Amy Norton writing in Reuters reported that volleyball players, compared to six other recreational sports, have the highest incidence of patellar tendinopathy, or jumper's knee. Researchers attribute this to the hard surfaces and constant jumping in volleyball. Anecdotes suggest that beach volleyball players have fewer knee problems. Researchers recommend rest, early treatment, and having physical therapy before the tendon degenerates. The study was published in the American Journal of Sports Medicine. And don't forget about platelet-rich plasma PRP which is I believe the treatment of choice!