Background Tendinopathies of the patellar and Achilles tendons are common injuries among athletes and the general population. These injuries are costly, time-intensive to treat, and significantly limit activity. Predicting and eventually preventing these injuries is invaluable.

Objective Evaluate the relationship between sonographic tendon abnormalities and development of future injury in community marathon runners.

Design Prospective longitudinal cohort study. A blinded reviewer rated pre-race ultrasound images for tendon abnormalities, including thickening, hypoechogenicity, intratendinous delamination, or calcifications.

Setting 2019 Salt Lake City Marathon

Participants Marathon or half-marathon runners with no knee or ankle symptoms. 166 were screened; 138 completed the study (36.2 ± 12.0 years of age, male: n=68).

Assessment of Risk Factors Ultrasound evaluation of bilateral Achilles and patellar tendons immediately prior to the race and longitudinal surveys of subsequent injury development immediately following the race, and 1 and 3 months post-race.

Main Outcome Measurements Patellar or Achilles injury development. Statistical analyses included calculating relative risk (RR) with a 95% confidence interval (CI) and hazard ratio (HR) with a 95% CI from the Cox proportional hazards (PH) model.

Results Sonographic abnormalities were found among 12.3% (left Achilles) and 26.8% (right patellar) of runners. Runners with sonographic abnormalities were 2 times (RR = 2.20, 95% CI = 1.15, 4.22, p = .040) more likely to develop pain in the Achilles tendon within three months compared to those with normal ultrasounds. The Cox PH model indicated that sonographic abnormalities were associated with 2 times (HR = 2.35, 95% CI = 1.10, 4.99, p = .027) higher risk of developing post-race pain in the Achilles tendon after adjusting for runners’ demographics and training regimens. No significant findings were observed between sonographic abnormality and post-race pain in the patellar tendon for the current observation period.

Conclusions Pre-race sonographic Achilles tendon abnormalities are associated with development of Achilles tendon pain within 3 months. Subsequent injury development, including at 6, 9, and 12-months post-race is pending.