The major bones of your leg, the femur and tibia, may be out of alignment at the knee joint.
rob1880 mentioned seeing a chiropractor, and I agree, a good chiropractor can usually fix this in a few seconds, if this is the problem.
Plyometrics and basketball are both high impact on the joints. When you do plyometrics, are they concentric or eccentric?
I would also be very careful to check your technique on all leg exercises in the weight room, any breaks in form, can cause huge problems over time.
Most problems in lifting can be solved by either pulling harder, or pushing harder.