Pitch-Tracking Risk Factors and Warning Signs for Shoulder Capsulolabral Injuries in Major League Baseball Pitchers

Shoulder capsulolabral injuries are a major source of disability in Major League Baseball (MLB) pitchers. The introduction of Statcast pitch tracking now enables population-level analysis of shoulder injury mechanisms.

The purpose of this study was to identify preinjury kinematic risk factors for arthroscopic capsulolabral repair. It was hypothesized that pitchers who sustain capsulolabral injuries show preinjury kinematic deviations detectable on Statcast data.

Case-control study; Level of evidence, 3.

MLB pitchers undergoing primary capsulolabral repair between 2017 and 2024 (n = 27) were matched 1:2 to uninjured controls (n = 54) by age, role, handedness, season, and pitch count. Statcast pitch-level data were analyzed across 2 consecutive seasons preceding surgery, yielding 161,979 pitches. Six kinematic variables (release speed, spin rate, arm angle, extension, and horizontal and vertical release position) were extracted across 7 pitch types. To identify potential risk factors and preinjury warning signs, 3 complementary analyses were performed. First, a baseline analysis compared mean kinematic profiles and within-outing variability during the preinjury season (season 1) to characterize potential inherent risk profiles. Second, a longitudinal analysis evaluated change scores across 3 intervals including within season 1, across the winter offseason, and within the injury season, by comparing the first 3 versus last 3 qualifying outings of each period to assess potential progressive trends preceding surgery. Third, to identify acute warning signs, a separate analysis modeled linear trends across the final 5 outings immediately preceding injured list placement. Analyses used linear mixed-effects models with clustered standard errors.

At baseline (season 1), cases demonstrated significantly higher mean velocity and spin, and lower variability in arm angle and release speed, compared with controls across pitch types. On 4-seam fastballs and sinkers, this corresponded to approximately +1.46 mph and +1.57 mph higher velocity (P = .009 and P = .006, respectively). Standardized effects showed higher spin rate (β = +0.32 SD; P = .02) and lower variability in arm angle (β = -0.58 SD; P = .005) and release speed (β = -0.37 SD; P = .007). During the injury season (season 2), cases showed a significantly greater decline in velocity on fastballs (-0.68 mph; P = .009) and breaking balls (-1.07 mph; P = .003). In the final 5 outings before surgery, cases demonstrated a progressive, linear loss on fastball velocity (-0.20 mph/outing) and breaking ball velocity (-0.30 mph/outing; both P < .001), while other kinematic measures remained stable.

MLB pitchers who required arthroscopic capsulolabral repair demonstrated a pitch profile characterized by higher velocity and spin coupled with reduced pitch-to-pitch variability. Progressive fastball and breaking ball velocity decline was the clearest marker of impending injury, highlighting a measurable preinjury signature that may inform early detection and intervention.