Patella tip syndrome [a.k.a. runner's knee, jumper’s knee, or patellar tendonitis] develops when the patellar tendon (patellar ligament) is irritated by unaccustomed or excessive tension forces.
For example, in sports that involve intensive jumping (basketball, volleyball), activities that involve many stop-and-go movements (tennis, badminton) or quick changes in direction (football).
Patella tip syndrome is also widespread among runners, which is why it also called jumper's knee or runner's knee. The pain is felt around the tip of the kneecap.