Category Archives: Areas of Expertise

Hip Arthroscopy

Hip Arthroscopy

Hip arthroscopy is a surgical procedure that allows doctors to view the hip joint without making a large incision (cut) through the skin and other soft tissues. Arthroscopy is used to diagnose and treat a wide range of hip problems.During hip arthroscopy, your surgeon inserts a small camera, called an arthroscope, into your hip joint. The camera displays pictures on a video monitor, and your surgeon uses these images to guide miniature surgical instruments.

Because the arthroscope and surgical instruments are thin, your surgeon can use very small incisions, rather than the larger incision needed for open surgery. This results in less pain for patients, less joint stiffness, and often shortens the time it takes to recover and return to favorite activities.

Hip arthroscopy has been performed for many years, but is not as common as knee or shoulder arthroscopy.


The hip is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone. The ball is the femoral head, which is the upper end of the femur (thighbone).

A slippery tissue called articular cartilage covers the surface of the ball and the socket. It creates a smooth, frictionless surface that helps the bones glide easily across each other.

The acetabulum is ringed by strong fibrocartilage called the labrum. The labrum forms a gasket around the socket.

The joint is surrounded by bands of tissue called ligaments. They form a capsule that holds the joint together. The undersurface of the capsule is lined by a thin membrane called the synovium. It produces synovial fluid that lubricates the hip joint.

Normal hip anatomy

When Hip Arthroscopy Is Recommended

Your doctor may recommend hip arthroscopy if you have a painful condition that does not respond to nonsurgical treatment. Nonsurgical treatment includes rest, physical therapy, and medications or injections that can reduce inflammation.

Hip arthroscopy may relieve painful symptoms of many problems that damage the labrum, articular cartilage, or other soft tissues surrounding the joint. Although this damage can result from an injury, other orthopaedic conditions can lead to these problems, including:

  • Femoroacetabular impingement (FAI) is a disorder in which extra bone develops along the acetabulum (pincer impingement) or on the femoral head (cam impingement). This bone overgrowth—called spurs—damages the soft tissues of the hip during movement. Sometimes bone spurs develop in both the acetabulum and femoral head.
  • Dysplasia is a condition in which the hip socket is abnormally shallow. This puts more stress on the labrum to keep the femoral head within the socket, and makes the labrum more susceptible to tearing.
  • Snapping hip syndromes cause a tendon to rub across the outside of the joint. This type of snapping or popping is often harmless and does not need treatment. In some cases, however, the tendon is damaged from the repeated rubbing.
  • Synovitis causes the tissues that surround the joint to become inflamed.
  • Loose bodies are fragments of bone or cartilage that become loose and move around within the joint.
  • Hip joint infection

types of femoroacetabular impingement

Stem Cell Therapy

Stem Cell Therapy

A Modern Day Solution for Joint Pain and Injuries. 

If you suffer from joint pain or have soft tissue injuries, your own stem cells

may be the answer.

Stem Cell Therapy offers a viable alternative for individuals who are suffering from joint pain, or who may be considering joint replacement due to injury or arthritis. Patients avoid the lengthy periods of downtime, and extensive rehabilitation that typically follow invasive surgeries.

Stem Cell Therapy and Regenerative Medicine are treatment options that may promote repair of bone, tendon, muscle, ligament, and cartilage (arthritic joints). Using your own adult stem cells may help heal your tissue.

Stem cells can be obtained by harvesting bone marrow with a minimally invasive technique. The stem cells are injected at the site of damaged tissue. This procedure may benefit patients with arthritic joints, bone that has not healed (nonunion), or soft tissue problems such as Achilles tendinitis or ruptures, plantar fasciitis, rotator cuff disease, tennis elbow, and other conditions.

Platelet Rich Plasma (PRP) is another injection technique that may help heal damaged tissue. PRP is obtained from blood drawn from the patient, and concentrated by a centrifugation process. PRP is believed to provide a high concentration of protein growth factors that could be beneficial for healing of acute or chronic soft tissue injuries. This includes Achilles tendinitis, patellar tendinitis, plantar fasciitis, muscle strains, rotator cuff tears, and other conditions.

Please call 727-446-5993 ext. 137 today to schedule an evaluation with Richard V. Abdo, M.D., board certified orthopaedic surgeon, to see if this may be a solution for you.



A bunion is a prominence at the base of the great toe that leads to shoe wear difficulty, pain and swelling. The deformity is caused by the 1st metatarsal (the long bone in the foot) spread inward and the great toe turned outward toward the 2nd toe. Other toe deformities may occur as a result of the abnormal position of the great toe.

There are many causes for the development of a bunion. Heredity plays a role. Some people are born with a foot shape that can lead to a bunion. Shoes that are tight and constrictive often accelerate the formation of a bunion. An estimated 85% of bunions occur in women. A bunion may lead to great toe arthritis over time.

The diagnosis of a bunion is based on examination and X-ray evaluation. There are various types of bunion deformities, and treatment is based on the type of deformity. The primary treatment option is to alter shoe wear. Wear shoes that do not cramp the forefoot. Prescription shoes or orthotics may help. Bunion pads are available, but may be too bulky to fit in shoes.

Surgery can correct painful bunions. There are several surgical procedures depending on the severity of the deformity. Most involve realigning a bone to achieve correction. Surgery is performed as an outpatient with a nerve block and sedation.

If you have questions, or would like an evaluation, please call 727-446-5993 (ext. 110) to make an appointment with Richard V. Abdo, M.D.

Bunion leftBunion Right





Anterior Approach Total Hip Replacement (THR)

Hip replacement is a common surgical procedure to relieve pain, improve motion, and provide better quality of life for patients suffering from advanced arthritis of the hip. Arthritis is wear and tear degeneration and thinning of the protective joint lining called cartilage. The symptoms of arthritis can usually be controlled with non-surgical treatment that includes medication, physical therapy, modifying activity, and injections including cortisone, platelet rich plasma (PRP) and stem cell therapy.

Hip replacement is indicated when the symptoms have become disabling, and are not responding to non-surgical treatment. There are several surgical approaches for THR. Although anterior approach THR is not new, it is gaining in popularity because of the potential benefits, and improved instruments and equipment. An anterior THR is performed through a small incision in the front of the hip. The technique is tissue sparing because it does not detach muscles.

 The potential benefits include:

  • Accelerated recovery because muscles are not detached.
  • Fewer restrictions during recovery.
  • Improved stability of the implants.
  • Decreased hospital stay.
  • Decreased dislocation rate

If you would like more information, or would like to make an appointment, please call 727-446-5993 (x 110).

Anterior approach Total Hip Replacement

Total Ankle Replacement (TAR)

Total ankle replacement (TAR) is a surgical procedure to provide pain relief for patients with arthritis of the ankle joint.

Arthritis is wear and tear degeneration and thinning of the joint cartilage that causes pain, stiffness, and, sometimes, deformity. Arthritis may result from osteoarthritis, past trauma, instability, rheumatoid arthritis, and other conditions.

TAR replaces the joint surfaces with metal and plastic components similar to total hip and knee replacements. This provides pain relief and preserves some motion.

In preparation for a TAR, a preoperative CT scan is performed with a special protocol to define the individual patient’s ankle anatomy and alignment. This allows sterile custom molds to be made that are used during surgery to provide precise position and alignment of the implants. This patient specific precision is believed to allow better function and longevity of the total ankle replacement.

Ankle fusion is another surgical option for pain relief, but stiffens the ankle, putting increased stress on nearby joints. For mild cases, outpatient ankle arthroscopy may provide temporary relief.

Non-surgical treatment for ankle arthritis includes anti-inflammatory medication, ice, braces, physical therapy, cortisone injection, platelet rich plasma injections, or stem cell therapy. TAR is considered when non-surgical treatment no longer helps relieve pain.

An orthopaedic foot and ankle surgeon should be seen for management of ankle arthritis, and to determine if ankle replacement is an option.

If you would like more information, or would like to make an appointment with Richard V. Abdo, M.D., please call 727-446-5993 ext 110.


The Hand

Anthony Marcotte, D.O. is our Hand Specialist at Orthopaedic Specialties

Arthritis of the Hand

The hand and wrist have multiple small joints that work together to produce motion. This gives the fine motion needed to thread a needle or tie a shoelace. When the joints are affected by arthritis, activities of daily living can be difficult. Arthritis can occur in multiple areas of the hand and wrist. It can have multiple causes.

It is estimated that one out of every five people living in the United States has at least one joint with signs or symptoms of arthritis. About half of arthritis sufferers are under age 50. Arthritis is the leading cause of disability in the United States. It typically occurs from either disease or trauma. The exact number of people with arthritis in the hand and wrist is not known.


Cartilage works as nature’s “shock absorber.” It provides a smooth gliding surface for the joint. All arthritic joints lose cartilage. When the cartilage becomes worn or damaged, or is lost due to disease or trauma, the joint no longer has a painless, mobile area of motion.

The body attempts to make up for the lost cartilage. It produces fluid in the joint lining (synovium), which tries to act like a cushion, like water in a waterbed. But it also causes the joint to swell. This restricts motion. The swelling causes stretching of the joint covering (capsule), which causes pain.

Over time, if the arthritis is not treated, the bones that make up the joint can lose their normal shape. This causes more pain and further limits motion.


When arthritis occurs due to disease, the onset of symptoms is gradual and the cartilage decreases slowly. The two most common forms of arthritis from disease are osteoarthritis and rheumatoid arthritis. Osteoarthritis is much more common and generally affects older people. It appears in a predictable pattern in certain joints. Rheumatoid arthritis has other system-wide symptoms and may be passed from parent to child (genetically).


Fractures within the finger joints
Fractures within the finger joints.

When arthritis is due to trauma, the cartilage is damaged. People of any age can be affected. Fractures, particularly those that damage the joint surface, and dislocations are the most common injuries that lead to arthritis. An injured joint is about seven times more likely to become arthritic, even if the injury is properly treated.

Arthritis does not have to result in a painful or sedentary life. It is important to seek help early so that treatment can begin and you can return to doing what matters most to you.


Bone scans of the hands.
Bone scans of the hands.

A doctor can diagnose arthritis of the hand by examining the hand and by taking X-rays. Specialized studies, such as magnetic resonance imaging (MRI), are usually not needed. Sometimes a bone scan is helpful. A bone scan may help the doctor diagnose arthritis when it is in an early stage, even if X-rays look normal.

Arthroscopy pictures of the wrist joint
Arthroscopy pictures of the wrist joint. The white objects are some of the wrist bones as seen through the arthroscope. The metal rod is an arthroscopic probe with a tip measuring 2 mm. It can be seen moving between two of the wrist bones that have a ligament tear between them. Normally, the bones are close together and cannot be moved apart.

Arthroscopy is another way to look at the joint by direct inspection. During an arthroscopic procedure, the surgeon inserts a small camera into the joint to look inside. It provides the clearest picture of the joint without having to make a large incision. However, this is an invasive procedure and should not be used as a routine diagnostic tool.



Early symptoms of arthritis of the hand include joint pain that may feel “dull,” or a “burning” sensation. The pain often occurs after periods of increased joint use, such as heavy gripping or grasping. The pain may not be present immediately, but may show up hours later or even the following day. Morning pain and stiffness are typical.

As the cartilage wears away and there is less material to provide shock absorption, the symptoms occur even with less use. In advanced disease, the joint pain may wake you up at night.

Pain might be made worse with use and relieved by rest. Many people with arthritis complain of increased joint pain with rainy weather. Activities that once were easy, such as opening a jar or starting the car, become difficult due to pain. To prevent pain at the arthritic joint, you might adapt the way you use your hand.


Arthroscopy pictures of the wrist joint
Thumb extension deformity. This patient has lost mobility at the base of the thumb due to arthritis. The next joint closer to the tip of the thumb has become more mobile than normal to make up for the arthritic joint. Normally, the thumb does not come to a right angle with the rest of the hand.
When the affected joint is subject to greater stress than it can bear, it may swell in an attempt prevent further joint use.

Changes in Surrounding Joints

In patients with advanced thumb base arthritis, the neighboring joints may become more mobile than normal.


The arthritic joint may feel warm to touch. This is due to the body’s inflammatory response.

Crepitation and Looseness

There may be a sensation of grating or grinding in the affected joint (crepitation). This is caused by damaged cartilage surfaces rubbing against one another. If arthritis is due to damaged ligaments, the support structures of the joint may be unstable or “loose.” In advanced cases, the joint may appear larger than normal (hypertrophic). This is usually due to a combination of bone changes, loss of cartilage, and joint swelling.


Mucous cyst of the index finger.
Mucous cyst of the index finger.

When arthritis affects the end joints of the fingers (DIP joints), small cysts (mucous cysts) may develop. The cysts may then cause ridging or dents in the nail plate of the affected finger.


Nonsurgical Treatment

Treatment options for arthritis of the hand and wrist include medication, splinting, injections, and surgery.

  • How far the arthritis has progressed
  • How many joints are involved
  • Your age, activity level and other medical conditions
  • If the dominant or non-dominant hand is affected
  • Your personal goals, home support structure, and ability to understand the treatment and comply with a therapy program


Medications treat symptoms but cannot restore joint cartilage or reverse joint damage. The most common medications for arthritis are anti-inflammatories, which stop the body from producing chemicals that cause joint swelling and pain. Examples of anti-inflammatory drugs include over-the-counter medications such as Tylenol and Advil and prescription drugs such as Celebrex.

Glucosamine and chondroitin are widely advertised dietary supplements or “neutraceuticals.” Neutraceuticals are not drugs. Rather, they are compounds that are the “building blocks” of cartilage. They were originally used by veterinarians to treat arthritic hips in dogs. However, neutraceuticals have not yet been studied as a treatment of hand and wrist arthritis. (Note: The U.S. Food and Drug Administration does not test dietary supplements. These compounds may cause negative interactions with other medications. Always consult your doctor before taking dietary supplements)


When first-line treatment with anti-inflammatory medication is not appropriate, injections may be used. These typically contain a long-acting anesthetic, similar to novacaine but longer lasting, and a steroid that can provide pain relief for weeks to months. The injections can be repeated, but only a limited number of times, due to possible side effects, such as lightening of the skin, weakening of the tendons and ligaments and infection.


Injections are usually combined with splinting of the affected joint. The splint helps support the affected joint to ease the stress placed on it by activities. Splints are typically worn during periods when the joints hurt. They should be small enough to allow functional use of the hand when they are worn. Wearing the splint for too long can lead to muscle wasting (atrophy). Muscles can assist in stabilizing injured joints, so atrophy should be prevented.

Surgical Treatment

If nonsurgical treatment fails to give relief, surgery is usually discussed. There are many surgical options. The option chosen should be one that has a reasonable chance of providing long-term pain relief and return to function. It should be tailored to your individual needs. It is important that the treating physician is well versed in current surgical techniques.

Thumb base fusion using a plate and screws.
Thumb base fusion using a plate and screws.

If there is any way the joint can be preserved or reconstructed, this option is usually chosen.
When the damage has progressed to a point that the surfaces will no longer work, a joint replacement or a fusion (arthrodesis) is performed.

Finger joint prosthesis.
Finger joint prosthesis.

Joint fusions provide pain relief but stop joint motion. The fused joint no longer moves; the damaged joint surfaces are gone, so they cannot cause symptoms.

Joint replacement attempt to provide pain relief and functional joint motion. As with hip and knee replacements, there have been significant improvements in joint replacements in the hand and wrist. The replacement joints are made of materials similar to those used in weightbearing joints, such as ceramics or long-wearing metal and plastic parts. The goal is to improve the function and longevity of the replaced joint. Most of the major joints of the hand and wrist can be replaced. A surgeon often needs additional training to perform the surgery. As with any evolving technology, the long-term results of the hand or wrist joint replacements are not yet known. Early results have been promising. Talk with your doctor to find out if these implants are right for you.

After Surgery

After any type of joint reconstruction surgery, there is a period of recovery. Often, you will be referred to a trained hand therapist, who can help you maximize your recovery. You may need to use a postoperative splint or cast for awhile after surgery. This helps protect the hand while it heals.
During this postoperative period, you may need to modify activities to let the joint reconstruction heal properly. Typically, pain medication you take by mouth is also used to reduce discomfort. It is important to discuss your pain with your doctor so it can be adequately treated.

Length of recovery time varies widely and depends on the extent of the surgery performed and multiple individual factors. However, people usually can return to most if not all of their desired activities in about three months after most major joint reconstructions.

Research on the Horizon

Increasingly, doctors are focusing on how to preserve the damaged joint. This includes getting an earlier diagnosis and repairing joint components before the entire surface becomes damaged.

Arthroscopy of the small joints of the hand and wrist is now possible because the equipment has been made much smaller.

There have been encouraging results in cartilage repair and replacement in the larger joints such as the knee, and some of these techniques have been applied to the smaller joints of the hand and arm.

The Neck

Neck Pain

The neck (cervical spine) is composed of vertebrae that begin in the upper torso and end at the base of the skull. The bony vertebrae along with the ligaments (which are comparable to thick rubber bands) provide stability to the spine. The muscles allow for support and motion. The neck has a significant amount of motion and supports the weight of the head. However, because it is less protected than the rest of the spine, the neck can be vulnerable to injury and disorders that produce pain and restrict motion. For many people, neck pain is a temporary condition that disappears with time. Others need medical diagnosis and treatment to relieve their symptoms.


Neck pain may result from abnormalities in the soft tissues—the muscles, ligaments, and nerves—as well as in bones and joints of the spine. The most common causes of neck pain are soft-tissue abnormalities due to injury or prolonged wear and tear. In rare instances, infection or tumors may cause neck pain. In some people, neck problems may be the source of pain in the upper back, shoulders, or arms.

Inflammatory Diseases

The vertebral column
The vertebral column.
Rheumatoid arthritis can destroy joints in the neck and cause severe stiffness and pain. Rheumatoid arthritis typically occurs in the upper neck area.

Cervical Disk Degeneration (Spondylosis)

The disk acts as a shock absorber between the bones in the neck. In cervical disk degeneration (which typically occurs in people age 40 years and older), the normal gelatin-like center of the disk degenerates and the space between the vertebrae narrows. As the disk space narrows, added stress is applied to the joints of the spine causing further wear and degenerative disease. The cervical disk may also protrude and put pressure on the spinal cord or nerve roots when the rim of the disk weakens. This is known as a herniated cervical disk.


Because the neck is so flexible and because it supports the head, it is extremely vulnerable to injury. Motor vehicle or diving accidents, contact sports, and falls may result in neck injury. The regular use of safety belts in motor vehicles can help to prevent or minimize neck injury. A “rear end” automobile collision may result in hyperextension, a backward motion of the neck beyond normal limits, or hyperflexion, a forward motion of the neck beyond normal limits. The most common neck injuries involve the soft tissues: the muscles and ligaments. Severe neck injuries with a fracture or dislocation of the neck may damage the spinal cord and cause paralysis.

Other Causes

Less common causes of neck pain include tumors, infections, or congenital abnormalities of the vertebrae.

When Should You Seek Medical Care?

If severe neck pain occurs following an injury (motor vehicle accident, diving accident, or fall), a trained professional, such as a paramedic, should immobilize the patient to avoid the risk of further injury and possible paralysis. Medical care should be sought immediately.
Immediate medical care should also be sought when an injury causes pain in the neck that radiates down the arms and legs.

Radiating pain or numbness in your arms or legs causing weakness in the arms or legs without significant neck pain should also be evaluated.

If there has not been an injury, you should seek medical care when neck pain is:

  • continuous and persistent
  • severe
  • accompanied by pain that radiates down the arms or legs
  • accompanied by headaches, numbness, tingling, or weakness

Many patients seek orthopaedic care for neck pain because orthopaedists are specifically trained to diagnose, treat, and help prevent problems involving the muscles, bones, joints, ligaments, and tendons. Although some orthopaedists confine their practices to specific areas of the musculoskeletal system, most treat a wide variety of diseases, injuries, and other conditions, including neck pain.

The Spine

The spine, one of the most important of the structures in the body, allows a person to keep upright, stand, move about freely and bend. It also protects the spinal cord, which is made of millions of nerve fibers that connect the brain with the rest of the body.

Spinal Sections
The spinal column is divided into three main sections: the cervical (upper) spine, the thoracic (middle) spine, and the lumbar (lower) spine.

Cervical (Upper) Spine: This segment of the spinal column is made up of the first 7 vertebrae in the spine. It starts just below the skull at the top of the neck and ends just above the mid-back area. It is the most mobile section of the spine. The nerves of the cervical spine branch off to the upper chest and the arms.

Thoracic (Middle) Spine: This segment of the spinal column, the middle part of the back, consists of 12 vertebrae that connect the ribs and form the part of the back wall of the ribcage area between the neck and the diaphragm. This part of the spine and body is structured in a way that limits the amount of spinal movement compared to the cervical or lumbar segments of the spine. The nerves of the thoracic spine branch off to the chest and abdomen.

Lumbar (Lower) Spine: This segment of the spinal column is often called the lower back. It usually consists of five vertebrae. At the base of the lumbar spine is the sacrum, a fusion of many bones that connects the spine to the pelvis. Sometimes one of the bones of the sacrum will form as a separate vertebra rather than being part of the sacrum. This sixth, or transitional, vertebra that some people have in their lumbar spine normally does not cause any problems. Because the lumbar spine is connected to the pelvis where most weight bearing and body movement takes place, some people seem more prone to lower back pain. The nerves of the lumbar spine region branch off to the legs, pelvis, bowel and bladder.

Parts of the Spine
The individual parts of the spine make it a complex mechanism. The spine consists of bones, called vertebrae, and ligaments and muscles that connect the bones to form the spinal column. Other structures of the spine include the intervertebral discs, facet joints, spinal cord, nerve roots, neural foraminae, paraspinal muscles and spinal segments.

The vertebrae are the 24 individual bones of the spine. The body of each vertebra is a large, round portion of bone, and each vertebra is attached to a bony ring. In essence, the vertebrae are stacked on top of each other, and their rings create a hollow tube to hold and protect the spinal cord.

Intervertebral Discs
Intervertebral discs are soft, gel-like cushions between the vertebrae. These discs absorb pressure and help keep the bones of the vertebrae from rubbing against each other.

Facet Joints
The joints of the spine, the facet joints, connect the vertebrae to each other and give the spine its flexibility. The two facet joints of each vertebra (one on each side) overlap with neighboring vertebra’s facet joints. Without these joints, the spine would not be able to bend or twist.

Spinal Cord and Nerve Roots
The spinal cord is a column of millions of nerve fibers that carry messages from the brain to the rest of the body. The nerves control the body’s organs and parts, and allow a person to control his or her muscles.

The nerve fibers of the spinal cord branch off in pairs, called nerve roots, at different places in the spine to connect to specific parts of the body. The nerves of the cervical spine go to and control the upper chest and the arms. The nerves of the thoracic spine go to and control the chest and abdomen. The nerves of the lumbar spine go to and control the legs, pelvis, bowel and bladder. Damage to the spinal cord can cause paralysis in certain areas of the body and not in others, depending on which nerve roots are affected.

Neural Foraminae
The neural foraminae are the small openings on each side of the vertebrae where the pairs of nerve roots exit the spinal column to connect to specific areas of the body.

Paraspinal Muscles
Paraspinal muscles are the many muscles next to the spine. They support the spine and cause the spine to move. Each muscle controls some part of the movement between the vertebrae and the rest of the body.

Spinal Segments
A spinal segment is a term given to an individual grouping of parts of the spine. One spinal segment consists of two vertebrae attached by ligaments, the disc between the vertebrae, the facet joints that connect the two vertebrae and the neural foraminae between the two vertebrae.

The Shoulder

The shoulder is one of the most flexible of the body’s joints. The shoulder joint is what allows people to move their arms and, as a result, move their hands to where they need to be used. To be so flexible, the shoulder must have a wide range of movement. Unfortunately, this ability to move so freely means the shoulder joint is one of the less stable joints in the body.

The shoulder is a ball and socket joint. However, unlike other ball and socket joints in the body where the ball is nearly surrounded by the bone “cup” part of the joint, the ball end of the upper arm bone (humerus) instead rests in a shallow cup located on the end of the shoulder blade (scapula). A cuff of cartilage (labrum) forms an extended cup in which the ball end of the arm bone rests.

The entire shoulder joint is held in place by a complex arrangement of muscles, tendons and ligaments.

Some of these muscles and tendons form the shoulder’s rotator cuff, a group of four tendons and four muscles that work together and form a “cuff” over the upper end of the arm. The four muscles are the subscapularis, the supraspinatus, the infraspinatus and the teres minor. The muscles start on the shoulder blade (scapula) and are connected to the upper part of the arm bone (humerus) by the tendons that are attached directly into the bone. The rotator cuff helps a person raise and rotate the arm and stabilize the shoulder within the joint.

In addition, the shoulder joint has a subacromial bursa, a fluid-filled cushioning sac between the deltoid muscle, the curved section of bone that forms the top of the shoulder (acromion) and the rotator cuff.

When one of the elements of this complex joint is injured, worn down by overuse or simply out of balance, the result usually is shoulder pain.