Quadriceps tendinitis is an overuse disorder of the quadriceps tendon.

Causes of quadriceps tendinitis
The condition is most commonly seen in athletes and the pain of quadriceps tendinitis is activity-related. The patient usually experiences the pain at the top of the patella.
FORUM DISCUSSIONS
Any advice for Quadriceps tendonitis.
Developing quadriceps tendonitis now after 6 months of no activity, what gives?
Chronic quadriceps tendinopathy.
CLINICAL PUBLICATIONS
Quadriceps tendinopathy: a review—part 1: epidemiology and diagnosis King D, Yakubek G, Chughtai M, Khlopas A, Saluan P, Mont, MA and Genin J. Ann Transl Med. 2019 Feb; 7(4): 71.
Quadriceps tendinopathy: a review, part 2—classification, prognosis, and treatment. King D, Yakubek G, Chughtai M, Khlopas A, Saluan P, Mont MA and Genin J. Ann Transl Med. 2019 Feb; 7(4): 72.