Association Between Hormone Replacement Therapy and Incidence of Tendon Injuries and Surgical Repair in Perimenopausal Women: A Propensity Score–Matched National Cohort Study

Background: Tendinopathies are common in middle-aged women. While estrogen regulates tendon remodeling, the influence of systemic hormone replacement therapy (HRT) on the risk of tendon degeneration remains unclear. Hypothesis/Purpose: The purpose of this study was to investigate the association between systemic HRT use and tendon injuries/repair in perimenopausal women. It was hypothesized that systemic HRT would be associated with an increased incidence of tendon injuries and repair. Study Design: Cohort study; Level of evidence, 4. Methods: Using the TriNetX Research Network, we identified female patients aged ≥45 years diagnosed with major tendon abnormalities, including rotator cuff tears, bicipital tendinitis, lateral or medial epicondylitis, Achilles tendinopathy, patellar tendinitis, or quadriceps strain, from January 2004 to July 2025. HRT exposure was defined as systemic estrogen and/or progestin use within 1 year before a diagnosis. Patients with contraindications to HRT were excluded. After 1:1 propensity score matching, 2 groups of 63,836 patients each were generated. Primary outcomes included diagnosis rates of specific tendon conditions; secondary outcomes were lifetime rates of corresponding tendon repair procedures. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The independent t test and chi-square test were used for analysis. Results: HRT users had significantly higher rates of several tendon abnormalities compared to matched controls, including rotator cuff tears (39.2% vs 37.9%, respectively; P < .001), bicipital tendinitis (13.3% vs 11.0%, respectively; P < .001), lateral epicondylitis (27.8% vs 22.7%, respectively; P < .001), and medial epicondylitis (6.8% vs 5.3%, respectively; P < .001). Achilles tendinopathy had similar rates between the 2 groups (14.6% vs 14.5%, respectively; P = .387). Surgical repair was more common in the HRT group, including biceps tendon repair/tenodesis (3.9% vs 3.3%, respectively; OR, 1.16 95% CI, 1.10-1.23; P < .001), rotator cuff repair (6.6% vs 6.2%, respectively; OR, 1.06 95% CI, 1.01-1.11; P = .013), and Achilles tendon repair (0.7% vs 0.6%, respectively; OR, 1.23 95% CI, 1.06-1.41; P = .005). Conclusion: Our study showed that systemic HRT use in women aged ≥45 years was associated with an increased risk of tendon injuries and a greater likelihood of surgical repair, although the absolute risk differences were modest. These findings underscore the need for awareness of the possible musculoskeletal effects of hormone therapy and highlight an underexplored area in women's orthopaedic health.