Damage to the meniscus is fairly easy to diagnose based on the patient's history and a few clinical tests. The most common history is a twisting injury of the knee with the foot planted firmly on the ground. The knee is usually bent when this happens. Pain occurs along with swelling that comes and goes and a locking sensation for some patients.
Some of the tests used by doctors, therapists, and athletic trainers to test for meniscal tears have a high rate of false-positive findings. This means the test is positive for a meniscal tear when no tear is present.
No test is fool proof but joint line tenderness along the outer edge of the joint can be safely used to detect a lateral meniscus tear. Joint line tenderness for any meniscal tear is less reliable when there's an anterior cruciate ligament (ACL) tear also present at the same time.
The most reliable test may be a new one. The Thessaly test has been shown to be 94 to 96 percent accurate with knee meniscus. The need for an expensive MRI may be replaced by this new first line screening exam.