Kneeling and bursitis
A bursa is a lubricated pouch or sac in regions where there is a lot of movement between muscles and bone.
If uncommon pressure is repeatedly put onto the area of a bursa - what we call 'overuse' then the lining of the bursa may become inflamed. Two of the most common types of knee bursitis are 'clergyman's knee' and 'housemaid's knee', both from excessive kneeling, but in different body positions.