Tests for Knee Cartilage Damage Don't Measure UpChondromalacia is a softening of the articular cartilage that protects the ends of bones and allows smooth movement in our joints. When the condition develops in the patella (kneecap), doctors sometimes call it chondromalacia patella. But do the symptoms people feel always come from changes in the surface of the patella? Some people report feeling symptoms of chondromalacia patella, but they have no visible changes in their cartilage. And some people feel no symptoms, yet they show changes within the cartilage. Go figure.
Doctors commonly check for this condition during a physical examination of the knee. But it is unclear how accurate these tests really are. These researchers compared the results of tests used in the physical exam to the results of an arthroscopic exam in 85 patients with knee problems. The arthroscope is a tiny TV camera inserted through a small incision. It allows doctors to look inside a joint to make a more accurate diagnosis. The researchers found that the physical tests just didn't measure up.
The researchers performed four different physical tests on the patients. They also measured the patients' thighs, to see if muscle atrophy could help in diagnosing the problem. Among the tests, only the flexion test had much relation to patellar chondromalacia. In a flexion test, the doctor holds the leg at its maximum flex point to see if the extra pressure under the kneecap causes pain. This test correctly identified people who did not have the condition 85% of the time--but it only identified people who actually had the condition 35% of the time. The authors tried to analyze the data a number of different ways to see if they could find any strong relationship between the tests and the condition, but they couldn't.
The authors conclude that none of the four physical tests is accurate enough for doctors to rely on in making a diagnosis of chondromalacia patella. Because it is invasive, arthroscopy is not a standard way to diagnose the problem. And changes in the bone under the layer of cartilage may be just as important in the development of chondromalacia, and these changes can't be seen through an arthroscope. Clearly, practitioners treating people with knee problems need tests that measure up to the task of diagnosing patellar chondromalacia.
Raimo O. Niskanen, MD, et al. Poor Correlation of Clinical Signs With Patellar Cartilaginous Changes. In Arthroscopy. March 2001. Vol. 17. No. 3. Pp. 307-310.
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