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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.

Proximal Biceps Tenodesis

Proximal biceps tenodesis is the surgical reattachment of a torn proximal biceps tendon, which connects the upper part of your biceps muscle to the shoulder.

 

Open Shoulder Stabilization

Open shoulder stabilization is a surgical procedure performed to treat a condition called shoulder instability. Shoulder instability is a chronic condition that causes the 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.

 

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.

 

Shoulder Reconstruction Surgery

Shoulder reconstruction surgery is an operative procedure in which stretched or torn soft-tissue structures that surround the shoulder joint such as the capsule, ligaments, and cartilage, are repaired to secure the shoulder joint in place. The procedure is mainly employed for the treatment of individuals with shoulder instability, to prevent recurrent joint dislocations, and to restore normal shoulder range of motion and function.

 

AC Joint Stabilization

Acromioclavicular (AC) joint stabilization is a surgical procedure employed to treat severe cases of AC joint dislocation. AC joint dislocation is the separation of the collar bone or clavicle from the acromion (the top portion of the shoulder blade or scapula at the outer edge of the shoulder) due to severe trauma.

 

Non-surgical Shoulder Treatments

Rest plays an important role in restoring shoulder health and shouldn’t be taken lightly. Usually, a sling is worn to keep the arm immobile and stable. You should try to avoid using the injured arm as straining the injured shoulder may lead to future complications. Physical rest can also help keep inflammation under control.

 

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

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.

 

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

A SLAP repair is an arthroscopic shoulder procedure to treat a specific type of injury to the labrum called a SLAP tear. A superior labrum anterior and posterior tear or SLAP tear is an injury to the labrum. This injury may also involve the biceps tendon, which is attached to the top part of the labrum. The injury occurs from repeated use of the shoulder while throwing or a fall onto the shoulder.

 

Arthroscopic Bankart Repair

The labrum can sometimes tear during a shoulder injury. A specific type of labral tear that occurs when the shoulder dislocates is called a Bankart tear. This is a tear to a part of the labrum called the inferior glenohumeral ligament and is common in the young who sustain a dislocation of the shoulder. A Bankart tear makes the shoulder prone to repeat dislocation in patients under 30 years of age.

 

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 Labrum Reconstruction

The shoulder joint is a ball and socket joint. A ball at the top of the upper arm bone (the humerus) fits neatly into a socket, called the glenoid, which is part of the shoulder blade (scapula). The labrum is a ring of fibrous cartilage surrounding the glenoid, which helps in stabilizing the shoulder joint.

 

Shoulder Stabilization

Shoulder stabilization surgery is performed to improve stability and function to the shoulder joint and prevent recurrent dislocations. It can be performed arthroscopically, depending on your particular condition, with much smaller incisions. Arthroscopic stabilization is a surgical procedure to treat chronic instability of the shoulder joint.

 

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 surgeon to clearly view. Arthroscopy is used to treat disease conditions and injuries involving the bones, cartilage, tendons, ligaments, and muscles of the shoulder joint.

 

Partial Shoulder Replacement (Shoulder Hemiarthroplasty)

Partial shoulder replacement, also called shoulder hemiarthroplasty, is a surgical procedure during which the upper bone in the arm (humerus) is replaced with a prosthetic metal implant, whereas the other half of the shoulder joint (glenoid or socket) is left intact.

 

Open Glenoid Bone Grafting

The glenoid, also called the glenoid cavity or glenoid fossa, is a shallow depression in the shoulder blade (scapula) that connects the upper arm bone (humerus) with the collar bone (clavicle). Open glenoid bone grafting is a surgical procedure in which a damaged area of the glenoid (with bone loss or missing bone) is replaced with a bone graft (healthy bone tissue) obtained from your body, such as the iliac crest, or with an allograft, a synthetic, artificial, or natural bone substitute.

 

AC Joint Repair

AC joint repair is a surgical procedure performed to repair damaged or torn ligaments and tendons of the acromioclavicular (AC) joint. Depending on the severity of the injury, the surgery can be done through tiny keyhole incisions arthroscopically, or as open surgery through a relatively larger skin incision.

 

ORIF Proximal Humerus Fracture

A proximal humerus fracture is a break in the upper arm bone near the shoulder joint. This type of fracture can severely affect the shoulder joint and immediate medical attention is required in order to preserve shoulder function. A fracture to the humerus bone is a possible consequence of a traumatic event, such as a fall or forceful collision.

 

Shoulder Capsular Repair

Shoulder capsular repair is a surgical procedure to treat shoulder instability that does not improve with more conservative or non-surgical methods. The shoulder joint, also referred to as the glenohumeral joint, is a ball and socket joint, formed by the bone of the upper arm (humerus), which articulates with the shoulder blade (scapula) in a cavity called the glenoid fossa.

 

Revision Rotator Cuff Surgery

Revision rotator cuff surgery is a procedure done to repair a re-tear in the rotator cuff after a failed initial rotator cuff surgery. The revision surgery is generally more complex, as it attempts to repair a rotator cuff that has been torn multiple times.

 

Platelet-Rich Plasma (PRP) for the Shoulder

Platelet-Rich Plasma (PRP) therapy is a regenerative treatment option that involves injecting a concentrated solution of platelets obtained from the patient's own blood into the shoulder joint. This therapy can be used to promote healing, reduce inflammation, and relieve pain associated with shoulder injuries and conditions.

 

Shoulder Anterior Labral Repair

A shoulder anterior labral repair is a surgical procedure performed to address damage or injury to the anterior (front) labrum of the shoulder joint. The labrum is a ring of cartilage that surrounds the shoulder socket (glenoid) and helps stabilize the joint. Injuries to the labrum can occur due to trauma, repetitive overhead motion, dislocation, or other shoulder-related issues.

 

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.

 

Rotator Cuff Tear

The 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 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. In addition to pain, shoulder injuries also cause stiffness, restricted movements, difficulty in performing routine activities and popping sensation.

 

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. Anterior shoulder instability accounts for 95 percent of all acute traumatic shoulder dislocations.

 

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.

 

SLAP Tears

The term SLAP (superior–labrum anterior-posterior) lesion or SLAP tear refers to an injury of the superior labrum of the shoulder. The most common causes include falling on an outstretched arm, repetitive overhead actions such as throwing and lifting a heavy object. Overhead and contact sports may put you at a greater risk of developing SLAP tears.

 

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.

 

Shoulder Instability

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

 

Shoulder Labral Tear

The shoulder joint is a ball and socket joint. A ball at the top of the upper arm bone (humerus) fits neatly into a socket, called the glenoid, which is part of the shoulder blade (scapula). The glenoid is surrounded by a ring of fibrous cartilage called the labrum for stabilization of the shoulder joint.

 

Shoulder Ligament Injuries

Shoulder ligament injuries are injuries to the tough elastic tissues present around the shoulder that connect bones to each other and stabilize the joint. The ligaments present in the shoulder are connected to the ends of the scapula, humerus, and clavicle bones which form the shoulder complex. The extensive stretching or tearing of these ligaments from acute or chronic injuries can lead to instability in the shoulder joint.

 

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.

 

Shoulder Fracture

A break in a bone that makes up the shoulder joint is called a shoulder fracture. The clavicle and end of the humerus closest to the shoulder are the bones that usually get fractured. The scapula, on the other hand, is not easily fractured because of its protective cover by the surrounding muscles and chest tissue.

 

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.

 

Fracture of the Shoulder Blade (Scapula)

The scapula (shoulder blade) is a flat, triangular bone providing attachment to the muscles of the back, neck, chest, and arm. The scapula has a body, neck, and spine portion.

 

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

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.

 

Proximal Biceps Tendonitis

Proximal biceps tendonitis 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.

 

Shoulder Bursitis

Shoulder bursitis, also known as subacromial bursitis, is a condition characterized by pain and inflammation in the bursa of the shoulder. The bursa is a fluid-filled sac present between the bone and soft tissue that acts as a cushion and helps to reduce friction during movement.

 

AC Joint Separation

AC joint separation, also known as shoulder separation, is a condition characterized by damage to the ligaments that connect the acromion to the collar bone. As a result, the bones do not line up properly, causing joint pain and instability.

 

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.

 

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.

 

Acromioclavicular Joint Sprains

The collarbone and the shoulder blade are connected by the acromioclavicular joint. This is supported by a strong band of ligaments called the acromioclavicular and coracoclavicular ligaments. These ligaments are tightly wound around the bones, providing strength and support to the joint. An injury or tear of these ligaments can result in an acromioclavicular joint sprain.

 

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.

 

Biceps Tendon Rupture

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.

 

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.

 

Rotator Cuff Bursitis

The rotator cuff is a set of muscles and tendons which hold the various bones of the shoulder joint together, providing strength and support. Inflammation of the bursa, a fluid-filled sac between the rotator cuff tendons and a bony process at the top of the shoulder called the acromion, is known as shoulder bursitis or rotator cuff bursitis.

 

Rotator Cuff Pain

The rotator cuff consists of a group of tendons and muscles that surround and stabilize the shoulder joint. These tendons allow a wide range of movement of the shoulder joint across multiple planes. Irritation or injury to these tendons can result in rotator cuff pain.

 

Acromioclavicular (AC) Joint Injuries

The acromioclavicular (AC) joint in the shoulder is very important for shoulder strength, motion, and maintaining shoulder position. The joint is stabilized by various ligaments and a capsule, which can cause pain and affect normal joint function if damaged.

 

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  • American Board of Orthopaedic Surgery
  • American Shoulder and Elbow Surgeons
  • American Academy of Orthopaedic Surgeons
  • Michigan State University