Summary Quadriceps tendonitis is inflammation of the suprapatellar tendon of the quadriceps muscle associated with activity-related anterior knee pain. Diagnosis is made clinically with tenderness to palpation at the quadriceps tendon insertion at the superior pole of the patella. Treatment is generally nonoperative with resting, ice, activity modifications and physical therapy to focus on hamstring, quadriceps and core strengthening. Epidemiology Demographics 8:1 male-to-female ratio more common in adult athletes Risk factors jumping sports basketball volleyball athletics (e.g., long jump, high jump, etc) Etiology Pathophysiology mechanism of injury occurs as the result of repetitive eccentric contractions of the extensor mechanism pathoanatomy microtears of the tendon most commonly at the bone-tendon interface Associated conditions Jumper's knee patellar tendonitis more commonly affects the insertion of the patella tendon at the patella. less commonly the insertion at the tibial tubercle Quadriceps tendinosis chronic quad tendon degeneration with no inflammation Anatomy Knee extensor mechanism quadriceps muscles rectus femoris, vastus medialis, vastus lateralis, vastus intermedius quadriceps tendon common trilaminar tendon of quadriceps muscles anterior layer = rectus femoris middle layer = vastus medialis and vastus lateralis deep layer = vastus intermedius Vascular supply medial, lateral and peripatellar arcades Innervation innervated by muscular branches of the femoral nerve (L2, L3, L4) Presentation History overuse injury in a jumping athlete recent increase in athletic demands or activity often a recurring injury Symptoms pain localized to the superior border of patella worse with activity associated swelling Physical examination inspection knee alignment swelling palpation tenderness to deep palpation at quadriceps tendon insertion at the patella palpable gap would suggest a quads tendon tear patellar subluxation motion pain with resisted open chain knee extension able to actively extend the knee against gravity Imaging Radiographs recommended views AP and lateral of knee optional views Sunrise or Merchant views for patella instability findings usually normal may see tendon calcinosis in chronic degeneration measurement evaluate knee alignment for varus/valgus angle evaluate for patellar height (patella alta vs baja) for suspected quadriceps tendon rupture Blumentsaat's line should extend to inferior pole of the patella at 30 degrees of knee flexion Insall-Salvati method normal between 0.8 and 1.2 Ultrasound indications suspected acute or chronic findings effective at detecting and localizing disruption in tendon operator and user-dependent MRI indications most sensitive imaging modality findings intrasubstance signal and thickening of tendon Treatment Nonoperative activity modification, NSAIDS, and physical therapy indications mainstay of treatment technique rest until pain is improved physical therapy starting with range of motion and progressing to eccentric exercises cortisone injections contraindicated due to risk of quadriceps tendon rupture Operative quadriceps tendon debridement indications very rarely required