Semipatellar Bursa

bursa suprapatellaris

The suprapatellar bursa is the largest extension of the knee joint synovial cavity, occupying the space between the quadriceps femoris and the anterior distal femur. It communicates with the main knee joint cavity in nearly all adults (the suprapatellar plica that originally divided them is usually incomplete in adults). Knee joint effusions fill the suprapatellar bursa producing the characteristic suprapatellar swelling visible on examination.

Region: Knee

Biomechanics

Function & Actions

Allows free quadriceps tendon movement over the distal femur during knee flexion; reduces friction between the tendon and bone

Clinical Relevance

Clinical Notes

Suprapatellar bursa effusion produces visible and palpable fullness proximal to the patella between the quadriceps muscle and the femur. Ballottement of the patella (compressing the suprapatellar bursa) is the clinical test for knee effusion. Arthrofibrosis after knee surgery can obliterate the suprapatellar bursa, severely limiting knee flexion and requiring manipulation under anaesthesia or arthroscopic lysis of adhesions.

Pathology

Common Injuries & Conditions

Suprapatellar Bursitis

Bursal inflammation or effusion producing suprapatellar swelling confirmed by patellar ballottement, the clinical correlate of significant knee joint effusion.