Commentary

Can a primary care practitioner use the patient history and physical examination to correctly identify those with traumatic knee pain who would benefit from surgical intervention? In an excellent meta-analysis, Scholten et al provide evidence that joint tenderness or swelling does not predict the presence or absence of a torn meniscus, and a positive McMurray test result is minimally predictive of a meniscal tear. Other issues relating to the authors' research question require further attention.

First, most studies did not involve primary care providers. This omission biases the results toward a higher prevalence of meniscal tears and does not tell us whether primary practitioners do an examination similar to specialists. Second, the predictive value of such key questions in the patient's history as locking of the knee with flexion, the motion of injury, giving way of the knee, and knee swelling remains elusive. Third, methodological flaws may bias results. In 11 of 13 studies, the physical examination and the diagnostic standard (arthroscopy and MRI) were not assessed blindly, and patients with clinical suspicion of a meniscal lesion were more likely to have had surgery or an MRI. Finally, we do not know whether any test distinguishes a large traumatic tear (which will benefit from surgery) from a degenerative tear (which will respond to conservative management).

Should a primary provider continue to use joint effusion, tenderness, or a McMurray test in their physical examination? Until a large, well controlled prospective study involving primary care patients looks at the predictive power of both the patient history and the physical examination, we do not know for sure. In the meantime, it appears that physical examination is useful only when combined with the patient's history. For example, a 35 year old patient with an acute twisting injury, painful locking, and giving way has a greater chance of having a large, acute, surgically correctable meniscal tear than is a 56 year old patient who notes that a trivial squat produced pain and giving way. In the 35 year old patient, a positive McMurray test result increases the likelihood of surgical benefit, whereas in the 56 year old patient it adds no information.