This patient has patellofemoral pain syndrome. Patellofemoral pain syndrome is of unclear etiology but is likely due to several different factors that affect the load distribution underneath the patella, such as deconditioning and patellofemoral malalignment. It is characterized by anterior knee pain that is slow in onset and typically made worse with running, climbing stairs, and prolonged sitting. On examination, there is frequently increased patellar laxity with medial and lateral displacement. Additionally, pain may be reproduced when posteriorly directed pressure is applied to the patella. Treatment is often challenging but generally consists of addressing any identified underlying causes (such as deconditioning), activity modification, and physical therapy.

Iliotibial band syndrome can occur from overuse or from alterations in anatomic alignment or biomechanical function. It typically causes lateral knee pain that is worsened by walking down an incline. On examination, there is frequently tenderness to palpation of the lateral femoral epicondyle, which is approximately 2 to 3 cm proximal to the lateral joint line, accompanied by weakness of the hip abductor muscles and the knee extender and flexor muscles. Pain is reproduced when the examiner repeatedly flexes and extends the supine patient's knee while the examiner's thumb is on the lateral femoral epicondyle (positive Noble test).

Pes anserine bursitis is caused by inflammation of the pes anserine bursa, located at the proximal anteromedial tibia. Bursitis usually develops as the result of overuse or constant friction and stress on the bursa. Pes anserine bursitis is common in athletes, particularly runners. Tenderness on the anteromedial aspect of the knee about 4 to 5 cm below the joint line is reproduced by palpation.

Prepatellar bursitis is caused by inflammation of the prepatellar bursa, which overlies the anterior surface of the patella. Patients with prepatellar bursitis present with anterior knee pain and swelling. Possible causes include direct trauma, gout, and infection. On examination, a palpable fluid collection is often present.