KNEE PAIN   44A

A 41-year-old man presents to urgent care clinic complaining of right medial knee pain. His pain began after he twisted his knee playing soccer 1 month ago. At the time, he had a significant amount of swelling and difficulty in bearing weight, both of which slowly resolved after 1 week of ice and rest. Since then, he has had both pain and frequent “locking” and “catching” of the joint when walking. On examination, he has tenderness to palpation at the medial joint line and a positive McMurray test result.

What are the salient features of this patient’s problem? How do you think through his problem?

Salient features: Medial knee pain; trauma with twisting; immediate effusion; “locking” and “catching” sensation; positive McMurray test result

How to think through: When evaluating any acute arthritis, begin with a mental checklist of systemic illnesses that can manifest as acute arthritis. Otherwise, acute joint pain will be erroneously attributed to trauma. If knee joint swelling and pain developed without clear-cut trauma, what study will likely provide the most important data? (Arthrocentesis.) Provided that the patient denies fevers and constitutional symptoms and the history supports trauma as the mechanism, the clinician’s tasks are to identify the injured structure, weigh the utility of imaging, and assess the need for early intervention. Key history to be elicited here include the mechanism of injury, ability to bear weight after the injury, degree of swelling and pain, and presence of “locking” and “catching.” The exact location of the pain (best obtained by asking the patient to point with one finger) should also be assessed. The tempo of swelling onset was not reported. (When swelling develops rapidly after injury, hemarthrosis should be considered, possibly from an acute ligamentous tear.) “Catching” and “locking” strongly suggest what pathology? (A meniscal tear.) What internal knee joint structures should be evaluated on the physical examination? (Ligaments, meniscus.) How is the meniscus assessed? (Two commonly performed tests load and stress the meniscus: McMurray test and Thessaly test.) What imaging modality is preferred if meniscus injury is suspected? (Magnetic resonance imaging [MRI].)

KNEE PAIN   44B

What are the essentials of diagnosis and general considerations regarding knee pain?

Essentials of Diagnosis

Examination of range of motion, effusions, meniscus, and ligaments

Evaluation of aspirated joint fluid if indicated

General Considerations

Injuries may be caused by trauma, inflammation, infection, or degenerative changes.

Ligaments, menisci, synovium, or bursa may be affected.

Effusions can occur with intraarticular pathology (e.g., osteoarthritis, tears of meniscus or cruciate ligament, or patellar fracture).

Overuse syndromes of the knee, such as anserine bursitis, iliotibial band syndrome, and popliteal or patellar tendinitis, occur often in runners who overtrain or who are not properly conditioned.

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