There are several different types of overuse pain syndromes in and around the knee that can be associated with all sorts of vigorous exercise (not just racquetball). Probably the best thing to do would be to go to see your primary care doctor
. They will be able to evaluate your knees to make sure there is not a serious problem (such as a ligament tear). They will also be able to help you determine which type of pain syndrome you may have.
Two very common syndromes are patellofemoral pain syndrome (runner's knee) and iliotibial band syndrome.
Patellofemoral pain syndrome occurs when imbalance between muscles of the thighs creates improper tracking of the patella (knee cap), leading to degenerating of the cartilage and pain, especially with sitting or knee bending. This can usually be treated with rest, anti inflammatories, and strengthening exercises to the quads.
Iliotibial band syndrome is an overuse injury
of the connective tissue band running down the outer thigh to the knee. It is commonly causes by imbalance in the muscles that move the thigh in and out from the body, and it can be treated with stretching exercises and strengthening exercises.
Start by talking to your primary care doctor!