A bursa is a closed fluid-filled sac that functions as a
gliding surface to reduce friction between tissues of the
body. "Bursae" is plural for "bursa." The major bursae
are located adjacent to the tendons near the large joints,
such as the shoulders, elbows, hips, and knees.
Including minor bursae, there are more than 150 in the
human body. When the bursa becomes inflamed and
tender, the condition is known as “bursitis”. There are
several major bursae (some are shown here) and many
minor bursae. The cause of bursitis may be chronic
overuse, trauma, rheumatoid arthritis, gout, infection, or
unknown. Bursitis commonly occurs in the shoulder,
knee (washmaid’s knee), elbow, and hip. Other areas
affected include the Achilles tendon and the foot.
Chronic inflammation can occur with repeated attacks
of bursitis or injuries and eventually calcium deposits
may be seen in bursae.  These calcium deposits cause
extreme pain on movement of the muscles and may
actually entrap tendons.  Pain on movement is the most
common symptom with limitation in the range of motion
being common.  Some bursitis causes substantial pain
occurring at night preventing sleep.

Trochanteric bursitis: Inflammation of the bursa
located over the lateral thigh resulting in awakening from
sleep with deep lateral thigh pain (on the outside part of
the thigh) and pain after prolonged walking.  The pain is
usually most intense over the upper lateral thigh and
refers to the outside of the lower thigh and sometimes
into the knee.  Causes include repetitive stress
(overuse) injuries, multiple minor traumatic injuries,
lumbar spine disease such as scoliosis, leg-length
inequalities, rheumatoid arthritis, lying on one side of
the body for an extended period (perhaps due to
another injury or illness), excessive or prolonged
pressure on the hip such as from standing too long, an
acute traumatic incident such as a fall, and previous
surgery or prosthetic implants in the hip.  Symptoms:
Aching pain is usually focused on the outside of the
upper thigh, just over the point of the hip. Pain may
radiate down the outside of the thigh as far as the knee.
Pain is worse when you lie down or roll over on the
affected side. Climbing stairs, sitting or standing too
long and walking may all be painful. Pain at night is
common and may make sleeping difficult.  Diagnosis is
made on clinical grounds and with diagnostic injections.  
Therapy is usually diagnostic injections and exercises
but rarely surgical excision of the bursa is required.

Knee Bursitis:      
The knee has three areas that are involved in bursitis:  
Prepatellar bursa (area 1) which causes pain on bending
the knees or resting on the knees.  Infrapatellar bursa
(area 2) which is involved with jumping injuries.  
Anserine bursa (area 3) which occurs due to aging and
gives pain from the knee joint down the inside of the leg.
Treatment is through physical therapy and injections.

Olecranon Bursitis
Olecranon bursitis may follow a traumatic accident,
such as a fall onto the back of the elbow, or it may
seemingly pop up out of nowhere. People who rest their
elbows on hard surfaces may aggravate the condition
and make the swelling more prominent.  Occasionally,
the swelling and inflammation can be the result of an
infection within the bursa, this is called infected bursitis.
Patients with systemic inflammatory conditions, such as
gout and rheumatoid arthritis, are also at increased risk
of developing this condition. Treatment for routine
olecranon bursitis is usually best accomplished by
draining the fluid from the sac. Often steroid injections
into the bursa will be performed after draining the fluid.
Steroids will suppress the inflammatory response to
increase the chance of a lasting solution. An oral anti-
inflammatory medication is also commonly prescribed.
If there is a question of infection within the bursa, the
fluid will be sent for analysis. Treatment of infected
bursitis requires repeated drainage of the fluid,
antibiotic treatment, and sometimes a surgical
procedure to remove the infected bursa. Signs of
infection include fevers, chills, redness around the
bursa, and suspicious fluid within the bursa.

Ischial Bursitis
Other important bursae are the ischial bursa which
causes deep aching pain in the buttocks when sitting.
The ischial bursa lies between the ischial tuberosity and
the overlying gluteus maximus muscle.
Inflammation commonly arises as a result of trauma or
prolonged sitting on a hard surface (weaver bottom).
Pain may radiate down the back of the thigh and mimic
sciatic nerve inflammation; however, it can be
reproduced by pressure over the ischial tuberosity
which lies deep in the buttocks.  Injection therapy with
steroids can be helpful in its management.  

Calcaneal bursitis (Heel)
Two bursae are found at the level of insertion of the
Achilles tendon; one is deep to the tendon and one is
superficial. The (superficial) posterior calcaneal bursa
can become inflamed primarily in patients with painful
heel spurs, a history of improper shoes (eg, high heels),
or prolonged walking. Inflammation can occur
secondarily from Achilles tendonitis. This bursitis often
results from overuse in young athletes.
The (deep) retrocalcaneal bursa rarely is a problem.
Patients complain of pain on movement and tenderness
immediately anterior to the Achilles tendon. Treatment
is through physical therapy and steroid injections.

Click Pic
Knee Bursae Locations
(3) and Knee Bursitis
(click to enlarge)
Olecranon (elbow)
Non Infected Bursitis
Infected Bursitis of
The Elbow
Ischial Bursae
Click to