How is Supraspinatus Tendinopathy Caused?
Supraspinatus tendinopathy occurs commonly from overloading the shoulder with repetitive or heavy weighted activities, especially overhead activities. A change in sport or gym program, or starting a new sport or gym program may also make a person more susceptible to sustaining a supraspinatus injury (Axis Physiotherapy, n.d.).
Supraspinatus tendinopathies are injuries that result from many gradual tiny tears (microtears) in the tendon of the supraspinatus muscle over time (Wikipedia, 2009). The microtear usually occurs at the point of insertion (attachment of tendon at head of humerus). Microtears can occur due to intrinsic (within the muscle structure) and extrinsic (damage due to surrounding structures) factors.
Intrinsic Factors
· Mechanical properties
· Tendon load past physiological threshold
· Intrinsic degeneration
· Age: influences the mechanical properties of the tendon. Calcification of tendons is common in the elderly and alters the biomechanics of the shoulder leading to a greater susceptibility to microtears (Mehta, Gimbel, & Soslowsky, 2003). The elderly also have a decreased healing capacity compared to younger people and are therefore at greater risk of re-injury (Mehta, Gimbel, & Soslowsky, 2003).
· Non-uniform stress: results in excessive load being concentrated to specific areas of the tendon leading to localized fibre damage (Sharma &Marffulli, 2005).
The damage that occurs to the supraspinatus tendon must be actively repaired (i.e. through
exercises or therapy) or the tendon will continue to weaken and rupture of the tendon may
eventually occur (Sharma &Marffulli, 2005).
Extrinsic Factors
· Impingement or compression of muscle or tendon by bony or ligamentous structures surrounding the tendon, specifically the coracoacromial arch, located at the top of the shoulder (Mehta, Gimbel, & Soslowsky, 2003).
· Internal impingement (within shoulder joint).
· External impingement (subacromial space): thought to be primary cause (Mehta, Gimbel, & Soslowsky, 2003).
· Glenohumeral (shoulder) joint instability increases a persons vulnerability to supraspinatus injury, specifically damage to the inferior glenohumeral ligament. The inferior glenohumeral ligament maintains the anterior (front) stability of the shoulder; therefore damage to this ligament alters the mechanics of the shoulder and may result in a tendinopathy (Mehta, Gimbel, & Soslowsky, 2003).
