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I saw the physician's assistant for an evaluation of knee pain and swelling in my right knee. It started right after I got knocked over by the neighbor's dog chasing my dog. She did a good exam, but no X-rays or MRIs. Should I ask for these tests to be sure?

Studies show that relying on the patient's history and a physical exam is very likely to yield the correct diagnosis. Patient's who report swelling often have some type of internal derangement (damage inside the joint). When that's the case, the examiner conducts a few additional clinical tests known for their reliability and validity in diagnosing problems. Tests usually include knee range-of-motion, palpation, stability, and meniscal (knee cartilage) tests. Three special tests are often done to look for effusion (swelling). The first is palpation of the popliteal fossa (back of the knee). The second is 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 is 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. 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 there is suspicion of a 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 physician's assistant has reason to believe there is internal derangement of the knee such as a ligament or meniscal tear.

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