How can I reduce swelling of the kneecap area from sports?

Ice and exercise. Most anterior knee pain is due to a imbalance in muscle strength in the quads plus a few other factors. Apply ice after exercise and start working on quad and hamstring stretching and strengthening. Try to focus on building strength in the medial quads while stretching the it band complex. Check google for it band stretches and vastus medialis exercises. Too much to cover here.