Knee extensor mechanism tendinopathy, including patellar and quadriceps tendinopathy, is common among athletes and those involved in jumping sports. It is largely a clinical diagnosis that presents as anterior knee pain and stiffness with associated tenderness over the affected tendon. Imaging modalities, including ultrasound and/or magnetic resonance imaging, may be helpful with the diagnosis of difficult cases or in the planning of interventional procedures. Focused and structured rehabilitation using eccentric or heavy slow resistance exercise in conjunction with load management is important for recovery. Adjuvant therapies (e.g., injections or surgery) may be necessary in recalcitrant cases or those with insufficient response to rehabilitation efforts. Prevention strategies focus on improving biomechanics, landing mechanism and lower-extremity balance, flexibility, and strength.