Abstract
Purpose
To evaluate the incidence of pitcher injuries 2 years after implementation of the Major League Baseball (MLB) pitch clock.
Methods
Injury data were collected for the 2021, 2022, 2023, and 2024 MLB seasons using the fangraphs.com injury database. The incidence rate ratio was calculated to compare the injury rate for the 2024 season with that for each of the 2021, 2022, and 2023 seasons. Data were pooled for the pre- and post-pitch clock seasons and were compared in similar fashion to the individual seasons using the incidence rate ratio. The z test for proportions was used to determine significance.
Results
The 2024 MLB season, with 366 overall injuries, showed a decrease in the overall number of injuries compared with the 2021 season, which had 467 overall injuries (P < .001), and the 2022 season, which had 461 overall injuries (P < .001). The 2024 season, with 61 lower-extremity injuries, showed a decrease in the number of lower-extremity injuries compared with the 2021 season, which had 104 lower-extremity injuries (P = .001), and the 2022 season, which had 87 lower-extremity injuries (P = .03). The 2024 season, with 55 torso injuries, showed a decrease in the number of torso injuries compared with the 2022 season, which had 75 torso injuries (P = .04). The 2024 season, which had 62 flexor tendon/forearm injuries, revealed a statistically significant rise in flexor tendon/forearm injuries compared with the 2021 season, with 37 injuries (P = .01); the 2022 season, with 33 injuries (P = .005); and the 2023 season, with 36 injuries (P = .02). There was no statistically significant difference in the number of ulnar collateral ligament operations when the 2024 MLB season (n = 34) was compared with the 2021 season (n = 20), 2022 season (n = 30), and 2023 season (n = 27). When the pre-and post-pitch clock pooled data were compared, there was a significant decrease in overall injuries (P < .001) and lower-extremity injuries (P = .004). This comparison also revealed a significant increase in flexor tendon/forearm injuries (P = .04).
Conclusions
Two years after the implementation of the MLB pitch clock, there was a decrease in the incidence of overall injury rates and lower-extremity injuries. There remained no associated increase in ulnar collateral ligament operations 2 years after implementation. However, the pre- versus post-pitch clock comparison showed a rise in flexor tendon and forearm injuries in the 2024 season.
Level of Evidence
Level III, retrospective cohort study.
Ulnar collateral ligament (UCL) injuries of the elbow remain one of the most devastating injuries for Major League Baseball (MLB) pitchers.1 Pitchers at the professional level typically undergo surgical treatment for UCL tears to return to pitching.2,3 In the past, a UCL tear was considered a career-ending injury. However, through advancements in surgery and rehabilitation, players in the modern game may return after this injury and have successful careers.4, 5, 6 Traditional UCL reconstruction typically leaves pitchers out of the game for 12 to 16 months. A recent advancement in UCL surgery has been a UCL repair technique using suture augmentation.4,5,7 This surgical technique has grown in popularity because it may decrease the return-to-play time by a few months.4,5,7 Regardless of surgical technique, surgical treatment of UCL tears can lead to players missing 1 or 2 seasons.8 This missed time can have a major impact on players’ careers and a large impact on the organization for which they play.4, 5, 6
The beginning of the 2024 MLB season saw several star pitchers tear the UCL in the pitching elbow, subsequently resulting in UCL surgery for these players.9 Many theories have been proposed to explain UCL injuries,3,10, 11, 12, 13, 14, 15 including increases in pitch spin and velocity and the introduction of the “sweeper” breaking ball.11 However, the MLB pitch clock remains at the forefront regarding the perceived rise in UCL injuries among MLB pitchers.10
In 2023, MLB implemented the pitch clock to increase the pace of play in MLB games.16 The pitch clock provides pitchers with 15 seconds between pitches with no runners on base and 20 seconds between pitches with runners on base before they must deliver a pitch.16 When the pitch clock was introduced in Minor League Baseball, Sonne and Keir17 (2016) hypothesized that these rule changes would lead to increased injuries. This peer-reviewed publication suggested that elbow injuries would rise owing to decreased recovery and elevated fatigue of the flexor pronator mass in the authors’ predictive model of muscle fatigue for Minor League Baseball pitchers.17 They hypothesized that this would lead to reduced effectiveness of the flexor pronator mass, which may reduce active contributions to joint rotational stiffness, and lead to increased strain on the UCL. However, a 2024 study evaluated the effect of the pitch clock on the incidence of injuries in MLB pitchers at 1 year after implementation and found no difference in the incidence of UCL injuries, elbow injuries, or flexor tendon injuries compared with the prior 2 seasons.18 The study ultimately showed that the pitch clock had no effect after 1 year. However, this study only evaluated data 1 year after pitch clock implementation, and it is unclear whether the potential effects predicted by Sonne and Keir are cumulative over time or whether they affect pitchers who throw more innings or more frequently. With the continued perceived rise in injuries in 2024, as well as the previous theories on the pitch clock, the pitch clock remains at the forefront of the discussion regarding UCL injuries.19
The purpose of this study was to evaluate the incidence of pitcher injuries 2 years after implementation of the MLB pitch clock. We hypothesized that the incidence of UCL injuries in MLB pitchers would remain consistent 2 years after the introduction of the MLB pitch clock, with a persistent decrease in the overall number of injuries.
Methods
Study Design
This research activity was determined to be exempt or excluded from institutional review board oversight in accordance with current regulations and institutional policy. Injury data were collected and compiled from the fangraphs.com injury report database (Fangraphs, Arlington, VA), which has been a commonly used source for MLB injury analysis studies in the recent literature.18,20, 21, 22 Fangraphs.com states that all MLB and Minor League Baseball data are provided directly by MLB.20 The study design and methodology were adapted from recent studies that evaluated MLB injury incidence.18,21,23 Injury data were collected for the 2021, 2022, 2023, and 2024 MLB seasons. The 2023 season was the first season in which the MLB implemented the pitch clock, and the 2024 season was the second. Seasons before 2021 were not included owing to the 2020 season being shortened by COVID-19 (coronavirus disease 2019), leading to an influence on the incidence of injuries.18,21,22 Injuries were included if they occurred in the time frame between opening day and the final day of the regular season to produce a consistent period and an accurate assessment of average game exposure. Illnesses and non-neuromusculoskeletal complaints were excluded from the data.23 Data were compiled into the following major anatomic categories: total injuries, upper extremity, lower extremity, torso, head/neck, and undisclosed. Detailed subgroup categories of the major categories were investigated, including elbow-specific injury analysis.
Data Analysis
Data analysis methods were adapted from the original pitch clock study and followed the methods of MLB injury analysis studies in the recent literature.18,22,23 The incidence rate (IR) was calculated for each category using average game exposure per 1,000 athletes.18,22,23 Average game exposure was calculated by multiplying the number of pitchers on the roster (13) by the total games played in the season (162) by the number of teams (30).18,22,23 This calculation yielded an average game exposure value of 63,180. The IR was calculated as the number of injuries divided by the average game exposure and multiplied by 1,000.18,22,23 To compare the 2024 season versus each of the 2021, 2022, and 2023 seasons, the incidence rate ratio (IRR) was calculated by dividing the IR of the 2024 season by the IR of the season of comparison.18,22,23 The data were then pooled for the 2 seasons before and 2 seasons after pitch clock implementation to reduce potential year-to-year variations in injuries. Average game exposure was determined for the total exposure of 2 seasons,21 which yielded an average game exposure value of 126,630 for both the pre- and post-pitch clock cohorts. The IR and IRR were calculated for the pre- and post-pitch clock data, and comparisons were completed in a similar fashion to the individual seasons.21 Ninety-five percent confidence intervals (CIs) were calculated for each IRR comparison for every injury that was compared between cohorts. The z test for proportions was used to determine whether significant differences existed between the injury incidences.18,22,23
Results
Total Number of Injuries
The total number of injuries was 467, 461, 393, and 366 for the 2021, 2022, 2023, and 2024 seasons, respectively. The 2024 seasons showed the highest total number of elbow and forearm injuries, with 128. The lowest number of elbow and forearm injuries occurred in 2021, with 107. The lowest number of lower-extremity injuries occurred in 2024, with 61. The highest number of lower-extremity injuries occurred in 2021, with 104. The 2024 season also showed the lowest number of torso injuries, with 55. The highest number of UCL operations occurred in 2024, with 34 UCL operations. The lowest number of UCL operations was seen in 2021, with 20 (Table 1).
Table 1.
Total Number of Injuries by Category
| 2021 Season | 2022 Season | 2023 Season | 2024 Season | |
|---|---|---|---|---|
| Major anatomic categories | ||||
| Total injuries | 467 | 461 | 393 | 366 |
| Upper extremity | 269 | 233 | 232 | 242 |
| Lower extremity | 104 | 87 | 80 | 61 |
| Head/neck | 13 | 13 | 12 | 8 |
| Torso | 75 | 78 | 64 | 55 |
| Undisclosed | 6 | 50 | 5 | 0 |
| Subgroup anatomic categories | ||||
| Elbow/forearm | 107 | 109 | 122 | 128 |
| Shoulder | 103 | 87 | 76 | 88 |
| Groin/quadriceps | 24 | 16 | 7 | 14 |
| Hamstring | 24 | 12 | 19 | 11 |
| Knee | 19 | 17 | 15 | 14 |
| Foot/ankle | 18 | 16 | 13 | 7 |
| Torso | 75 | 89 | 64 | 55 |
| Head/neck | 13 | 13 | 12 | 8 |
| Calf/lower leg/shin | 11 | 12 | 13 | 6 |
| Biceps/triceps | 18 | 16 | 21 | 11 |
| Hand/wrist | 41 | 21 | 13 | 15 |
| Hip/gluteus | 8 | 14 | 13 | 9 |
| Elbow-specific categories | ||||
| UCL surgery | 20 | 30 | 27 | 34 |
| Flexor tendon/forearm injury | 37 | 33 | 36 | 62 |
| Other elbow | 50 | 46 | 59 | 32 |
UCL, ulnar collateral ligament.
2021 IR Versus 2024 IR
Comparison of the 2024 season versus the 2021 season showed a statistically significant decrease in total injuries (IRR, 0.78; 95% CI, 0.68-0.90; P < .001). The 2024 season had 366 total injuries, whereas the 2021 season had 467. The number of lower-extremity injuries during the 2024 season was also significantly lower (IRR, 0.59; 95% CI, 0.43-0.80; P = .001) than in 2021. The 2024 season had 61 lower-extremity injuries, whereas the 2021 seasons had 104 lower-extremity injuries. There was no significant change in injuries in the 2024 season compared with the 2021 season for the remaining major categories. When we compared anatomic subgroups for the 2024 and 2021 seasons, significant decreases were observed in hamstring (IRR, 0.46; 95% CI, 0.22-0.94; P = .03), foot/ankle (IRR, 0.39; 95% CI, 0.16-0.93; P = .04), and hand/wrist (IRR, 0.37; 95% CI, 0.20-0.66; P = .002) injuries for the 2024 season. No significant difference was noted in any other anatomic subgroup. Elbow-specific comparison between the 2024 and 2021 seasons revealed a statistically significant increase in flexor tendon/forearm injuries (P = .01). No statistically significant change in UCL operations or other elbow injuries (e.g., inflammation) was noted (P = .06) (Table 2).
Table 2.
Injury Comparison of 2024 MLB Season Versus 2021 MLB Season
| Injuries | 2021 IR | 2024 IR | IRR (95% CI): 2024 vs 2021 | P Value |
|---|---|---|---|---|
| Total injuries | 7.39 | 5.79 | 0.78 (0.68-0.90) | <.001∗ |
| Upper extremity | 4.26 | 3.83 | 0.90 (0.75-1.07) | .18 |
| Lower extremity | 1.65 | 0.97 | 0.59 (0.43-0.80) | .001∗ |
| Head/neck | 0.21 | 0.13 | 0.62 (0.26-1.48) | .28 |
| Torso | 1.19 | 0.87 | 0.73 (0.52-1.04) | .07 |
| Undisclosed | 0.09 | 0.00 | 0.00 (0.00-0.00) | 0 |
| Subgroup anatomic categories | ||||
| Elbow/forearm | 1.69 | 2.03 | 1.20 (0.93-1.55) | .22 |
| Shoulder | 1.63 | 1.39 | 0.85 (0.64-1.14) | .27 |
| Groin/quadriceps | 0.38 | 0.22 | 0.58 (0.30-1.13) | .12 |
| Hamstring | 0.38 | 0.17 | 0.46 (0.22-0.94) | .03∗ |
| Knee | 0.30 | 0.22 | 0.74 (0.37-1.47) | .36 |
| Foot/ankle | 0.28 | 0.11 | 0.39 (0.16-0.93) | .04∗ |
| Torso | 1.19 | 0.87 | 0.73 (0.52-1.04) | .07 |
| Head/neck | 0.21 | 0.13 | 0.62 (0.24-1.48) | .28 |
| Calf/lower leg/shin | 0.17 | 0.09 | 0.55 (0.20-1.47) | .23 |
| Biceps/triceps | 0.28 | 0.17 | 0.61 (0.29-1.29) | .21 |
| Hand/wrist | 0.65 | 0.24 | 0.37 (0.20-0.66) | .002∗ |
| Hip/gluteus | 0.13 | 0.14 | 1.12 (0.43-2.92) | .80 |
| Elbow-specific categories | ||||
| UCL surgery | 0.32 | 0.54 | 1.70 (0.98-2.95) | .06 |
| Flexor tendon/forearm injury | 0.59 | 0.98 | 1.68 (1.12-2.52) | .01∗ |
| Other elbow | 0.79 | 0.51 | 0.64 (0.41-1.00) | .05 |
CI, confidence interval; IR, incidence rate; IRR, incidence rate ratio; MLB, Major League Baseball; UCL, ulnar collateral ligament.
Statistically significant.
2022 IR Versus 2024 IR
Comparison of the 2024 season versus the 2022 season showed a statistically significant decrease in the total number of injuries (IRR, 0.79; 95% CI, 0.69-0.91; P < .001). The 2024 season had 366 total injuries, whereas the 2022 season had 461. A statistically significant decrease in lower-extremity (IRR, 0.70; 95% CI, 0.41-0.97; P = .03) and torso (IRR, 0.71; 95% CI, 0.50-0.99; P = .04) injuries was noted between the 2024 and 2022 seasons. There was no significant change in injuries for the remaining categories in the 2024 season versus the 2022 season. Anatomic subgroup analysis of the 2024 and 2022 seasons showed a statistically significant decrease in torso injuries (IRR, 0.71; 95% CI, 0.50-0.99; P = .04). No significant difference was noted in any other anatomic subgroup. Elbow-specific injury comparison of the 2024 season with the 2022 season showed a statistically significant increase in flexor tendon/forearm injuries (IRR, 1.88; 95% CI, 1.23-2.87; P = .005) (Table 3).
Table 3.
Injury Comparison of 2024 MLB Season Versus 2022 MLB Season
| Injuries | 2022 IR | 2024 IR | IRR (95% CI): 2024 vs 2022 | P Value |
|---|---|---|---|---|
| Total injuries | 7.30 | 5.79 | 0.79 (0.69-0.91) | <.001∗ |
| Upper extremity | 3.69 | 3.83 | 1.04 (0.87-1.24) | .66 |
| Lower extremity | 1.38 | 0.97 | 0.70 (0.41-0.97) | .03∗ |
| Head/neck | 0.21 | 0.13 | 0.62 (0.26-1.48) | .28 |
| Torso | 1.23 | 0.87 | 0.71 (0.50-0.99) | .04∗ |
| Undisclosed | 0.79 | 0.00 | 0.00 (0.00-0.00) | 0 |
| Subgroup anatomic categories | ||||
| Elbow/forearm | 1.73 | 2.03 | 1.17 (0.91-1.52) | .22 |
| Shoulder | 1.38 | 1.39 | 1.01 (0.75-1.36) | >.999 |
| Groin/quadriceps | 0.25 | 0.22 | 0.87 (0.43-1.79) | .74 |
| Hamstring | 0.19 | 0.17 | 0.92 (0.40-1.79) | .85 |
| Knee | 0.27 | 0.22 | 0.82 (0.41-1.67) | .58 |
| Foot/ankle | 0.25 | 0.11 | 0.44 (0.18-1.06) | .07 |
| Torso | 1.23 | 0.87 | 0.71 (0.50-0.99) | .04∗ |
| Head/neck | 0.21 | 0.13 | 0.62 (0.26-1.48) | .28 |
| Calf/lower leg/shin | 0.19 | 0.09 | 0.50 (0.19-1.33) | .17 |
| Biceps/triceps | 0.25 | 0.17 | 0.69 (0.32-1.48) | .21 |
| Hand/wrist | 0.33 | 0.24 | 0.71 (0.37-1.39) | .34 |
| Hip/gluteus | 0.22 | 0.14 | 0.64 (0.28-1.49) | .30 |
| Elbow-specific categories | ||||
| UCL surgery | 0.47 | 0.54 | 1.13 (0.69-1.85) | .63 |
| Flexor tendon/forearm injury | 0.52 | 0.98 | 1.88 (1.23-2.87) | .005∗ |
| Other elbow | 0.73 | 0.51 | 0.70 (0.44-1.09) | .12 |
CI, confidence interval; IR, incidence rate; IRR, incidence rate ratio; MLB, Major League Baseball; UCL, ulnar collateral ligament.
Statistically significant.
2023 IR Versus 2024 IR
No statistically significant change in the total number of injuries was noted on comparison of the 2024 and 2023 seasons (P = .27). The 2024 season had a total of 367 total injuries, whereas the 2023 season had 293. There was no significant change in injuries in 2024 versus 2023 for the remaining categories. Elbow-specific injury comparison of the 2024 and 2023 seasons revealed a statistically significant increase in flexor tendon/forearm injuries (IRR, 1.72; 95% CI, 1.14-2.60; P = .02). The 2024 season had 62 flexor tendon/forearm injuries, whereas 2023 season had 36. The 2024 season had a significant decrease in other elbow injuries (IRR, 0.54; 95% CI, 0.35-0.83; P = .006). No statistically significant change in UCL operations was noted (P = .35) (Table 4).
Table 4.
Injury Comparison of 2024 MLB Season Versus 2023 MLB Season
| Injuries | 2023 IR | 2024 IR | IRR (95% CI): 2024 vs 2023 | P Value |
|---|---|---|---|---|
| Total injuries | 6.22 | 5.79 | 0.93 (0.81-1.07) | .27 |
| Upper extremity | 3.67 | 3.83 | 1.04 (0.87-1.25) | .66 |
| Lower extremity | 1.27 | 0.97 | 0.76 (0.55-1.06) | .10 |
| Head/neck | 0.19 | 0.13 | 0.67 (0.27-1.63) | .38 |
| Torso | 1.01 | 0.87 | 0.86 (0.60-1.23) | .38 |
| Undisclosed | 0.08 | 0.00 | 0.00 (0.00-0.00) | 0 |
| Subgroup anatomic categories | ||||
| Elbow/forearm | 1.93 | 2.03 | 1.05 (0.82-1.34) | .75 |
| Shoulder | 1.20 | 1.39 | 1.16 (0.85-1.57) | .31 |
| Groin/quadriceps | 0.11 | 0.22 | 2.00 (0.81-4.96) | .14 |
| Hamstring | 0.30 | 0.17 | 0.58 (0.28-1.22) | .17 |
| Knee | 0.24 | 0.22 | 0.93 (0.45-1.93) | .83 |
| Foot/ankle | 0.21 | 0.11 | 0.54 (0.21-1.35) | .20 |
| Torso | 1.01 | 0.87 | 0.86 (0.60-1.23) | .38 |
| Head/neck | 0.19 | 0.13 | 0.67 (0.27-1.63) | .38 |
| Calf/lower leg/shin | 0.21 | 0.09 | 0.46 (0.18-1.21) | .14 |
| Biceps/triceps | 0.33 | 0.17 | 0.52 (0.25-1.09) | .08 |
| Hand/wrist | 0.21 | 0.24 | 1.15 (0.55-2.42) | .67 |
| Hip/gluteus | 0.21 | 0.14 | 0.69 (0.30-1.62) | .41 |
| Elbow-specific categories | ||||
| UCL surgery | 0.43 | 0.54 | 1.26 (0.76-2.08) | .35 |
| Flexor tendon/forearm injury | 0.57 | 0.98 | 1.72 (1.14-2.60) | .02∗ |
| Other elbow | 0.93 | 0.51 | 0.54 (0.35-0.83) | .006∗ |
CI, confidence interval; IR, incidence rate; IRR, incidence rate ratio; MLB, Major League Baseball; UCL, ulnar collateral ligament.
Statistically significant.
Pre- Versus Post-Pitch Clock Pooled Analysis
When the 2 seasons prior to pitch clock implementation and the 2 seasons after pitch clock implementation were compared, there was a statistically significant decrease in the total number of injuries (IRR, 0.82; 95% CI, 0.74-0.90; P < .001). There was also a statistically significant decrease in lower-extremity (IRR, 0.74; 95% CI, 0.59-0.92; P = .004), torso (IRR, 0.78; 95% CI, 0.61-0.99; P = .04), undisclosed (IRR, 0.47; 95% CI, 0.04-0.22; P < .001), groin/quadriceps (IRR, 0.53; 95% CI, 0.31-0.89; P = .02), and hand/wrist (IRR, 0.45; 95% CI, 0.29-0.71; P < .001) injuries. Elbow-specific injury comparison of the 2 seasons after pitch clock implementation versus the 2 seasons before pitch clock implementation showed a statistically significant increase in flexor tendon/forearm injuries (IRR, 1.40; 95% CI, 1.03-1.90; P = .04). There was no significant difference in the number of UCL operations when the pre- and post-pitch clock data were compared. There was also no significant change in injuries for the remaining categories when the pre- and post-pitch clock data were compared (Table 5).
Table 5.
Injury Comparison of Pooled Data of 2 Pre–Pitch Clock MLB Seasons Versus Pooled Data of 2 Post–Pitch Clock MLB Seasons
| Injuries | Before Pitch Clock Implementation | After Pitch Clock Implementation | IRR (95% CI): Before vs After Implementation | P Value |
|---|---|---|---|---|
| Total injuries | 7.34 | 6.01 | 0.82 (0.74-0.90) | <.001∗ |
| Upper extremity | 3.97 | 3.75 | 0.84 (0.83-1.07) | .21 |
| Lower extremity | 1.51 | 1.12 | 0.74 (0.59-0.92) | .004∗ |
| Head/neck | 0.21 | 0.16 | 0.77 (0.43-1.38) | .34 |
| Torso | 1.21 | 0.94 | 0.78 (0.61-0.99) | .04∗ |
| Undisclosed | 0.44 | 0.04 | 0.47 (0.04-0.22) | <.001∗ |
| Subgroup anatomic categories | ||||
| Elbow/forearm | 1.71 | 1.98 | 1.16 (0.96-1.39) | .08 |
| Shoulder | 1.50 | 1.30 | 0.86 (0.70-1.06) | .13 |
| Groin/quadriceps | 0.32 | 0.17 | 0.53 (0.31-0.89) | .02∗ |
| Hamstring | 0.28 | 0.24 | 0.83 (0.51-1.35) | .42 |
| Knee | 0.28 | 0.23 | 0.81 (0.49-1.31) | .42 |
| Foot/ankle | 0.27 | 0.16 | 0.59 (0.34-1.02) | .06 |
| Torso | 1.21 | 0.94 | 0.78 (0.61-0.99) | .04∗ |
| Head/neck | 0.21 | 0.16 | 0.77 (0.43-1.38) | .34 |
| Calf/lower leg/shin | 0.18 | 0.15 | 0.83 (0.45-1.52) | .51 |
| Biceps/triceps | 0.27 | 0.25 | 0.94 (0.58-1.53) | .75 |
| Hand/wrist | 0.49 | 0.22 | 0.45 (0.29-0.71) | <.001∗ |
| Hip/gluteus | 0.17 | 0.17 | 1.00 (0.55-1.81) | >.999 |
| Elbow-specific categories | ||||
| UCL surgery | 0.40 | 0.48 | 1.22 (0.84-1.77) | .29 |
| Flexor tendon/forearm injury | 0.55 | 0.78 | 1.40 (1.03-1.90) | .04∗ |
| Other elbow | 0.76 | 0.72 | 0.95 (0.71-1.26) | .79 |
CI, confidence interval; IRR, incidence rate ratio; MLB, Major League Baseball; UCL, ulnar collateral ligament.
Statistically significant.
Discussion
The most important finding of this study was that the total number of injuries and lower-extremity injuries decreased significantly in the 2024 MLB season compared with the 2021 and 2022 seasons. There was also a decrease in the total number of injuries in the post-pitch clock cohort in the pre- versus post-pitch clock pooled data analysis. In addition, the 2024 season showed a decrease in torso injuries when compared with the 2022 season. Concerning elbow-specific pathology, the 2024 season showed the highest number of UCL operations. However, there remained no significant difference in the level of UCL operations when comparing 2024 with the previous seasons. One concerning trend that emerged regarding elbow-specific pathology was that the number of flexor tendon and forearm injuries showed a statistically significant increase in 2024 compared with all previous seasons. This rise in flexor tendon and forearm injuries was also seen in the post-pitch clock cohort in the pooled data analysis.
This study found a decrease in the number of total injuries and lower-extremity injuries when comparing the 2024 MLB season versus the 2021 and 2022 seasons. Likewise, the results showed a decreased number of torso injuries when comparing the 2024 and 2022 seasons. These decreases in injuries were also seen in the pooled analysis. A study of position players in 2024 found a decrease in total injuries and some lower-extremity injuries in the position player population 1 year after the implementation of the pitch clock.24 However, at this time, it is unclear if the pitch clock is the driving factor for these decreases in overall injuries and, specifically, lower-extremity injuries. There could be numerous factors that are leading to this drop in injuries. Future studies will be needed to determine whether this trend persists in the position player and pitcher populations over time-and whether a single driving factor can be identified for these trends.
Our study found increased flexor tendon and forearm injuries when comparing the 2024 season versus the 2023, 2022, and 2021 seasons. This rise in flexor tendon and forearm injuries was also seen in the post-pitch clock cohort during the pre- versus post-pitch clock pooled data analysis. Before implementation of the pitch clock in Minor League Baseball, it was believed that there would be increased UCL injuries due to flexor tendon pronator mass fatigue stemming from a decreased recovery time between pitches.17 Sonne and Keir17 hypothesized that flexor pronator mass fatigue would lead to decreased effectiveness of this muscle in maintaining joint rotational stiffness, which would lead to increased UCL strain and injury risk. It is unknown whether this effect is cumulative, and it is possible that this effect on the flexor-pronator mass is now beginning to be realized 2 years after the implementation of the pitch clock. The flexor pronator mass is a dynamic stabilizer of the elbow joint, and it helps to resist valgus forces on the elbow. The UCL is the primary restraint to valgus forces during throwing, and this function of the flexor pronator mass helps to reduce strain on the UCL.25 Because flexor tendon injuries have been strongly associated with UCL injuries,26,27 it is paramount to determine whether this rise in flexor tendon injuries ultimately leads to more UCL operations over the next several seasons. The rise in flexor tendon injuries could be a potential alert that UCL operations may rise over the subsequent seasons. This is why future follow-up studies, particularly longitudinal evaluations at 5-year follow-up, are critical to evaluate whether the 2024 season was an outlier or a predecessor for future injuries.
The MLB pitch clock has been shown to have some positive effects in decreasing the incidence of lower-extremity injuries and the total number of injuries in both position players and pitchers. This benefit may show that the duration of time spent on an activity is equally important for injury prevention, as duration of activity acts as a component of overall workload. Longitudinal effects of the MLB pitch clock beyond 2 years remain to be seen.
Future follow-up studies will be critical to understand the full effects of the MLB pitch clock. If a reduction in overall injuries and lower-extremity injuries persists, it would be beneficial to have some aspect of the pitch clock in place. However, if there is a rise in UCL operations, it may be beneficial to adjust the pitch clock length to allow for better recovery of the flexor-pronator complex for pitchers. This research may enable MLB and collegiate rule makers to adjust the rules to create the safest playing environment for pitchers and position players.
Limitations
Several methodologic constraints affected this research. First, the analysis focused exclusively on regular-season data to maintain consistency, excluding injuries from the spring training, postseason, and off-season periods. This was consistent with previous literature18,24 to produce a consistent time frame. Second, this study did not evaluate injuries at the Minor League Baseball level and was strictly limited to the MLB level. Third, there is the potential for reporting bias due to the fact that this study only has 2 years of data since implementation of the pitch clock, and variations may naturally exist year to year. Therefore, the current data set may report outliers that may not fully represent the impact of the pitch clock over time. However, analysis was conducted on pooled data for the 2 seasons before pitch clock implementation and the 2 seasons after implementation to account for potential year-to-year variations. Ultimately, the full effect of the pitch clock and elimination of year-to-year variations may be better seen with a longitudinal analysis. Fourth, there is potential variation in average game exposure. Relief pitchers and starting pitchers may have variations in their actual exposure. For example, relief pitchers may pitch more games but may throw fewer innings. Exposure may also be influenced by a number of factors such as bullpen sessions, catch sessions, or warm-up sessions prior to pitching in a game. Owing to the wide variations, average game exposure standardizes all potential game exposures. All of these throwing variables and workload variations between relief and starting pitchers present a limitation in this study. Finally, this study did not evaluate changes in pitch type, velocity, or other potential factors that have been postulated for the perceived rise in UCL operations.
Conclusions
Two years after the implementation of the MLB pitch clock, there was a decrease in the incidence of overall injury rates and lower-extremity injuries. There remained no associated increase in UCL operations 2 years after implementation. However, the pre- versus post-pitch clock comparison showed a rise in flexor tendon and forearm injuries in the 2024 season.
Disclosures
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: J.T.R. reports a consulting or advisory relationship with Arthrex and has a patent with royalties paid to Arthrex. All other authors (T.B.P., M.W.B., W.S., H.D.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding
This project received no funding. This research was supported (in whole or part) by HCA Healthcare and/or an HCA Healthcare-affiliated entity. The views expressed in this publication represent those of the authors and do not necessarily represent the official views of HCA Healthcare or any affiliated entities.
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