Rotator cuff tear has a multifactorial etiology. Age [1–3], altered biology [4, 5], tendon hypovascularity [6–9], smoking habit [10, 11], and tendon overload-overuse [12, 13] are generally believed to be intrinsic factors. They are responsible for a series of cellular changes mainly represented by increased matrix metalloproteinases and reduced tissue inhibitors of metalloproteinases [14, 15], nitric oxide synthetases [16], and chondroid metaplasia [17]. All of these changes disturb the turnover rate and proliferation of collagen, leading tendon to degeneration and apoptosis [18–20].

Distinct anatomic variants of the scapula (subacromial and subcoracoid impingement), acromioclavicular joint arthropathy, and pathology of the thoracic spine (thoracic hyperkyphosis) are usually listed among the extrinsic factors causing cuff tear. According to the extrinsic theory, anatomic structures are responsible, in a dynamic fashion, for degenerative changes observed in rotator cuff tendinopathy.

References

1. Milgrom C, Schaffler M, Gilbert S, van Holsbeeck M (1995) Rotator-cuff changes in asymptomatic adults. The effect of age, hand dominance and gender. J Bone Joint Surg Br 77:296–298

2. Tempelhof S, Rupp S, Seil R (1999) Age-related prevalence of rotator cuff tears in asymptomatic shoulders. J Shoulder Elbow Surg 8:296–299

3. Gumina S, Carbone S, Campagna V, Candela V, Sacchetti FM, Giannicola G (2013) The impact of aging on rotator cuff tear size. Musculoskelet Surg 97(Suppl 1):69–72. doi:10.​1007/​s12306-013-0263-2

4. Kumagai J, Sarkar K, Uhthoff HK (1994) The collagen types in the attachment zone of rotator cuff tendons in the elderly: an immunohistochemical study. J Rheumatol 21:2096–2100

5. Riley GP, Harral RL, Constant CR, Chard MD, Cawston TE, Hazleman BL (1994) Glycosaminoglycans of human rotator cuff tendons: changes with age and in chronic rotator cuff tendinitis. Ann Rheum Dis 53:367–376