The shoulder is one of the most complex joints in the human body. In view of this complexity making the correct diagnosis in shoulder disorders normally requires a thorough history and examination by an experienced professional.The main part of the shoulder is a ball and socket joint (glenohumeral joint). However, the shoulder girdle comprises a complex system of muscles, tendons, ligaments, bones and joints, which all need to interact together in a co-ordinated manner to allow the shoulder to function normally.
Unlike the hip joint where the socket is deep and the joint is naturally stable, the socket of the shoulder joint is shallow which allows the shoulder it's exceptionally large range of motion. This also makes the joint inherently unstable. The socket (glenoid) of the joint is part of the shoulder blade (scapula) which glides and rotates over the ribs at the back of the chest, allowing the shoulder complex an even greater range of movement. The collar bone or clavicle at the front of the shoulder acts like a strut, supporting the scapula. It attaches to the shoulder blade by a joint called the acromioclavicular joint.
There are a large number of muscles, tendons and ligaments around the shoulder joint all acting together in a complex fashion giving movement, strength and stability. Any one or combination of these soft tissues, bones or joints in and around the shoulder can suffer from disorders such as traumatic injuries or degeneration, producing a wide range of symptoms. Of particular importance are 4 msucles which are wrapped like a sleeve aroung the arm known as the 'rotator cuff'. Shoulder symptoms include pain, stiffness, instability, mechanical symptoms and weakness
Pain in the shoulder can arise from a number of conditions including rotator cuff disorders (tendinopathy / calcific tendinitis / impingement / subacromial bursitis / tendon tears), glenohumeral joint disorders (capsulitis ' frozen shoulder' / arthritis) and acromioclavicular joint disorders. Pain in or around the shoulder is a very common problem. The site and nature of the pain are important indicators of what the potential cause might be.
Pain at the front of the shoulder can be due to:- Biceps tendonitis or acromioclavicular joint arthritis.
Pain over the top of the shoulder may be caused by:- Subacromial impingement, rotator cuff tears, supraspinatus tendonitis or tendinosis, calcific tendonitis or acromioclavicular joint arthritis.
Pain when lifting the arm up sideways is most often due to:- Subacromial impingement, acromioclavicular joint arthritis, supraspinatus tendonitis or rotator cuff tears.
Most problems affecting the shoulder joint tend to cause at least some degree of stiffness and restricted movement. When a shoulder has globally reduced movements in all directions then the most common causes are either arthritis or a frozen shoulder. It is important to distinguish between the two as treatment options vary.
The very nature of the shoulder joint is that it is very mobile. This mobilty carries with it the potential risk of instability. When a joint comes out completely, ie the ball comes completely out of the socket, it is described as 'dislocated'. When the joint only comes part way out it is referred to as 'subluxing'.
The shoulder can be dislocated through injuries such as falls. Alternatively, some people have naturally loose shoulder joints that they can voluntarily dislocate and pop back in at will. If a shoulder joint is dislocated through trauma, then the more times it recurrently dislocates, the more likely it is to dislocate once again at some stage in the future, often with increasingly minor causes. Recurrent traumatic dislocation of a shoulder joint is a serious problem that is best treated by surgical stabilisation.
One other form of dislocation/subluxation that can occur in/around the shoulder is dislocation of the acromioclavicular joint (the joint between the clavicle (collar bone) and the front of the shoulder blade. This is a very common injury in some sports such as rugby. It causes pain and swelling at the outer end of the collar bone and may or may not need surgical treatment, depending on how severe the dislocation is, how bad the symptoms are and what employment/sports the patient participates in.
Painless clicking in joints is a common phenomenon and is usually of little or no relevance. However, when a joint clicks and the clicking is painful, then this is more serious as it implies that there may be something catching within the joint, such as a loose piece of cartilage, a torn piece of cartilage or some unstable structure, such as a tendon. Painful clicking in a joint is usually worth investigating further.
Any joint that is painful will most probably feel weak. However, weakness associated with specific movements in certain directions can indicate damage to specific structure, such as the rotator cuff tendons. For example, weakness in lifting the arm up sideways in particular may be due to a rotator cuff tear.