The diagnosis of a meniscal tear is usually made by the patient telling the physician about the type of injury, the symptoms, and the physician’s examination. The x-ray is helpful After ACL Injury in determining other factors which may be related to other diagnoses.
X-rays show only the bone, and menisci, being cartilage, have no bone in them. Plain x-rays will not make a diagnosis of a torn cartilage. There is an old x-ray test called an arthrogram in which dye is injected into the knee by a radiologist and the x-rays are made with the dye in the knee. The dye highlights the tear and then can be seen on plain x-rays.
A newer and much more sensitive test is called MRI, or magnetic resonance imaging. As the name implies, a magnet is used to form images of the structures inside the knee. These images are various “shadows” of the structures based on the different amount of water in each different type of tissue. Studies have shown that MRIs are 90 to 95% accurate in being able to determine if there is a tear in a meniscus. In some very specific cases, I may recommend an MRI arthrogram. In those cases, a special dye is injected into the knee and then the MRI is performed. Like the old arthrograms, the dye highlights the tears and injured regions within the knee, making them more easily seen on MRI.
What else could be wrong besides a torn cartilage?
There are several conditions which can mimic a torn cartilage very closely. The first and most common condition is arthritic changes in the knee. It is also possible to have both. The arthritis can be on the same side of the knee with the torn cartilage or the other side, or behind the kneecap. X-ray is helpful in making the diagnosis of arthritis, but it does not show the earlier stages. The second is an abnormally tight or thick band of joint lining which might be developmental, congenital, or secondary to trauma, can mimic the signs and symptoms of a torn cartilage. The medical term for this is plica or shelf.