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Knee News

Swelling in the Knee: What Does It Mean?

When a patient presents to his or her general practitioner (GP) with a knee injury, the doctor relies on the patient's history (what happened) and a physical exam (clinical tests) to figure out what's wrong. Is there swelling in the joint? Is there damage inside the joint? Can a physician even tell these things with a history and physical exam (H&PE)? When are additional tests such as X-rays or MRIs needed?

Researchers from the Netherlands take on these questions in a study of 134 patients with a traumatic knee injury. Most (but not all) injuries were sports-related. Each patient was questioned about their symptoms and then examined by a physical therapist using a standard series of tests for the knee. Tests included range-of-motion, palpation, stability, and meniscal (knee cartilage) tests.

Three special tests were done to look for effusion (swelling). The first was palpation of the popliteal fossa (back of the knee). The second was a palpatory test called the minor effusion test. The examiner pushes the fluid in the knee from one side to the other. And the third test of effusion was the Ballottement test. The examiner presses the patella (kneecap) down (the patient's leg is extended or straight during the test). When there is swelling under the patella, the kneecap moves down, clicks as it touches the bone, and then floats back up.

How accurate are these tests? Can a general practitioner rely on them to make the diagnosis? Are all three tests required? Or is there one test that's better than the others to detect damage inside the knee? One way to answer these questions is to test each patient, take an MRI, and then compare the results between the two tests. The MRI is a very accurate test for effusion of the knee.

Analysis of the data showed that three-fourths of the patients with moderate to severe effusion had a serious knee injury as shown by the MRI. The injury was either a torn ligament inside the knee or damage to the meniscus (cartilage). In 62 per cent of the cases, it was possible to tell there was joint effusion using the ballottement test. And they noted that when effusion was present, damage inside the knee was likely.

There were a few yes, but messages from the study. For example, the authors pointed out that it is possible to have a knee injury without swelling. It's also possible that swelling might be present but the tests used here would still be negative.

In the end, it looks like a positive patient report (the patient thinks the knee is swollen) combined with a positive ballottement test is highly indicative of damage inside the knee. Combining results of the history and physical exam is a reliable way to assess knee effusion after a knee injury. X-rays are taken if the physician suspects bone fracture. Conservative (nonoperative) care is recommended otherwise. MRIs are suggested when there is doubt about the diagnosis.

Referral to an orthopedic surgeon is advised if there is clicking of the knee and/or the general practitioner has reason to believe there is internal derangement of the knee such as a ligament or meniscal tear.


Marlous Kastelein, MD, et al. Diagnostic Value of History Taking and Physical Examination to Assess Effusion of the Knee in Traumatic Knee Patients in General Practice. In Archives of Physical Medicine and Rehabilitation. January 2009. Vol. 90. No. 1. Pp. 82-86.

01/22/2009

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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