Individuals from a population based sample of 600 individuals aged 40 to 75 years that sustain a shoulder injury or a sudden onset of significant shoulder symptoms.

Bilateral shoulder MRI comparing the integrity of the rotator cuff tendons on pre-injury and post-injury MRI scans. Each of the four rotator cuff tendons (supraspinatus, infraspinatus, teres minor, subscapularis) will be assessed and graded for structural changes (normal, tendinopathy, partial thickness tear, full thickness tear). The dimensions of full thickness tears will be measured and recorded (size in millimeters).

Patient reported outcome measure. The Shoulder Pain and Disability Index (SPADI) was developed to measure current shoulder pain and disability in an outpatient setting. The SPADI contains 13 items that assess two domains; a 5-item subscale that measures pain and an 8-item subscale that measures disability. A SPADI total score ranging from 0 (best) to 100 (worst) is produced by averaging the two subscale scores.

The Constant-Murley Score was designed to assess the functional state of a shoulder and contains both physician- completed and patient-reported portions. The four domains include pain (15 possible points), activities of daily living (20 possible points), mobility (40 possible points), and strength (25 possible points). Scores range from 0 points (most disability) to 100 points (least disability).

The SSV score is defined as the subjective evaluation by the patient of shoulder function, expressed as a percentage of a normal shoulder. This score ranges from 0 to 100%.

The clinical examination will include orthopaedic shoulder tests used to assess rotator cuff integrity (internal rotation lag sign, lift off, press belly, hornblower sign, bear hug test, drop arm sign, external rotation lag sign).