated injuries or referred pain involving the lateral aspect of the knee. Ligamentous injuries of the posterolateral corner are rarely isolated and frequently involve injury to the ACL or PCL. Lateral knee pain may also occur as a result of referred pain from the lumbar spine. The causes and differential diagnoses of lateral knee pain are shown in Table 37.1.
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