A 26-year-old marathon runner presents to the sports medicine clinic with a 3-week history of aching pain over the lateral aspect of her right knee. She reports that the pain typically begins after the third mile of her run and becomes sharp and localized when she is running downhill. She denies any history of direct trauma, knee locking, or knee instability. On physical examination, there is no joint effusion, and the McMurray and Lachman tests are negative. There is exquisite tenderness to palpation approximately 2 cm superior to the lateral joint line. When pressure is applied to this area while passively moving the patient's knee from 90° of flexion to full extension, the patient’s familiar pain is reproduced at approximately 30° of flexion.
Which of the following is the most likely diagnosis?
The correct answer is:
A) Iliotibial band syndrome
The patient is presenting with iliotibial (IT) band syndrome, a common overuse injury among runners and cyclists. It is caused by repetitive friction of the distal IT band as it slides over the lateral femoral epicondyle during knee flexion and extension. The pain is typically most acute when the knee is at approximately 30° of flexion, which is known as the impingement zone. The physical examination maneuver described in the vignette is Noble’s test, which is highly suggestive of the condition. Another common test used is Ober’s test, which assesses for tightness of the IT band by checking for limited adduction of the hip while the knee is flexed. Risk factors include downhill running, worn-out shoes, and weakness in the hip abductors (gluteus medius), which leads to increased compensatory tension in the IT band.
Answer choice B: Lateral collateral ligament (LCL) tear, is incorrect. LCL injuries usually result from a varus stress to the knee. While they cause lateral pain, they typically present with laxity on a varus stress test and tenderness directly over the ligamentous attachments, rather than the friction pain at 30° of flexion seen in IT band syndrome.
Answer choice C: Lateral meniscus tear, is incorrect. While a lateral meniscus tear also causes lateral pain, it is typically associated with a history of a twisting injury, mechanical symptoms like locking or catching, and tenderness specifically along the joint line rather than superior to it. A positive McMurray test would be expected.
Answer choice D: Patellofemoral pain syndrome, is incorrect. This condition presents with anterior knee pain, often described as retro-patellar. It is exacerbated by activities that load the patellofemoral joint, such as squatting or sitting for long periods, and would typically have a positive patellar compression test.
Answer choice E: Pes anserine bursitis, is incorrect. Pes anserine bursitis involves inflammation on the medial aspect of the knee, at the common insertion of the sartorius, gracilis, and semitendinosus tendons on the proximal tibia.
Key Learning Point
Iliotibial band syndrome is the most common cause of lateral knee pain in runners. It is characterized by localized tenderness over the lateral femoral epicondyle and a positive Noble’s test. Initial management involves activity modification, NSAIDs, and physical therapy focused on gluteus medius strengthening and IT band stretching.
