The kneecap or patella is designed to fit in the middle over the femur (thigh bone). This forms the patellofemoral joint. During normal motion, the patella moves up and down along a groove in the femur. This central position and tracking is optimal for joint motion and function.
If the patella is slightly off-center in either direction, then there is an increased risk of uneven load and force on the patellofemoral joint. Over time and with repetitive motion, patellofemoral pain (PFP) may develop.
Women seem to be at increased risk for this problem. Even in females without PFP, the patella is often off center laterally (away from the midline). But it's likely there are other factors as well. A laterally displaced patella doesn't automatically mean the athlete will have knee pain or other knee problems.