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shoulder Instability

Normal Anatomy of the shoulder Joint

The shoulder is a most complex joint allowing us a great range of movement and flexibility. It is also susceptible to injury due to the delicate construction and balance of bones, ligaments, tendons and muscles making up the joint.

The shoulder consists of three bones: the collarbone (clavicle), the arm bone (humerus) and shoulder blade (scapular). Muscles and tendons help keep these bones in place providing strength and stability in the joint.

The shoulder is made up of two joints, the acromioclavicular joint (or AC joint) and the glenohumeral joint (or GH joint). The AC joint is located between the clavicle and the bony prominence on the upper edge of the scapular called the acromion. The GH joint is a ball and socket type joint which permits a great deal of movement in the shoulder.

The rotator cuff plays a significant role in the stability and flexibility of the shoulder. Consisting of four tendons the rotator cuff connects the muscles of the shoulder blade to the upper end of the humerus, holding this most active joint in place.

Bursae are small fluid filled sacs that cushion and lubricate the areas between bones, muscles and tendons. In the shoulder joint, a large bursa is found between the rotator cuff and the upper edge of the shoulder blade. They assist the smooth movement when you raise your arm.

It is this complex structure of ligaments, muscles and tendons which is often at the core of the most common shoulder problems. Some of these problems will be discussed in the next few pages of this booklet.

Many shoulder conditions can be treated, but often a cure, back to 100% normal, is not possible.

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Rotator Cuff Tear

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.

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shoulder Impingement

The term "shoulder impingement" is quite commonly used to describe a number of shoulder conditions that can often occur simultaneously. Bursitis, tendonitis and rotator cuff tears are symptoms of shoulder impingement and are the result of either mechanical compression and/or wear of the rotator cuff tendons.

Rotator cuff tendons usually glide smoothly between the acromion (upper edge of the shoulder blade) and the upper end of the humerus. When this action is compromised either due to degenerative changes, injury or overuse, the tendons become inflamed causing shoulder pain.

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shoulder Arthroscopy

A shoulder arthroscopy allows your surgeon to look inside your shoulder joint and perform a number of procedures using small instruments guided through tiny incisions made in the skin.

A small camera is inserted which relays pictures inside your joint back to a television in the operating theatre. Your surgeon is able to use specialised instruments to smooth rough surfaces, remove damaged tissue, cartilage or bone.

The small incisions allow surgery to be performed inside the joint with fewer traumas to the surrounding tissues. The small incisions are closed with sutures or small band aids and covered with a dressing and bandage. shoulder arthroscopy takes 1-2 hours and is most often a day procedure.

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Frozen shoulder

Frozen shoulder or adhesive capsulitis can occur as an isolated event or following a fracture, dislocation or other trauma where there may be reduced shoulder motion over a period of time.

Mobility in the shoulder is dependent on the correct alignment of the surrounding supporting ligaments. In adhesive capsulitis the ligaments become inflamed causing scar tissue to form. This in turn severely reduces (or freezes) the shoulders’ range of movement and causes significant joint pain. As the pain continues, the less the shoulder is moved thus contributing to the ‘frozen’ status of the joint.

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shoulder Joint Replacement

shoulder joint replacements are usually done to relieve pain and when all non-operative treatment to relieve pain has failed.

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shoulder Instability

shoulder instability can result from direct and forceful injury, which stretches the ligament capsule around the shoulder joint. This capsule is responsible for keeping the joint in alignment and functioning normally.

shoulder instability can also occur in people who naturally have relaxed or loose shoulder joints. These people are often referred to as ‘double jointed’.

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The shoulder is made up of two joints, the acromioclavicular (AC) joint where the collarbone (clavicle) and shoulder blade (scapula) meet and the glenohumeral (GH) joint where the upper end of the humerus and scapula form a ball and socket joint. Both can be affected by arthritis.

For more information about Osteoarthritis, click on below link.


Click on the topics below to find out more from the orthopaedic connection website of American Academy of Orthopaedic Surgeons.