Causes of Rotator Cuff Injuries (some are more like Risk Factors)
1.Age-related degeneration
2.Compromised microvascular supply
3.Outlet impingement
4.Instability
5.Other causes- e.g. falling, lifting and repetitive arm activities — especially those done overhead
Increase in frequency of partial-thickness and full-thickness tears with increasing age.
Increasingly after age 40, normal wear and tear on the rotator cuff can cause a breakdown of fibrous protein (collagen) in the cuff's tendons and muscles. This makes them more prone to degeneration and injury.
With age, one may also develop calcium deposits within the cuff or arthritic bone spurs that can pinch or irritate the rotator cuff.
2. Shoulder - tendinous area that receives very little blood supply.
The tendons of the rotator cuff muscles receive very little oxygen and nutrients from blood supply, and as a result are especially vulnerable to degeneration with aging. This is why shoulder problems in the elderly are common. This lack of blood supply is also the reason why a shoulder injury can take quite a lot of time to heal.
The bursal side of the supraspinatus tendon has a higher blood supply compared to the articular surface. This difference in blood supply causes the increase in articular surface tears compared with bursal tears.
3. Rotator cuff tendonitis is also known as impingement syndrome or shoulder bursitis
The shape of the acromion
3 types of acromions
Type I – Flat
Type II – Curved
Type III – Hooked
The rotator cuff contacts the coracoacromial arch undersurface in the normal shoulder.
The coracohumeral ligament is often resected in order to decompress the supraspinatus outlet, which can lead to increased superior translation of the humeral head, particularly in the young athlete.
Rotator cuff abrasions and fiber failure occur when repeated and excessive compression from humeral head migration is present.
This occurs secondary to underlying muscular imbalance and loss of rotator cuff depressor effects.
4. Most people with ligamentous laxity are functionally stable. In patients with inherent shoulder or generalized laxity, instability may develop with minimal or no injury.
Ligamentous laxity may be acquired by repetitive stretching of the joint, as observed in swimmers, gymnasts, and tennis players.
Dynamic stability may be lost if the shoulder becomes deconditioned. As a result, a vicious self-perpetuating cycle occurs :
Instability less use more muscle weakness More instability present
These patients frequently have relative rotator cuff muscle weakness, particularly the external rotators and scapular stabilizers.
Subtle instability patterns may contribute to the impingement development.
Increased anterior and superior translation of the humeral head, as observed in athletes with generalized laxity and multidirectional instability of the shoulder, may predispose to impingement along the coracoacromial arch, resulting in rotator cuff injury.
5. Other causes
Poor posture.
When slouching neck and shoulders forward, the space where the rotator cuff muscles reside can become smaller. This can allow a muscle or tendon to become pinched under the shoulder bones (including the collarbone), especially during overhead activities, such as throwing.
Falling.
Using arm to break a fall or falling on your arm can bruise or tear a rotator cuff tendon or muscle.
Lifting or pulling.
Lifting an object that's too heavy or doing so improperly — especially overhead — can strain or tear the tendons or muscles. Likewise, pulling something, such as a high-poundage archery bow, may cause an injury.
Repetitive stress.
Repetitive overhead movement of arms can stress the rotator cuff muscles and tendons, causing inflammation and eventually tearing. Common among athletes and people in the building trades, such as painters and carpenters
Tendinitis
Repetitive strain on the tendon
Most common cause of tendonitis. Tendonitis of the elbow, bicep, shoulder and hand is often developed by individuals that work on factory production lines and sports professionals.
Age related tendon changes
As the human body gets older the tendons get harder and lose their elasticity. This means that the joint is no longer as free to move and often flexibility is lost. As individuals get older they are much more prone to develop tendonitis. The cause of tendonitis from age is still not fully understood. It's suggested that as the body ages the change in blood vessels effects the tendons.
Putting the tendon under too much strain/ Overuse
This is the leading cause of tendonitis amongst strength athletes and bodybuilders. Tendonitis is developed when the individual puts the tendon under too much strain without properly warming up or under strain that the tendon simply cannot handle. This tendonitis cause can easily be avoided by using correct training techniques and exercise form
As a result of injury
It is not uncommon for tendonitis to develop as a result of another tendon or joint injury. For example, shoulder tendonitis is often developed after a rotator cuff injury and knee tendonitis can be developed after having knee surgery. In these cases tendonitis usually develops because the injury has not completely healed. This cause of tendonitis can easily be avoided by getting sufficient rest for the joint to recover from an injury completely.
As a result of another condition
In some cases diseases like rheumatoid arthritis or diabetes may cause tendonitis to occur. These cases are often rare and only occur when the individual puts the tendon under an unusual amount of pressure or strain.
Thermal injury to the tendon
A very uncommon cause of tendonitis and is often experienced by outdoor mountain climbers, rock climbers and hikers. In most cases the affected areas are the hands, wrists, ankles and feet.
Anatomical cause of tendonitis
Rare cause of tendonitis. If the tendon does not have a smooth surface area in which to work against it will often become inflamed and irritated quite easily. In these situations surgery is often required to realign the tendon.
References:
http://orthoinfo.aaos.org/topic.cfm?topic=A00064
http://emedicine.medscape.com/article/92814-overview
http://www.thestretchinghandbook.com/archives/rotator-cuff-injury.php#causes
http://www.creekayaker.com/shoulder/rotatorcuff-injury/Rotator%20Cuff%20Injury_files/image001.gifhttp://orthopedics.about.com/cs/sportsmedicine/a/tendonitis.htmhttp://www.itendonitis.com/shoulder-tendonitis.html
http://www.mlcmarlins.com.au/content/training/coaching_clinic/shoulders/images/image008.gif
http://www.creekayaker.com/shoulder/rotatorcuff-injury/Rotator%20Cuff%20Injury_files/image002.gif
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