
Long periods pressing on the infrapatellar bursa may cause it to become inflamed.
Clergyman's knee is a swelling below the knee, properly called infrapatellar bursitis - inflammation in the infrapatellar bursa. Page updated June 2024 by Dr Sheila Strover (Clinical Editor)

Long periods pressing on the infrapatellar bursa may cause it to become inflamed.
Because the knee has a wide range of movement, several bursa exist in relation to this joint, usually closely related to the areas where there is a lot of frictional movement. The infrapatellar bursa is at the front of the knee below the patella.

Illustration of a side view of the knee, which has been cut in half to show the bursae and other spaces and folds that allow the knee's movement.
"....A bursa is a fluid-filled sac meant to reduce the friction between surfaces. A bursa can be superficial when present between the skin and underlying tendon or bone...."
"....Infrapatellar bursae can be superficial or deep. The superficial infrapatellar bursa is located between the tibial tubercle and the overlying skin, whereas the deep infrapatellar bursa is located between the posterior aspect of the patellar tendon and the tibia.....
"....Infrapatellar bursitis is more common in repetitive knee trauma, but sometimes aetiology remains elusive....The bursa with chronic inflammation may have calcification or become a solid lump losing its fluid content....
"....Trauma, infection, overuse, and hemorrhage are some of the common causes for inflammation. Other causes include systemic illness like collagen vascular disease and inflammatory arthropathy....
Surgery may sometimes be necessary if the situation is complicated - such as a very large bursa, calcification or other complication.
"....Open excision can be performed as a one-stage or a two-stage procedure, and endoscopy can be an alternative.....