Review Question - QID 108785

This patient has anterior knee pain after running, as well as sitting for a prolonged period of time, most consistent with patellofemoral pain syndrome (PFPS). The diagnosis is clinical and may be supported by reproduction of the pain with compression of the patella during knee extension.

This patient presents with a classic history for PFPS: she is a young female who has been running long distances. PFPS also tends to occur with prolonged sitting (“movie theater sign”) as well as ascending or descending stairs/hills. As this patient describes, the pain in PFPS is exacerbated by flexion of the knee and is anteriorly localized and dull. Given her history and description of the pain, PFPS is the most likely diagnosis. Compression of the knee while in extension is a helpful clinical tool to reproduce the pain and confirm the diagnosis, but this is not especially sensitive or specific. Empiric treatment with rest and NSAIDs, excluding aspirin, should relieve the pain and would also help confirm PFPS. Of note, her history of ACL injury is likely unrelated to this current episode.

Incorrect Answers:
Answer 1: Plain radiograph of the knee may be helpful in identifying pathologies such as osteoarthritis or occult patellar fractures. However, it is unhelpful in diagnosing PFPS, which has no radiographic findings. If empiric treatment does not relieve suspected PFPS after three or more months, plain radiograph may be performed to evaluate for other causes of pain.

Answer 2: MRI of the knee is often used for ligamentous injuries, such as torn ACL, but it would most likely be normal in PFPS. There is poor correlation between imaging and clinical findings, and MRI is not recommended if clinical history and exam are consistent with PFPS.

Answer 3: The ballotable patella test is performed by “milking” the knee capsule while the leg is extended and is useful for identifying large joint effusions. Effusions may result from arthritis, prepatellar bursitis, and infection, among other causes. Although this patient was recently treated for gonorrhea, there is no fever or clinical history to support the diagnosis of disseminated gonorrhea causing joint effusion.

Answer 5: The anterior drawer test involves pulling the shin forward while the patient is supine with flexed hip and knee. Laxity with this maneuver supports a diagnosis of ACL tear. Although she has a history of this injury, the patient currently does not recall an acute “popping” sensation or severe pain with walking, thus making ACL tear less likely.

Bullet Summary:
Patellofemoral pain syndrome classically presents with diffuse anterior knee pain after overuse or prolonged sitting; compression of the patella during knee extension will reproduce the pain.