The shoulder is the most flexible joint in the body enabling 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.
The shoulder is a ball and socket joint made up of three bones, namely the humerus, scapula, and clavicle.
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 glenohumeraljoint, which is the main joint of the shoulder.
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 sternoclavicularjoint 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.
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 shockabsorber 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 securefit for the half-spherical head of the humerus.
Ligaments are the thick strands of fibers that connect one bone to another. The ligaments of the shoulder joint include
- Coraco-clavicular ligaments: these ligaments connect the collarbone to the shoulder blade at the coracoid process
- Acromio-clavicular ligament: this connects the collarbone to the shoulder blade at the acromion process
- Coraco-acromial 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 water-tight sac around the joint. Glenohumeralligaments play a very important role in providing stability to the otherwise unstable shoulder joint by preventing dislocation.
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 awide 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 are strong tissues that join muscle to bone allowing the muscle to control the movement of the bone or joint. Two important group 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 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 passthrough 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 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 axillaryartery 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.
Rotator cuff is the group of tendons in the shoulder joint providing support and enabling wider range of motion. Major injury to these tendons may result in tear of these tendons and the condition is called as rotator cuff tear. It is one of themost common causes of shoulder pain in middle aged adults and older individuals.
Shoulder impingement is the condition of inflammation of the tendons of the shoulder joint. It is one of the most common causes of pain in the adult shoulder. The shoulder 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 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 term SLAP (superior –labrumanterior-posterior) lesion or SLAP tear refers to an injury of the superior labrum 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 thebody's natural response to injury.
Frozen shoulder, also called adhesive capsulitis is a condition characterized by pain and loss of motion in shoulder joint. It is more common in older adults aged between 40 and 60 years and is more common in women than men.
Shoulder instability is a chronic condition that causes frequent dislocations of the shoulder joint.
Acromioclavicular joint (AC joint) dislocation or shoulder separation is one of the most common injuries of the upper arm. It involves separation of the AC joint and injury to the ligaments that support the joint. The AC joint forms where theclavicle (collarbone) meets the shoulder blade (acromion).
The shoulder joint is a "ball and socket" joint that enables the smooth gliding and thereby the movements of arms. However, it is inherently unstable because of the shallow socket. A soft rim of cartilage, the labrum lines the socket and deepensit so that it accommodates the head of the upper arm bone better.
The thoracic outlet is a small passageway leading from the base of the neck to the armpit and arm. This small area contains many blood vessels, nerves and muscle. When this passageway becomes compressed the condition is termed as thoracic outletsyndrome. This rare condition is characterized by burning pain in the neck and shoulder, numbness and tingling of the fingers, and a weak hand grip.
Playing more overhead sports activities and repeated use of shoulder at workplace may lead to sliding of the upper arm bone, the ball portion, from the glenoid–the socket portion of the shoulder.
The shoulder joint is a ball and socket joint. A 'ball' at the top of the upper arm bone (the humerus) fits 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.
Burners and stingers are common neck or shoulder injuries characterized by intense burning or stinging pain which can radiate from the neck to the hand. They are caused by sudden movement or a direct blow to the neck resulting in an injury tothe brachial plexus. This injury is commonly seen in contact sports such as football, ice hockey, wrestling, and rugby.
Shoulder injuries most commonly occur 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.
Clavicle fracture, also called broken collarbone is a very common sports injury seen in people who are involved in contact sports such as football and martial arts as well as impact sports such as motor racing. A direct blow over the shoulderthat may occur during a fall on an outstretched arm or a motor vehicle accident may cause the clavicle bone to break. Broken clavicle may cause difficulty in lifting your arm because of pain, swelling and bruising over the bone.
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.
The shoulder is a highly movable body joint that allows various movements of the arm. It is a ball and socket joint, where the head of the humerus (upper arm bone) articulates with the socket of the scapula (shoulder blade) called the glenoid. The two articulating surfaces of the bones are covered with cartilage, which prevents friction between the moving bones. The cartilage is lubricated by synovial fluid.
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 orsocket) is left intact. This surgical procedure is indicated in severe, persistent conditions of shoulder osteoarthritis in which the only the humeral head or ball of the joint is damaged.
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. In an arthritic shoulder
Reverse total shoulder replacement, is an advanced surgical technique specifically designed for rotator cuff tear arthropathy, a condition where the patient suffers from both shoulder arthritis and a rotator cuff tear.
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 cartilagesurrounding the glenoid which helps in stabilizing the shoulder joint.
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 toproject images to a computer screen for your surgeon to view the surgical site.