X-rays and MRIs don’t always show the doctor everything. However, when it comes to damage to the cartilage after a kneecap (patella) injury, arthroscopy is quite helpful.
When the patella dislocates, there can be damage to the cartilage in several places. First, the cartilage behind the patella itself can get cracked. And the cartilage covering the end of the thighbone (femur) can take a beating.
Previous studies used X-rays after a patellar dislocation to look for damage to the cartilage. It wasn’t until an arthroscope was used to look for cartilage damage that doctors realized how often this happens. The arthroscope is a slender instrument with a tiny TV camera on the end. It can be inserted right inside the knee joint to show the doctor what’s going on.
The authors of this study report a 95 percent chance of cartilage damage after patellar dislocation. They describe the type and location of the damage. This will alert other doctors where to look and what to look for.
They also report that the cracks may look small or very fine. However, the cracks move and get larger with any movement. The researchers conclude that high contact forces from patellar dislocation can cause cracks in the cartilage of the knee. It’s more common than previously thought. Arthroscopy is the test of choice to look for cartilage damage after patellar dislocation.