Background Shoulder injuries are common among handball players and are dominated by overuse characteristics.

Objective Assess the effect of three previously identified risk factors for shoulder problems (reduced glenohumeral rotation, external rotation weakness and scapula dyskinesis).

Design Prospective cohort.

Setting Twenty-three handball teams (12 male; 11 female) from the two upper divisions in Norway followed for one competitive season (7 months).

Participants Of 333 players with a team contract, 329 (age 17–47) entered the study (168 male; 161 female); 39 of these dropped out (21 male; 18 female).

Assessment of Risk Factors Prior to the 2014–2015 season we assessed glenohumeral internal and external rotation range of motion, isometric internal and external rotation, as well as scapular dyskinesis.

Main Outcome Measurements Prevalence and severity of shoulder problems registered monthly using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. We used the average severity score for each player as the outcome measure in a multivariable logistic regression model to investigate associations between candidate risk factors and shoulder injury.

Results The average season prevalence of shoulder problems was 20% (95% CI 15% to 26%) among men and 26% (95% CI 26% to 27%) among women; the average prevalence of substantial problems was 7% (95% CI 6% to 7%) and 9% (95% CI 8% to 11%) among men and women, respectively. Significant associations were found between internal rotation motion (OR 1.16 per 5° change, 95% CI 1.00 to 1.34) and isometric external:internal rotation strength ratio <80% (OR 3.17, 95% CI 1.01 to 9) and shoulder injury. Scapula dyskinesis was not associated with shoulder injury (OR 1.36, 95% CI 0.41 to 4.50).

Conclusions This study confirms that external rotation weakness is associated with shoulder injury and should be incorporated in injury prevention programmes, while exercises targeting internal rotation motion and scapula dyskinesis should be excluded.