Is Muscle Weakness a Risk Factor of the Development of Rotator Cuff Tendinopathy – A Systematic Review

Abstract

BackgroundUnderlying muscle weakness may explain the inconsistency in the development of rotator cuff tendinopathy in population with similar activity levels. This systematic review aims to assess existing prospective studies to evaluate whether muscle weakness is a risk factor to the development of rotator cuff tendinopathy. MethodsA systematic search was performed using the PRISMA guidelines. Prospective studies measuring muscle strength or stiffness and the incidence of rotator cuff tendinopathy will be included. Quality assessment was performed with the Newcastle-Ottawa Quality Assessment Scale. ResultsThe search yielded 6 studies, with a total of 523 trained overhead athletes followed up for 1 season. External and internal rotation strength was described as protective factors for the development of rotator cuff tendinopathy, with an odds ratio of 0.940 (p < 0.05) and 0.946 (p < 0.01) respectively for each N/m increased in force generated. Limited range of motion of <106o for shoulder external rotation was also described as a risk factor with an odds ratio of 1.12 (p < 0.001).Imbalance between external and internal rotation strength was reported as a risk factor for shoulder injuries in 2 studies, with a relative risk of 2.57 (p < 0.05) reported in 1 of them. Supraspinatus weakness was also reported as a risk factor for shoulder injuries in 1 study, with no odds ratio or relative risk provided. Due to insufficient data, combination into a meta-analysis was not possible. ConclusionsLimited evidence support that weakness of the external rotators, weakness in the internal rotators, and limited range of motion in external rotation are risk factors to the development of rotator cuff tendinopathy. Very limited evidence support that imbalance in external rotator and internal rotator strength, and supraspinatus weakness are risk factors for rotator cuff tendinopathies. Future cohort studies may improve on existing evidence with investigations on more muscle groups, a longer follow-up time, clearly documented injury history, and a stringent diagnosis to rotator cuff tendinopathy.