Patellar tendinopathy (also known as jumper s knee) is a common injury in jumping athletes such as basketball and volleyball players. It is difficult to treat and may cause long lasting symptoms. Therefore prevention of this injury and the development of new treatment options are important. This thesis addresses both issues: prevention and treatment. For the development of preventive measures the following risk factors for jumper s knee were identified: weight, leg-length differences, a low arch-height of the foot, decreased flexibility of the lower limbs, jump power, a stiff landing technique, age, gender, playing position in volleyball players, and heavy physically demanding work. The second part of the thesis addresses the treatment of patellar tendinopathy with Extracoporeal Shockwave Therapy (ESWT). The effectiveness of two types of ESWT, focused ESWT and radial ESWT, was compared. The results show that there is no significant difference in effectiveness between the two types of ESWT. Both treatment groups improved on pain, function and sport participation over time, but did not fully recover. Further research is needed to uncover the pathophysiology of patellar tendinopathy. This may help to develop treatments that are more effective and that can be adapted to the stage of pathology.