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The Shoulder

The shoulder is the most flexible joint in the body. It allows a wide range of movements to the hands such as forward flexion, abduction, external rotation, internal rotation, adduction, and 360-degree circumduction. This however makes it the most insecure joint of the body as per the bone structure, but the support of ligaments, muscles and tendons gives it the required stability. Three bones, namely the bone of the upper arm (humerus), the shoulder blade (scapula), and the collar bone (clavicle) make up the shoulder joint.

The half-spherical head of the humerus forms a part of the shoulder joint.

The scapula is a flat triangular bone that can move freely and is suspended by muscles. It serves as the site for most of the muscles attachment, which plays an important role in stabilizing the joint. It has three bony protuberances called acromion, spine, and coracoid process. The acromion and coracoid processes serve as places for attachment of ligaments and tendons.

An irregular comma shaped shallow cavity in the scapula is called the glenoid cavity. The half-spherical head of the humerus fits into the glenoid cavity. A very small part of the head of the humerus makes contact with the glenoid cavity, thereby making it unstable. The extra stability is provided by the glenoid labrum, which is a ring of fibrous cartilage that surrounds the glenoid cavity and increases its depth and surface area to provide a better fit for the half-spherical head of the long arm bone.

The clavicle is an S-shaped collarbone. Most of the nerves pass from the neck to the arm, just below it and through the armpit. Nerves carry messages from the brain to the muscles, which move the bone, and also carry information about different sensations of touch, temperature and pain from the arm back to the brain.

Ligaments are thick strands of fibers that connect one bone to another. They connect the collarbone to the shoulder blade at the coracoid process (coracoclavicular ligaments) and at the acromion process (acromioclavicular ligament). Ligaments also connect the acromion process to the coracoid process (coracoacromial ligament). A group of ligaments form a capsule around the shoulder joint, and connect the head of the arm bone to the glenoid cavity of the shoulder blade (glenohumeral ligaments). Glenohumeral ligaments play a very important role in providing stability to the otherwise unstable shoulder joint and preventing dislocation.

Tendons are muscle extensions that join muscle to bone and allow the muscles to control the movement of the bone or joint. Two important groups of tendons in the shoulder joint are:

  • Bicep tendons are the two tendons that join the biceps muscles to the shoulder. They are called as long head and short head of biceps.
  • Rotator cuff is the group of four tendons that join the head of the humerus to the deeper muscles. It allows for more stability and mobility of the shoulder joint.

Summary
The shoulder joint is the most flexible, although a little complex, joint of the body. It allows a wide range of movements to the arms. To allow this free movement, the spherical head of the long bone of the arm fits loosely in the socket of the glenoid cavity of the shoulder bone. The stability and strength is provided by the supporting ligaments and tendons of the joint.

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Houston Shoulder Specialists

Advanced Orthopedics and sports medicine has numerous Board Certified/Eligible physicians who are thoroughly educated in the latest treatment techniques both surgical and conservative. They are well versed in advances in shoulder treatments including arthroscopic rotator cuff and Bankart repairs, shoulder stabilization procedures, total shoulder replacement and reverse shoulder replacement.

Drs Elbaz and Brooks now perform Platelet-Rich Plasma (PRP) injections for the treatment of rotator cuff tendinitis, and biciptal tendonitis. PRP stimulates a more rapid healing of tendon, ligament, muscle and bone.

Contact us today to Schedule an Appointment or call us at 281-955-2650 to learn more about our Shoulder Treatment options.

Our Locations
  • 1Professional Building II At North Cypress Medical Center
  • 2North Cypress Professional Building At Lakewood Crossing
  • 3North Cypress Professional Building At Towne Lake
  • 4Houston Professional Building

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