Commentary & Perspective

Commentary & Perspective on
"Tumors About the Knee Misdiagnosed as Athletic Injuries"
by D. Luis Muscolo, MD, et al.

Commentary & Perspective by
Dempsey Springfield, MD*,
Mount Sinai Medical Center, New York, NY

There are three major reasons for the phenomenon discussed in this article. First, patients presenting with symptoms related to the lower extremities tend to associate the symptoms with a joint injury. Abnormalities in the lower extremity, from those in the pelvis to those in the proximal tibia, can, and often do, manifest as knee pain. Second, an injury is the most logical cause of pain, and patients often seem to relate a new symptom to some sort of injury. Third, even individuals who are not physically active and who cannot remember a specific injury will report some "sport" activity that they consider to be related to their symptom. This leads the physician to believe that the patient actually had an injury and that the symptom presented did result from that injury or activity. Post hoc ergo ad hoc.

In most cases, the patient is correct: the symptom is due to an injury or activity and the joint is the source of the problem. For those patients in whom this is not the case, a careful history and physical examination will reveal that the symptom is not related to the injury that the patient has indicated or that the source of the symptom is not the joint but tissues near the joint. In the series of Muscolo et al., it is likely that many of the 642 patients who had a tumor about the knee and were not misdiagnosed as having an injury may have stated on presentation that they had knee pain due to an injury. In those cases, the diagnosis may have been made correctly by the referring physician. One of the interesting questions that Muscolo et al. did not answer was why the tumors in the group of twenty five patients were not correctly diagnosed initially. We can only speculate.

Muscolo et al. found that none of the patients with a missed tumor had had a magnetic resonance imaging (MRI) scan before the initial surgery. The authors suggested that if an MRI had been done, then the correct diagnosis would have been made. Albeit, in my recent experience, a patient who had an osteoblastoma in the distal femur underwent an arthroscopic lateral release before the correct diagnosis was made. He had had an MRI prior to the arthroscopic lateral release and, although in retrospect the osteoblastoma was visible on the MRI scan, it was initially missed by the radiologist and by the orthopaedist. Admittedly, it is probably not practical to perform an MRI for every patient who presents with knee symptoms. Also, it is my experience that many abnormalities found on an MRI do not relate to the patient's symptoms, and these "findings" may result in inappropriate treatment more often than the omission of routine MRI studies would. We do not have the data to judge whether routine diagnostic MRIs are appropriate for symptoms of knee pain. It is certain that if an MRI is to be accurately interpreted, the findings must be correlated with the patient's symptoms and the findings on physical examination.

The most effective preventative for misdiagnosis of a tumor about the knee is to remember that it is possible for a patient with a tumor to present with symptoms that are similar to those of a knee injury. Usually a careful history with very specific questions about the onset of the pain, the type of injury, the progression of symptoms, and the precise location of the pain will reveal differences between the symptoms of a tumor and those of an intra-articular abnormality. The symptoms of a patient with a tumor generally progress with time and are often worse at night. On presentation, the patient often reports that the pain did not start immediately after the injury thought to be the cause of the symptoms and that he or she initially did not think that the injury was significant.

Next, the findings of the physical examination of the knee can help to differentiate between tumor and an intra-articular abnormality. Often the patient will report knee pain but when asked to point to the specific area of pain, he or she indicates an anatomic site unrelated to the joint. Examination of the indicated location reveals tenderness or a mass. The patient may have an effusion but not true findings of an intra-articular abnormality. Of course, there are patients with torn or degenerative menisci or torn ligaments who also have a tumor. These cases are very rare but can be the most difficult to diagnose.

Finally, the initial evaluation should include plain radiographs. Virtually all patients with knee symptoms, and certainly all patients being considered as candidates for surgery, should have at least two plain radiographs (an anteroposterior view and a lateral view). The radiographs must be examined carefully for both bone and soft-tissue abnormalities. Radiographs of poor quality should not be accepted; rather, repeat radiographs should be made. The possibility of a bone or soft-tissue lesion should be considered and investigated. When the symptoms, physical findings, and plain radiographs are not well correlated, further evaluation is needed. When localization of the anatomic site of the symptom proves difficult and the findings are normal on plain radiographs, technetium-99 bone scans can be performed. Computed tomographic scans are the most effective tools for the evaluation of subtle soft-tissue calcifications or small bone lesions. Magnetic resonance imaging is the best tool for evaluation of the soft tissues, of radiolucency, or subtle bone lesions.

Even with these diagnostic measures, it is possible that a tumor will be missed initially. The dangers then are that the treatment of the suspected injury will adversely affect the patient's prognosis or that the delay in making the correct diagnosis will result in an adverse outcome. The realization of these dangers may be the most important finding of this study, with implications for treatment. If during an operation for treatment of a suspected injury or abnormality, an unexpected tumor is found, the adverse effects of an unplanned biopsy should be considered. Usually it is better to delay the biopsy until an appropriate evaluation has been performed. If the expected intraoperative findings are not found or if the results of the surgical treatment are not as successful as can be reasonably expected, the physician should rethink the original diagnosis and re-evaluate the patient.

Mistakes are part of the practice of medicine. Reducing the number of mistakes and controlling their effects is all that we can do. Careful and thoughtful evaluation and the ability to question one's assumptions are always important in the management of patients.

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.