The Anatomy of the Bursa

Small Fluid-Filled Sacs That Allow Your Joints to Move Smoothly

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A bursa is a small, fluid-filled sac within your body that lies near bony prominences and joints. The bursa acts as a cushion between muscles, ligaments, and bones and allows structures to glide and slide past one another with ease and with minimal friction. Injury to a bursa may cause pain, limited motion, and decreased functional mobility. Fun fact: The plural of bursa is bursae.

Anatomy

The bursae in your body are made up of a synovial membrane. This thin membrane of tissue secretes the synovial fluid that is contained within the bursa sac. Synovial fluid is your body’s lubricant, and this viscous fluid inside the bursa allows structures in your body to glide over one another easily. 

Bursae are very small and thin. The average diameter of a bursa in an adult human is about 4 cm, and each bursa is about 2 millimeters thick. The membrane of the bursa is semi-permeable, allowing some materials to flow across the membrane into and out of the sac. An injury to your bursa may cause it to fill with blood or white blood cells.

There are three main types of bursa in your body. These include:

  • Synovial. Synovial bursae are most commonly found and lie near the synovial membrane of the joints of your body.
  • Adventitious. The accidental bursa occur only after continued shearing or repeated pressure over a bony prominence. A bunion is an example of an adventitious bursa.
  • Subcutaneus. These bursae lie between your skin and a bony prominence and allow friction-less motion of your skin over the bone.

There are about 160 bursa in your body, and the main ones can be found in areas of high bony prominence. These bursa include:

  • The pre-patellar bursa. There are about five bursae that surround various areas of your knee joint, providing cushioning.
  • The greater trochanter bursa. There is a large bursa that is located atop the bony prominence of your hip joint. This allows your gluteus medius muscle to glide and slide naturally over the bone.
  • The subacromial bursa. There is a bursa that lies underneath your acromion process of your shoulder. This bursa provides cushioning between that bone and your rotator cuff muscles.
  • The olecranon bursa. This bursa lies between your skin and the bony prominence of your elbow.

If a bursa is surgically excised from your body, it can grow back over a few weeks’ time.

Function

Your bursae serve to reduce friction between your body’s bony prominences and muscles, tendons, and ligaments. They help structures glide and slide past one another while movement occurs. A bursa may also provide a bit of shock absorption; the olecranon bursa in your elbow or your pre-patellar bursa in your knee may help soften a blow to those joints.

Associated Conditions

There are several conditions that may affect your bursae, causing pain, limited movement around a joint, or limited function. These may include:

  • Bursitis. Bursitis occurs when a bursa becomes inflamed. The hallmarks of inflammation include pain, increased tissue temperature, and swelling. When a bursa becomes irritated due to overuse, repetitive strain, or overloading of the tissues around the bursa, it may become painful and swollen. This may make moving the joint near that bursa difficult. Common areas of your body affected by bursitis include the knee, the hip, and the shoulder.
  • Calcification of a bursa. If long-term inflammation and irritation of a bursa occurs, it may cause calcification of that bursa. This most often occurs in the shoulder, and it may lead to calcific bursitis and tendonitis of your shoulder joint. This painful condition causes difficulty moving your arm.
  • Infection. An infection may cause a bursa to become irritated and inflamed. Infection may be due to some local irritant or due to a rheumatic or systemic disease process.

If you suspect you have bursitis, calcification of the bursa, or bursa infection, see your doctor right away. They can be sure to diagnose your condition properly and get you started on the right treatment.

Rehabilitation

If you are having a problem with your bursa around any joint, there are several different treatment options available to help. The treatment you receive depends on your condition.

Medication

If you have an inflamed bursa due to infection, your doctor may prescribe antibiotic medication to treat the problem. The medicine helps to control the infection, which in turn will relieve the pain and limited motion caused by irritation of the bursa.

If you have bursitis, your doctor may prescribe anti-inflammatory medication. Oral steroids may be used, and over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDS) may be effective. If oral steroids and NSAIDS prove ineffective in relieving bursa inflammation, an injection of corticosteroids may be performed, bathing the bursa and surrounding tissue in medicine that fights inflammation.

Physical Therapy

If you have bursitis or limited use of a joint due to a suspected bursa problem, your physician may prescribe physical therapy. Your physical therapist will assess your condition and use various treatment techniques to decrease pain and improve your ability to function.

Treatments that may be used by your physical therapist may include:

  • Exercise. Your therapist may identify impairments that may be leading to an irritated bursa. This may be tight muscles, weakness, or abnormal movement patterns that are placing your bursa in a compromised position. Exercise to improve range of motion (ROM), strength, and functional mobility may be effective in relieving your current problem and preventing future problems with your bursa.
  • Joint mobilization. If tightness around your joint is causing your bursa to become pinched and inflamed, your physical therapist may perform joint mobilizations. These specialized manual movement techniques can help improve the way you move and keep pressure off your inflamed bursa.
  • Ice. If your bursa is inflamed, your therapist may apply ice to your body. The ice has been shown to decrease localized blood flow, helping to calm down the painful inflammation of your bursa. Keep in mind that although ice may feel good and help soothe your pain, it has not been shown to lead to improved outcomes when compared to people who do not use ice for bursitis.
  • Heat. For chronic pain caused by irritation of a bursa, heat may be applied. Heat increases circulation and can bring much-needed oxygen and blood to injured bursa tissues. Use caution; heat may burn your skin, so follow your physical therapist’s directions when using heat. As with ice, using heat for bursitis may feel good, but it has not been shown to offer superior outcomes when compared to people who do not use heat for bursa problems.
  • Ultrasound. Ultrasound is a deep heating treatment occasionally used in physical therapy. When ultrasound is applied to your inflamed bursa, it heats it, leading to increased blood flow which brings in oxygen and washes away inflammatory cells. Keep in mind that ultrasound has not been proven to be more effective than placebo for the treatment of inflammation in the body. Still, you may encounter it in the physical therapy clinic.
  • Electrical stimulation. Your physical therapist may use a modality called electrical stimulation to help treat your bursitis. E-stim, as it is commonly called, may be used to decrease pain and improve muscle function. Another form of e-stim called iontophoresis uses electricity to introduce anti-inflammatory medication into your body.
  • Massage. If tight tissues are causing your bursa to become pinched and inflamed, your physical therapist may use massage techniques to help relieve the tension. Massage can improve blood flow, decrease pain, and improve the way your body moves.

Any treatment offered by your physical therapist should be augmented by specific exercises to help your condition. You should be empowered to learn to self-manage your condition with an appropriate home exercise program, and your therapist should show you techniques to prevent future problems once your bursitis has been effectively eliminated.

Most problems with a bursa can be successfully treated with conservative measures. Bursitis and other related conditions typically last for four to six weeks. If your condition lasts longer, you may need to follow up with your doctor to discuss more invasive treatments.

Surgery

For the most severe cases of bursitis and conditions affecting your bursa, surgery may be performed. During the surgery, called a bursectomy, the injured or inflamed bursa may be surgically excised from the area around your joint. This removal of the damaged and inflamed bursa helps to decrease pain and relieve compression of the bursa. Keep in mind that a new bursa will grow back within a few weeks. This new bursa will not be inflamed or calcified. Working with a physical therapist and performing exercises to minimize stress on your bursa after surgery may be effective in preventing future problems with your bursa.

Many of us take pain-free movement for granted, but when pain strikes and limits your ability to move properly, you should see your physician to determine the cause of your problem and to get back to normal. If irritation of a bursa is the cause, there are several treatments that can quickly and effectively help you return to full mobility. Understanding how these small fluid-filled sacs function can help you be an informed healthcare consumer if a problem with a bursa arises.

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Article Sources

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