What Is a Bursa Sac?

A "bursa" is a flattened sac that acts as a cushion for your bones and muscles. The sacs are filled with fluid and relieve friction where bones and tendons or muscles rub together. A bursa can become inflamed --- bursitis --- if there is too much friction, which can result in a lot of pain and may necessitate a visit to the doctor.

Function

• The bursa sac protects joints from inflammation by reducing the friction caused when they rub against each other. The sac is fluid-filled and lined with synovial membranes. These membranes secrete a protein- and collagen-rich lubricating fluid. Healthy bursae that aren't irritated and function properly will help your joints work painlessly.

Locations

• You can find bursa sacs all over the body wherever there are joints, from the neck all the way down to your toes. The body contains about 160 bursa sacs, although that figure varies according to the individual, as some bursae arise from excess rubbing in an area, causing a sac to form to protect it from trauma. Most bursae are in the shoulders, elbows, hips and knees. The shoulder has the most bursa sacs of any joint in the body, with eight.

Bursitis

• Sometimes, the friction between a bone and a tendon or muscle rubbing together is so great that it causes excess fluid to build up, leading to inflammation and a condition known as bursitis. This can happen due to an injury, stress or pressure to the bone over an extended period of time, causing foreign fluids and blood to enter the bursa sac.

Treatment

• If you've developed inflammation of bursae and it appears to be infected, see a doctor, who may be able to solve the problem with antibiotics. If that doesn't work, you may need to have the bursae drained. You might be able to treat less severe cases at home with cold therapy or ultrasound therapy.