Research Shows Pitchers Have Thicker UCL Ligaments in the Elbow, Heightening Injury Risks

Every baseball season, players at all levels, from youth leagues to professional ranks, face the risk of elbow injuries involving the ulnar collateral ligament (UCL). A recent study led by researchers from the University of Kansas employed advanced ultrasound technology to measure UCL thickness among collegiate baseball players. The findings revealed that pitchers tend to have thicker UCLs compared to non-pitchers, likely due to the higher volume and intensity of throws they execute.

Participants in the study included 22 NCAA Division I players, with ultrasound scans and elbow torque measurements taken during preseason training. Players wore sleeves embedded with accelerometers to quantify elbow stress during their pitching routines. Results confirmed that pitchers' UCLs were significantly thicker in their throwing arms versus their non-throwing arms, emphasizing the impact of repetitive, high-force throwing motions.

Interestingly, the research found no correlation between arm slot—the angle at which a player throws—and UCL thickness, challenging conventional wisdom that certain arm angles pose higher injury risks. Instead, factors such as increased elbow torque, effort level during throws, and volume of throws were linked to greater UCL thickness, which may indicate a higher risk for injury.

The study's insights are valuable for coaches, trainers, and athletes aiming to develop better mechanics and conditioning programs to prevent UCL injuries. Understanding how high-stress throwing behaviors influence ligament health can inform strategies to minimize injury risks, including managing throw volume and effort levels.

UCL injuries are commonly treated with "Tommy John" surgery, especially in pitchers, but they are also experienced by positional players. Previous research indicated a relationship between UCL size and injury risk, and ultrasound technology now offers the potential to detect ligament changes before injuries occur.

Furthermore, the study dispelled myths about the influence of arm position on ligament thickness, showing that factors like height, weight, or even-handedness do not predict optimal arm slots for pitching. Instead, emphasis should be placed on managing throw effort and volume.

Authoritative voices like Quincy Johnson from KU highlight the importance of ongoing research into injury prevention practices and biomechanics, advocating for data-driven approaches to safer sports participation. This research may help reduce the financial, physical, and career impacts associated with UCL injuries, ultimately promoting healthier athletic development.

For more detailed results, see the full study: Calvin Smith et al, "Influence of Throwing Kinematics on Ulnar Collateral Ligament Thickness in Collegiate Baseball Players," Orthopaedic Journal of Sports Medicine (2025).