A comprehensive systematic review has identified five significant risk factors associated with new onset of shoulder pain and injury among athletes: range of motion abnormalities, reduced strength, history of local/regional musculoskeletal pain, previous injury, and training load.

In the study, published in the International Journal of Sports Physical Therapy, investigators from the University of Indianapolis and several other institutions analyzed data from 19 studies comprising 7,802 athletes across multiple sports, including baseball, handball, swimming, tennis, military activities, cricket, and American football.

"Many risk factors are easily objectifiable and modifiable, which may help in developing shoulder injury mitigation strategies,” lead study author Paul Salamh, PT, DPT, PhD, and colleagues noted. "Three of the five significant risk factors for injury can be identified by objective prescreening measures. While previous pain and injury cannot be mitigated, training loads should be closely monitored and adapted according to other risk factors and the athlete’s response," they added.

The investigators conducted a systematic review following PRISMA guidelines, searching PubMed, Embase, AMED, CINAHL, and EmCare databases. They included studies where athletes were initially pain free at baseline, with shoulder or arm pain originating from musculoskeletal shoulder issues, and risk factors captured prospectively. The studies were required to report relative risk (RR), odds ratios (OR), and/or hazard ratios (HR) with follow-up periods of at least 6 months to be included.

The Quality in Prognosis Studies (QUIPS) tool was used for risk of bias assessment. Thirteen studies received an overall rating of low risk of bias, whereas six were rated as moderate, with none classified as high risk.

The review revealed that risk factors varied significantly by sport:

• Range of Motion (ROM): Both increased and decreased ROM in certain movements increased shoulder injury risk, depending on the sport and sometimes sex. Among handball players, for instance, a difference of more than 7.5° in external shoulder ROM on the dominant throwing shoulder (OR = 4.1 [1.1–15.4]) increased injury risk. In swimming, both low shoulder external rotation (less than 93°) and high external rotation (greater than or equal to 100°) increased injury risk (low: OR = 11.1 [2.4–51.6]; high: OR = 5.9 [1.3–28.05]).
• Strength: Decreased dominant shoulder isometric absolute strength (OR = 10.70 [1.2–95.6] per 10 N) and body weight normalized strength (OR = 1.2 [1.0–1.4] per 0.1 N/kg) increased shoulder injury risk in handball players. Among professional baseball pitchers, asymmetric hip strength demonstrated increased risk of shoulder injuries (RR = 1.24 [1.06–1.46]).
• Pain History and Previous Injury: Youth baseball pitchers with a history of shoulder pain (OR = 3.34 [2.16–5.17]) or elbow pain (OR = 1.53 [1.00–2.31]) showed increased risk of sustaining a shoulder injury. In professional baseball pitchers, a previous trunk or lower extremity injury increased the risk of shoulder injury (HR = 2.6 [1.2–5.6]), whereas a previous shoulder injury significantly increased the risk of subsequent shoulder injury (HR = 9.3 [1.1–83]).
• Training Load: Multiple sports showed associations between training load and injury risk. Increased acute workload ratio increased shoulder injury risk (OR = 4.31 [1.001–18.537]) in competitive swimmers. Among tennis players, each workload spike in competition (hazard risk ratio [HRR] = 1.26 [1.15–1.39]), fitness training (HRR = 1.18 [1.09–1.27]), and training/competition (HRR = 1.22 [1.12–1.34]) increased shoulder injury hazard.

The investigators also found that incorporating shoulder injury prevention programs reduced the risk (HRR = 0.44 [0.29-0.68]) of shoulder injuries in handball players, suggesting potential efficacy of targeted interventions.

The investigators highlighted inconsistencies in how injury and pain are defined within the studies as a significant limitation in this research area. They proposed several considerations for future research, including using consistent definitions of injury and pain, clearly differentiating between pain and injury, separating shoulder and elbow data, and utilizing valid and reliable methods to measure risk factors.

“There is a clear need to identify and understand risk factors associated with shoulder pain and injury in athletes who participate in overhead sports to effectively develop and implement shoulder-specific injury prevention programs,” the study authors stated. “Injury prevention programs should account for the unique demands of each sport and, in some instances, individual positions within a given sport,” they concluded.

The authors reported no conflicts of interest