Discussion

Jumper's knee is a degenerative condition of the knee extensor mechanism caused by overuse. While sometimes used synonymously for patellar tendinopathy alone, it is actually a tendinopathy affecting the distal insertion of the quadriceps tendon (25% of cases) or the patellar tendon.1 ,2 Jumper's knee is commonly seen in sports involving repetitive jumping, such as basketball and volleyball. In professional athletes, the prevalence is 14%.3 In professional basketball and volleyball players, the prevalence is 32% and 45%,3 respectively.

The multilayered quadriceps tendon connects the four quadriceps muscles to the superior pole of the patella. The patellar tendon connects the non-articulating base of the patella with the tibial tubercle. It is continuous with the quadriceps femoris tendon through the superficial rectus femoris tendon fibres that run over the anterior surface of the patella. The patellar and quadriceps tendons are therefore considered to be one anatomic entity consisting of fibrocartilaginous tissue, mainly types I and II collagen fibres.

Both tendons do not have a paratenon, but they receive blood supply secondarily from the patellar vascularisation. Quadriceps tendon blood supply is provided by three vascular arcades, resulting in a relatively hypovascular zone 1–2 cm superior to the patella.2 Vascularisation of the patellar tendon is mainly provided by Hoffa's fat pad, directly posterior to the tendon. This leaves the distal insertion relatively hypovascularised.4 This zone in either the quadriceps or patellar tendon might be more susceptible to damage.

Quadriceps and patellar tendinopathy are thought to be caused by …