Further subclasses include the acromiohumeral distance, acromial shape, fatty infiltration or degeneration of muscles, muscle atrophy, tendon retraction, vascular proliferation, chondroid metaplasia, and calcification. Again, in surgical planning, age-related degeneration of thinning and disorientation of the collagen fibers, myxoid degeneration, and hyaline degeneration are considered.Diagnostic modalities, dependent on circumstances, include X-ray, MRI, MR arthrography, double-contrast arthrography, and ultrasound. Although MR arthrography is currently considered the gold standard, ultrasound may be most cost-effective. Usually, a tear will be undetected by X-ray, although bone spurs, which can impinge upon the rotator cuff tendons, may be visible. Such spurs suggest chronic severe rotator cuff disease. Double-contrast arthrography involves injecting contrast dye into the shoulder joint to detect leakage out of the injured rotator cuff  and its value is influenced by the experience of the operator. The most common diagnostic tool is magnetic resonance imaging (MRI), which can sometimes indicate the size of the tear, as well as its location within the tendon. Furthermore, MRI enables the detection or exclusion of complete rotator cuff tears with reasonable accuracy and is also suitable to diagnose other pathologies of the shoulder joint.The logical use of diagnostic tests is an important component of effective clinical practice.Clinical judgement, rather than over reliance on MRI or any other modality, is strongly advised in determining the cause of shoulder pain, or planning its treatment, since rotator cuff tears are also found in some without pain or symptoms.
Though the supraspinatus is the most commonly injured tendon in the rotator cuff, the other three can also be injured at the same time. Acute tears
The amount of stress needed to acutely tear a rotator cuff tendon will depend on the underlying condition of the tendon. If healthy, the stress needed will be high, such as with a fall on the outstretched arm. This stress may occur coincidentally with other injuries such as a dislocation of the shoulder or separation of the acromioclavicular joint. In the case of a tendon with pre-existing degeneration, the force may be more modest, such as with a sudden lift, particularly with the arm above the horizontal position. The type of loading involved with injury is usually eccentric, such as when two people are carrying a load and one lets go, forcing the other to maintain force while the muscle elongates. Chronic tears
Chronic tears are indicative of extended use in conjunction with other factors such as poor biomechanics or muscular imbalance. Ultimately, most are the result of wear that occurs slowly over time as a natural part of aging. They are more common in the dominant arm, but a tear in one shoulder signals an increased risk of a tear in the opposing shoulder.Several factors contribute to degenerative, or chronic, rotator cuff tears of which repetitive stress is the most significant. This stress consists of repeating the same shoulder motions frequently, such as overhead throwing, rowing, and weightlifting.