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Update your Knowledge with MKSAP 18 Q&A: Answer and Critique

Answer

A: Iliotibial band syndrome

Educational Objective

Diagnose iliotibial band syndrome.

Critique

The most likely diagnosis is iliotibial band syndrome (ITBS). ITBS is a common cause of lateral knee pain in runners and can also occur in patients with significant leg length difference, an excessively pronated foot, genu varum, or gluteal muscle weakness. Patients with ITBS have pain that is poorly localized to the lateral knee and distal thigh. Initially, the pain is present only after prolonged activity (such as running) that involves repeated knee flexion and extension. As the condition progresses, the pain occurs earlier in the course of activity and may eventually be present at rest. On examination, there is often tenderness to palpation 2 to 3 cm proximal to the lateral femoral condyle. Patients also frequently have weakness with hip abduction. Reproduction of the pain with knee extension from 90 degrees to 30 degrees with the examiner's thumb exerting pressure on the lateral femoral epicondyle (Noble test) supports the diagnosis of ITBS. Initial treatment consists of activity modification, ice application, and NSAIDs to reduce inflammation. Once inflammation subsides, stretching and then strengthening exercises are indicated.

This patient lacks history of trauma, joint instability, lateral joint line tenderness, or increased laxity with varus force. Lack of these features argues against the presence of a lateral collateral ligament tear.

The lack of prior trauma and absence of catching, grinding, and locking all argue against a meniscal tear, as does the absence of an effusion on examination.

Meralgia paresthetica is due to entrapment of the lateral femoral cutaneous nerve and causes paresthesias on the anterolateral thigh. Risk factors include diabetes mellitus, obesity, pregnancy, and tight clothing or belts around the waist. This patient's findings are not consistent with meralgia paresthetica.

Key Point

Patients with iliotibial band syndrome report diffuse, poorly localized lateral knee and distal thigh pain; there is often tenderness to palpation 2 to 3 cm proximal to the lateral femoral condyle.

Bibliogrpahy

Baker RL, Fredericson M. Iliotibial band syndrome in runners: biomechanical implications and exercise interventions. Phys Med Rehabil Clin N Am. 2016;27:53-77. [PMID: 26616177] doi:10.1016/j.pmr.2015.08.001

Back to the March 2019 issue of ACP International