Early trials of intra-articular corticosteroids showed equal systemic absorption of methylprednisolone in patients with rheumatic and osteoarthritic hands 42 and knees. 43 This suggests that steroid pharmacokinetics, rather than disease-related factors, should guide steroid selection. A recent review by the National Health Service of the United Kingdom 44 recommends triamcino-lone and methylprednisolone as preferred agents for injection of large joints (., knee). For smaller joints (., finger), either hydrocortisone or methylprednisolone (Hydeltrasol, brand no longer available in the United States) is recommended. Tables 5 and 6 45 compare commonly available steroid preparations.
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 humerus, glenoid, scapula, acromion, clavicle and surrounding soft tissues make up the shoulder. There are three significant articulations: the sternoclavicular joint, the acromioclavicular joint and the glenohumeral joint. The glenohumeral joint is the most commonly dislocated major joint in the body.
Ligaments and surrounding musculature, including the rotator cuff muscles, contribute to shoulder joint stability. The rotator cuff is composed of the four muscles: supraspinatus, infraspinatus, teres minor and subscapularis that interlock to function as one unit. These muscles help with internal and external rotation of the shoulder and importantly depress the humeral head against the glenoid as the arm is elevated. The tendons join together to form one tendon, the rotator cuff tendon. This passes through the subacromial space. The subacromial bursa, which has a large number of pain sensors, fills the space between the acromion and the rotator cuff tendon. [ 1 ]