There are many different kinds of straps, supports, and braces for use with knee problems. Wearing a band across the patellar tendon can support the tendon. This is called an infrapatellar strap or brace. Giving the tendon support may keep it from getting overused and inflamed.
Other similar bands may be used to guide the kneecap (patella) as it moves up and down in its groove. The strap helps spread the pressure on the patella over a wider area. It lifts the patella enough to relieve painful pressure.
Some knee braces offer dual support above and below the kneecap. The idea is to apply pressure on the tendon above and below the patella. Force from the quadriceps muscle large muscle over the front of the thigh) on the patellar tendon is less. The pressure is less because the alignment of the femur (thigh bone) and tibia (shin bone) is better.
These types of bands and supports still allow full motion and function, which makes them popular for use during practice and while competing. Wearing such a device may help you. Ask your coach, trainer, or therapist for advice on your situation before buying any device of this type.