Shoulder Injury and Surgery Patterns Among Astronauts Across Spaceflight Phases and Mission Operations: An Analysis...

Shoulder injuries are the most frequently reported musculoskeletal condition among astronauts, occurring across all spaceflight mission phases. With rising extravehicular activity (EVA) demands, a detailed understanding of injury patterns is critical. Prior studies have linked prolonged microgravity exposure to post-flight shoulder pathology but have not comprehensively characterized large-scale epidemiologic trends, phase-specific timing, or the influence of cumulative training exposures. Therefore, this study aimed to: (1) characterize overall prevalence, identify the top 20 diagnoses, and report the 5 most common surgical procedures; (2) compare injury distributions across spaceflight phases, including a post-flight sub-analysis stratified by <6 versus ≥6 months of microgravity exposure; and (3) determine associations between Neutral Buoyancy Laboratory (NBL) and EVA exposure durations and injury timing.

A retrospective review of the Lifetime Surveillance of Astronaut Health database identified musculoskeletal shoulder injuries and surgeries between 1981 and 2024 among NASA astronauts. Inclusion criteria required injuries to occur ≤5-years of a mission and be related to operational duties. Temporal mapping used days relative to mission timelines. Astronaut demographics, diagnoses, surgical procedures, and cumulative NBL and EVA exposure durations were collected. Chi-square tests assessed phase-specific injury distributions. Wilcoxon rank-sum tests compared post-flight injury timing in astronauts with <6 versus ≥6 months of microgravity exposure. Linear regression models evaluated associations between cumulative NBL and EVA hours and injury timing.

A total of 677 shoulder injuries and 25 surgical interventions were identified. The post-flight phase accounted for most injuries (64.8%), followed by pre-flight (33.6%) and in-flight (1.6%). The top diagnoses included tendinopathy (8.9%), osteoarthritis (7.8%), and rotator cuff injury (7.8%), with rotator cuff repair (32.0%) and arthroscopic debridement (28.0%) as the most common surgeries. Astronauts with ≥6 months of microgravity exposure experienced significantly earlier post-flight injury onset (P=0.040). Greater cumulative NBL exposure was associated with earlier pre-flight (R²=0.233; P=0.007) and post-flight injury timing (R²=0.119; P=0.009).

Over 43 years, astronauts sustained 677 shoulder injuries and 25 surgeries, with post-flight injuries significantly more frequent, and those exposed to ≥6 months of microgravity experiencing earlier onset. Increasing NBL exposure was also associated with accelerated post-flight injury timing, suggesting cumulative training stress as a key driver, an effect EVA exposure may mirror as lunar missions extend duration and frequency. These findings reinforce the need for targeted pre-flight conditioning, exposure-calibrated training thresholds, and post-flight surveillance models to preserve shoulder function and maintain mission readiness in next-generation spaceflight.