Bursae are fluid filled sacs that are present around the various joints in the body. These bursae reduce the friction during use of the joint. They also protect the joint from any injury as they act as a cushion which absorbs the direct impact of the injury to the joint.
Knee joint is an important joint of the body and is one of the weight bearing joints of the body. There are 13 bursae around the knee joint. Out of these, 3 main bursae present around the joint are semimembranosus bursa, prepatellar bursa and infrapatellar bursa. Inflammation of any of the bursa is called as bursitis. Any injury to the bursa, repeated stress, or knee surgeries can give rise to bursitis.
In bursitis, there is swelling of the bursa. The swelling is due to inflammation of the bursa. Sometimes, if injury is the cause, capillaries burst and blood accumulates in the bursa and the bursa enlarges in size. Other causes are diseases such as rheumatoid arthritis, osteoarthritis, gout and infection.
A large swelling is seen over the location of the bursa. Initially the swelling is painless, gradually with more friction and movements, it becomes painful in nature.
In semimembranosus bursitis, the lump is present over the posterior and medial aspect of the knee. It becomes more noticeable when the leg is made straight and becomes less prominent when the knee is flexed. The prepatellar bursitis is the inflammation of the prepatellar bursa that is situated in front of the patella bone.
Constant friction between the patella and ground in miners, carpet layers or housemaids usually gives rise to this condition. The swelling is present exactly in front of the knee joint. It is also called as housemaid’s knee.
The infrapatellar bursa is situated little below the patella. Chronic inflammation of this bursa gives rise to the infrapatellar bursitis. If there is only swelling, then treatment is not required as this condition regresses on its own.
Sometimes, the swelling becomes large and painful. In such cases, the fluid in it needs to be aspirated or in some rare cases, surgery is required to excise the whole bursa. Recurrences are common, so proper treatment is necessary.