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Shoulder Anatomy

The shoulder is the most flexible joint in the body that enables a wide range of movements including forward flexion, abduction, adduction, external rotation, internal rotation, and 360-degree circumduction. Thus, the shoulder joint is considered the most insecure joint of the body, but the support of ligaments, muscles, and tendons function to provide the required stability. 

Bones of the Shoulder

The shoulder joint is a ball and socket joint made up of three bones, namely the humerus, scapula, and clavicle. 

Humerus

The end of the humerus or upper arm bone forms the ball of the shoulder joint. An irregular shallow cavity in the scapula called the glenoid cavity forms the socket for the head of the humerus to fit in. The two bones together form the glenohumeral joint, which is the main joint of the shoulder.

Scapula and Clavicle

The scapula is a flat triangular-shaped bone that forms the shoulder blade. It serves as the site of attachment for most of the muscles that provide movement and stability to the joint. The scapula has four bony processes - acromion, spine, coracoid and glenoid cavity. The acromion and coracoid process serve as places for attachment of the ligaments and tendons. 

The clavicle bone or collarbone is an S-shaped bone that connects the scapula to the sternum or breastbone. It forms two joints: the acromioclavicular joint, where it articulates with the acromion process of the scapula and the sternoclavicular joint where it articulates with the sternum or breast bone. The clavicle also forms a protective covering for important nerves and blood vessels that pass under it from the spine to the arms.

Soft Tissues of the Shoulder 

The ends of all articulating bones are covered by smooth tissue called articular cartilage, which allows the bones to slide over each other without friction, enabling smooth movement. Articular cartilage reduces pressure and acts as a shock absorber during movement of the shoulder bones. Extra stability to the glenohumeral joint is provided by the glenoid labrum, a ring of fibrous cartilage that surrounds the glenoid cavity. The glenoid labrum increases the depth and surface area of the glenoid cavity to provide a more secure fit for the half-spherical head of the humerus.

Ligaments of the Shoulder

Ligaments are thick strands of fibers that connect one bone to another. The ligaments of the shoulder joint include:

Coracoclavicular ligaments: These ligaments connect the collarbone to the shoulder blade at the coracoid process.
Acromioclavicular ligament: This connects the collarbone to the shoulder blade at the acromion process. 
Coracoacromial ligament: It connects the acromion process to the coracoid process. 
Glenohumeral ligaments: A group of 3 ligaments that form a capsule around the shoulder joint and connect the head of the arm bone to the glenoid cavity of the shoulder blade. The capsule forms a watertight sac around the joint. Glenohumeral ligaments play a very important role in providing stability to the otherwise unstable shoulder joint by preventing dislocation.

Muscles of the Shoulder

The rotator cuff is the main group of muscles in the shoulder joint and is comprised of 4 muscles. The rotator cuff forms a sleeve around the humeral head and glenoid cavity, providing additional stability to the shoulder joint while enabling a wide range of mobility. The deltoid muscle forms the outer layer of the rotator cuff and is the largest and strongest muscle of the shoulder joint.

Tendons of the Shoulder

Tendons are strong tissues that join muscle to bone allowing the muscle to control the movement of the bone or joint. Two important groups of tendons in the shoulder joint are the biceps tendons and rotator cuff tendons.

Bicep tendons are the two tendons that join the bicep muscle of the upper arm to the shoulder. They are referred to as the long head and short head of the bicep.

Rotator cuff tendons are a group of four tendons that join the head of the humerus to the deeper muscles of the rotator cuff. These tendons provide more stability and mobility to the shoulder joint.

Nerves of the Shoulder

Nerves carry messages from the brain to muscles to direct movement (motor nerves) and send information about different sensations such as touch, temperature, and pain from the muscles back to the brain (sensory nerves). The nerves of the arm pass through the shoulder joint from the neck. These nerves form a bundle at the region of the shoulder called the brachial plexus. The main nerves of the brachial plexus are the musculocutaneous, axillary, radial, ulnar and median nerves.

Blood vessels of the Shoulder

Blood vessels travel along with the nerves to supply blood to the arms. Oxygenated blood is supplied to the shoulder region by the subclavian artery that runs below the collarbone. As it enters the region of the armpit, it is called the axillary artery and further down the arm, it is called the brachial artery.

The main veins carrying de-oxygenated blood back to the heart for purification include:

Axillary vein: This vein drains into the subclavian vein.

  • Cephalic vein: This vein is found in the upper arm and branches at the elbow into the forearm region. It drains into the axillary vein.
  • Basilic vein: This vein runs opposite the cephalic vein, near the triceps muscle. It drains into the axillary vein.

Shoulder Conditions

  • Arthritis of the Shoulder Arthritis of the Shoulder

    The term arthritis literally means inflammation of a joint but is generally used to describe any condition in which there is damage to the cartilage. Damage of the cartilage in the shoulder joint causes shoulder arthritis. Inflammation is the body's natural response to injury. The warning signs that inflammation presents are redness, swelling, heat, and pain.

  • Rotator Cuff Tear Rotator Cuff Tear

    A rotator cuff is a group of tendons in the shoulder joint that provides support and enables a wide range of motion. A major injury to these tendons may result in rotator cuff tears. It is one of the most common causes of shoulder pain in middle-aged and older individuals.

  • Shoulder Instability Shoulder Instability

    Shoulder instability is a chronic condition that causes frequent dislocation of the shoulder joint.

  • Frozen Shoulder Frozen Shoulder

    Frozen shoulder, also called adhesive capsulitis, is a condition in which you experience pain and stiffness in your shoulder. The symptoms appear slowly, worsen gradually and usually take one to three years to resolve on their own.

  • SLAP Tears SLAP Tears

    The term SLAP (superior –labrum anterior-posterior) lesion or SLAP tear refers to an injury of the superior labrum of the shoulder.

  • Shoulder Impingement Shoulder Impingement

    Shoulder impingement is the inflammation of the tendons of the shoulder joint. It is one of the most common causes of pain in the shoulder. Shoulder impingement is also called swimmer’s shoulder, tennis shoulder or rotator cuff tendinitis.

  • Acromioclavicular (AC) Joint Osteoarthritis Acromioclavicular (AC) Joint Osteoarthritis

    Osteoarthritis also called degenerative joint disease, is the most common form of arthritis. It occurs most often in older people. AC joint osteoarthritis affects the tissue covering the ends of bones (cartilage) in the AC joint of the shoulder. The cartilage becomes damaged and worn out causing pain, swelling, stiffness and restricted movement in the AC joint.

  • Acromioclavicular (AC) Arthritis Acromioclavicular (AC) Arthritis

    The acromioclavicular joint is part of the shoulder joint. It is formed by the union of the acromion, a bony process of the shoulder blade, and the outer end of the collar bone or clavicle. The joint is lined by cartilage that gradually wears with age as well as with repeated overhead or shoulder level activities such as basketball. The condition is referred to as AC arthritis or acromioclavicular arthritis.

  • Shoulder Pain Shoulder Pain

    Pain in the shoulder may suggest an injury, which is more common in athletes participating in sports such as swimming, tennis, pitching, and weightlifting. The injuries are caused due to the over usage or repetitive motion of the arms.

  • Rotator Cuff Pain Rotator Cuff Pain

    Pain in the shoulder may suggest an injury, which is more common in athletes participating in sports such as swimming, tennis, pitching, and weightlifting. The injuries are caused due to the over usage or repetitive motion of the arms.

  • Anterior Shoulder Instability Anterior Shoulder Instability

    Anterior shoulder instability, also known as anterior glenohumeral instability, is a condition in which damage to the soft tissues or bone causes the head of the humerus (upper arm bone) to dislocate or sublux from the glenoid fossa, compromising the function of the shoulder. It is caused by trauma or injury to the glenohumeral joint in which the upper arm bone is dislodged from its usual position in the middle of the glenoid fossa, and there is no longer joint articulation.

  • Posterior Shoulder Instability Posterior Shoulder Instability

    Posterior shoulder instability, also known as posterior glenohumeral instability, is a condition in which the head of the humerus (upper arm bone) dislocates or subluxes posteriorly from the glenoid (socket portion of the shoulder) as a result of significant trauma. A partial dislocation is referred to as a subluxation whereas a complete separation is referred to as a dislocation.

  • Shoulder Labral Tear with Instability Shoulder Labral Tear with Instability

    Shoulder instability results when the humeral head is not held firmly within the glenoid cavity and may lead to a dislocation. Tearing, stretching or peeling of the labrum can result in shoulder instability. It can also occur with defects of the shoulder capsule and ligaments.

  • Shoulder Labral Tear with Instability Shoulder Labral Tear

    The shoulder consists of a ball-and-socket joint formed by the upper end of the humerus (upper arm bone) and a cavity in the shoulder blade called the glenoid. The glenoid cavity is surrounded by a rim of cartilage called the labrum. The labrum adds depth to the cavity making the joint more stable and positions the ball within the socket.

  • Partial Rotator Cuff Tear Partial Rotator Cuff Tear

    A partial rotator cuff tear is an incomplete tear that involves damage to a part of the tendon. The tear can be at the top, bottom or inner side of the tendon and does not go all the way through the tendon completely.

  • Shoulder Fracture Shoulder Fracture

    The shoulder is the most flexible joint in the body, enabling a wide range of movements. It is a ball-and-socket joint made up of three bones, namely the humerus (upper arm bone), scapula (shoulder blade) and clavicle. The head of the humerus articulates with the socket of the scapula called the glenoid cavity. The clavicle bone or collarbone is an S-shaped bone that connects the scapula to the sternum or breastbone.

  • Clavicle Fracture Clavicle Fracture

    The break or fracture of the clavicle (collarbone) is a common sports injury associated with contact sports such as football and martial arts, as well as impact sports such as motor racing. A direct blow over the shoulder that may occur during a fall on an outstretched arm or a motor vehicle accident may cause the clavicle bone to break.

  • Proximal Humerus Fractures Proximal Humerus Fractures

    The humerus is the bone that forms the upper arm. It articulates with the glenoid cavity of the scapula (shoulder blade) to form the shoulder joint and with the lower arm bones – the ulna and radius – to form the elbow joint. The proximal humerus is the upper end of the arm bone that forms the shoulder joint.

  • Bicep Tendon Rupture Bicep Tendon Rupture

    The biceps tendon is a tough band of connective fibrous tissue that attaches your biceps muscle to the bones in your shoulder on one side and the elbow on the other side.

  • Proximal Biceps Tendon Rupture Proximal Biceps Tendon Rupture

    The biceps muscle is the muscle of the upper arm which is necessary for the movement of the shoulder and elbow. It is made of a ‘short head’ and a ‘long head’ which function together. These are connected to the shoulder joint by two tendons called the proximal biceps tendons and to the elbow joint by a single distal biceps tendon.

  • Subacromial Impingement Syndrome Subacromial Impingement Syndrome

    SAIS is the inflammation and irritation of your rotator cuff tendons. This occurs when the tendons rub against the outer end of the shoulder blade (the acromion) while passing through the subacromial space during shoulder movement.

  • Little League Shoulder Little League Shoulder

    Little league shoulder is an injury to the growth plate of the upper arm bone at the shoulder joint of children. It is an overuse injury caused by repeated pitching or throwing, especially in children between the ages of 10 to 15 years. This condition is mostly seen in baseball pitchers, but children in other sports who use improper throwing action are also at risk.

  • Baseball and Shoulder Injuries Baseball and Shoulder Injuries

    Shoulder injuries in baseball players are usually associated with pitching. While this overhand throwing activity can produce great speed and distance for the ball, when performed repeatedly, can place a lot of stress on the shoulder. While pitching, the arm is thrown outward and backward to generate speed.

  • Shoulder Dislocation Shoulder Dislocation

    Sports that involve overhead movements and repeated use of the shoulder at your workplace may lead to sliding of the upper arm bone from the glenoid. The dislocation might be a partial dislocation (subluxation) or a complete dislocation causing pain and shoulder joint instability. The shoulder joint often dislocates in the forward direction (anterior instability), and sometimes in the backward or downward direction.

  • Proximal Biceps Tendinitis Proximal Biceps Tendinitis

    Proximal biceps tendinitis is the irritation and inflammation of the biceps tendon at the shoulder joint. The biceps muscle is the muscle of the upper arm which is necessary for the movement of the shoulder and elbow. It is made of a ‘short head’ and a ‘long head’ which function together. The long head of the biceps tendon is attached at the top of the shoulder joint. The short head is attached to your shoulder blade.

  • Internal Impingement of the Shoulder Internal Impingement of the Shoulder

    Internal shoulder impingement can be described as a pathological condition resulting from repetitive impingement of the internal surface of the rotator cuff by the bones at the back of the glenohumeral joint.

  • Rotator Cuff Re-tear Rotator Cuff Re-tear

    Rotator cuff repair is a surgery to repair an injured or torn rotator cuff. A re-tear may occur a few years after surgery due to multiple reasons including aging, a massive previous tear (more than 5cm), fatty degradation of the tendons, inflammatory arthritis, and inappropriate rehabilitation.

  • Shoulder Tendonitis Shoulder Tendonitis

    Shoulder tendonitis is a condition characterized by inflammation of the tendons which connect the muscles to the shoulder bones. Tendonitis of the rotator cuff tendons is known as rotator cuff tendonitis. If the biceps tendon is affected, the condition is known as bicipital tendonitis.

  • Throwing Injuries of the Shoulder Throwing Injuries of the Shoulder

    Throwing injuries of the shoulder are injuries sustained as a result of trauma by athletes during sports activities that involve repetitive overhand motions of the arm as in baseball, American football, volleyball, rugby, tennis, track and field events, etc. Throwing injuries are mostly seen in the shoulder and elbow and can occur due to improper techniques, training errors, muscle imbalance, and overuse of muscles.

  • Shoulder Disorders Shoulder Disorders

    The shoulder is the most flexible joint in the body that enables a wide range of movements. Aging, trauma or sports activities can cause injuries and disorders that can range from minor sprains or strains to severe shoulder trauma.

  • Multidirectional Instability of the Shoulder Multidirectional Instability of the Shoulder

    The shoulder consists of a ball and socket joint where the rounded end of the humerus (upper arm bone) fits into a socket (glenoid cavity) formed by the shoulder blade. The joint is stabilized by the surrounding capsule, ligaments, and tendons of the rotator cuff muscles. Shoulder instability results when the humerus is not held firmly within the socket and moves away from the glenoid cavity.

Shoulder Procedures

  • Shoulder Joint Replacement Shoulder Joint Replacement

    Total shoulder replacement surgery is performed to relieve symptoms of severe shoulder pain and disability due to arthritis. In this surgery, the damaged articulating parts of the shoulder joint are removed and replaced with artificial prostheses. Replacement of both the humeral head and the socket is called a total shoulder replacement.

  • Reverse Shoulder Replacement Reverse Shoulder Replacement

    Conventional surgical methods such as total shoulder joint replacement are not very effective in the treatment of rotator cuff arthropathy. Reverse total shoulder replacement is an advanced surgical technique specifically designed for rotator cuff tear arthropathy, a condition where you suffer from both shoulder arthritis and a rotator cuff tear.

  • Shoulder Arthroscopy Shoulder Arthroscopy

    Arthroscopy is a minimally invasive diagnostic and surgical procedure performed for joint problems. Shoulder arthroscopy is performed using a pencil-sized instrument called an arthroscope. The arthroscope consists of a light system and camera that projects images of the surgical site onto a computer screen for your doctor to clearly view. Arthroscopy is used to treat disease conditions and injuries involving the bones, cartilage, tendons, ligaments, and muscles of the shoulder joint.

  • Acromioclavicular (AC) Joint Reconstruction Acromioclavicular (AC) Joint Reconstruction

    The acromioclavicular (AC) joint is one of the joints present within your shoulder. It is formed between a bony projection at the top of the shoulder blade (acromion) and the outer end of the clavicle (collarbone). The joint is enclosed by a capsule and supported by ligaments.

  • Rotator Cuff Repair Rotator Cuff Repair

    The rotator cuff is a group of 4 muscles in the shoulder joint including the supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles originate in the scapula and attach to the head of the humerus through tendons. The rotator cuff forms a sleeve around the humeral head and glenoid cavity, providing stability to the shoulder joint while enabling a wide range of movements.

  • SLAP Repair SLAP Repair

    A SLAP repair is an arthroscopic shoulder procedure to treat a specific type of injury to the labrum called a SLAP tear.

  • Revision Shoulder Replacement Revision Shoulder Replacement

    Total shoulder replacement is the replacement of the head of the humerus (upper arm bone) and the glenoid cavity (cavity of the shoulder blade) into which the humerus fits, with artificial prostheses to relieve pain, swelling, and stiffness caused due to damage of cartilage at the articulating surfaces.

  • Minimally Invasive Shoulder Joint Replacement Minimally Invasive Shoulder Joint Replacement

    Shoulder joint replacement is a surgical procedure that replaces damaged bone surfaces with artificial humeral and glenoid components to relieve pain and improve functional ability in the shoulder joint.

  • Sternoclavicular Joint Reconstruction Sternoclavicular Joint Reconstruction

    The sternoclavicular (SC) joint is the joint between the breastbone (sternum) and the collar bone (clavicle). Injuries to this joint are called sternoclavicular joint injuries and can include stretching or tearing of the ligaments. It is usually caused due to severe trauma or a direct blow to the side of your body such as in motor vehicle accidents or contact sports.

  • Shoulder Labrum Reconstruction Shoulder Labrum Reconstruction

    Traumatic injury to the shoulder or overuse of the shoulder by excessive throwing or weightlifting can cause a labral tear. In addition, the aging process may weaken the labrum, leading to injury secondary to wear and tear.

  • Arthroscopic Superior Capsular Reconstruction (SCR) Arthroscopic Superior Capsular Reconstruction (SCR)

    Superior Capsular Reconstruction is a surgical procedure to repair massive, irreparable rotator cuff tears. The surgery involves reconstruction of the superior capsule of the shoulder joint using an autograft (tissue from the same person) or an allograft (tissue from a donor).

  • SC Joint Injury Reconstruction SC Joint Injury Reconstruction

    The sternoclavicular (SC) joint is the joint between the breastbone (sternum) and the collar bone (clavicle). Injuries to this joint are called sternoclavicular joint injuries and can include stretching or tearing of the ligaments. It is usually caused due to severe trauma or a direct blow to the side of your body such as in motor vehicle accidents or contact sports.

  • Bicep Tendon Rupture at Shoulder Bicep Tendon Rupture at Shoulder

    The biceps muscle is present on the front of your upper arm and functions to help you bend and rotate your arm. The biceps tendon is a tough band of connective fibrous tissue that attaches your biceps muscle to the bones in your shoulder on one side and the elbow on the other side.

  • Arthroscopic Frozen Shoulder Release Arthroscopic Frozen Shoulder Release

    An arthroscopic frozen shoulder release is a minimally-invasive shoulder surgery performed to relieve pain and restore normal function using a special instrument called an “arthroscope”.

  • Shoulder Stabilization Shoulder Stabilization

    Shoulder instability is a chronic condition that causes frequent dislocation of the shoulder joint. A dislocation occurs when the end of the humerus (the ball portion) partially or completely dislocates from the glenoid (the socket portion) of the shoulder. A partial dislocation is referred to as a subluxation while a complete separation is referred to as a dislocation.

  • Subacromial Decompression Subacromial Decompression

    Subacromial decompression is a surgical procedure performed for the treatment of a condition called shoulder impingement. In shoulder impingement, the degree of space between the rotator cuff tendon and shoulder blade is decreased due to irritation and swelling of the bursa or due to development of bone spurs.

Others

  • Am I a Candidate for Shoulder Replacement? Am I a Candidate for Shoulder Replacement?

    Shoulder replacement is a surgical procedure where the damaged parts of your shoulder are removed and replaced with artificial parts known as prostheses.

  • Shoulder Fracture Care Shoulder Fracture Care

    A break in the bone that makes up the shoulder joint is called a shoulder fracture. The clavicle (collarbone) and end of the humerus (upper arm bone) closest to the shoulder are the bones that usually are fractured. The scapula, or shoulder blade, is not easily fractured because of its protective cover of surrounding muscles and chest tissue.

  • Triceps Repair Triceps Repair

    Triceps repair is a surgical procedure that involves the repair of a ruptured (torn) triceps tendon. A tendon is a tough band of fibrous tissue which connects muscle to bone and works together with muscles in moving your arms, fingers, legs, and toes. The triceps tendons connect the triceps muscles to the shoulder blade and elbow in your arm.

  • Am I a Candidate for Shoulder Surgery? Am I a Candidate for Shoulder Surgery?

    More people are considering shoulder surgery to manage shoulder problems thanks to advances in technology and equipment. Surgery is now minimally invasive and can be performed on an outpatient basis with faster recovery and fewer complications. But what are your other options and when is the right time to turn to surgery? Answer the following questions to see if shoulder surgery is ideal for you:

  • American Shoulder and Elbow Surgeons
  • American Academy of Orthopaedic Surgeons
  • American Board of Orthopaedic Surgery
  • Association of Clinical Elbow and Shoulder Surgeons
  • American Medical Association