Pathophysiology and complications of tendonitis and tendinosis

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Rotator cuff injury
The rotator cuff is the network of four muscles and several tendons that form a covering around the top of the upper arm bone (humerus). These muscles form a cover around the head of the humerus. The rotator cuff holds the humerus in place in the shoulder joint and enables the arm to rotate.
Rotator cuff tear is a common cause of pain and disability among adults. Most tears occur in the supraspinatus muscle, but other parts of the cuff may be involved.
The terms tendinitis, tendinosis, and tendinopathy all refer to tendon injuries. These terms are commonly confused and misused. The term paratenonitis refers to an injury of the outer layer of tendon; this newer term replaces the older terms peritendinitis, tenosynovitis, and tenovaginitis.
tendinitis The suffix "itis" means inflammation. The term tendinitis should be reserved for tendon injuries that involve larger-scale acute injuries accompanied by inflammation. (Tendinitis is often misspelled as tendonitis, but the preferred spelling used in most of the medical literature is tendinitis.)
tendinosis The suffix "osis" implies a pathology of chronic degeneration without inflammation. Doctors prefer the term tendinosis for the kind of chronic tendon injuries that most of us have. The main problem for someone with tendinosis is failed healing, not inflammation; tendinosis is an accumulation over time of microscopic injuries that don't heal properly. Although inflammation can be involved in the initial stages of the injury, it is the inability of the tendon to heal that perpetuates the pain and disability. Most of the pain associated with tendinosis probably comes not from inflammation but from other irritating biochemical substances associated with the injury
tendinopathy The suffix "opathy" implies no specific type of pathology, so the term tendinopathy is more general than either tendinitis (inflammation) or tendinosis (failed healing). The term tendinopathy just means tendon injury, without specifying the type of injury.
degeneration of the tendon itself, tendinosis, and degeneration/inflammation of the tendon sheath, paratenonitis).

Tendinopathy
Pathophysiology
· Tendinits
o inflammation or irritation of a tendon — any one of the thick fibrous cords that attach muscles to bones. The condition, which causes pain and tenderness just outside a joint, can occur in any of your body's tendons. Tendinitis is common around your shoulders, elbows, wrists and heels.
· Tendinosis
o Internal tendon degeneration due to imbalance in tendon repair and tendon breakdown (increase in breakdown or decrease in healing response)
o Tendinosis is an accumulation over time of small-scale injuries that don't heal properly; it is a chronic injury of failed healing. Although you can't see the tendinosis injury on the outside of your body, researchers have seen what the injury looks like on the cellular scale by viewing slides of tendons under the microscope.
Complications
· Tendonitis
o Leads to rupture of a tendon
o Cause permanent damage to the tissue that makes up tendons
o May progress to tendinosis or other tendinopathy
o This may change the structure of the tendon to weaker more fibrous tissue
· Tendinosis
o lead to reduced tensile strength
o increasing the chance of tendon rupture
o

http://www.mayoclinic.com/health/rotator-cuff-injury/DS00192
http://orthoinfo.aaos.org/topic.cfm?topic=A00064
http://www.sosmed.org/pdffiles/patientguides/PatGuideCuffTendinosis.pdf