Table 5

Characteristics of included studies

Study	Study design	Risk factors examined	Outcome measures	Significant risk factor identified	Statistical figures	Non-significant potential risk factors	Sport and sample size (with n injured)
Arnason et al3	Prospective cohort study	Anthropometrics* flexibility, leg extension power, jump height, peak O₂ uptake, joint stability and history of previous injury	Questionnaire, peak O₂ uptake, body composition, power testing, jump, flexibility, and ankle and knee stability tests and injury reports	Previous groin injury Decreased hip Abd ROM Age (older players)	OR=7.3, p=0.001 OR=0.9, p=0.05 OR=0.9, p=0.05	Height Weight Body fat, BMI Power Peak O₂ uptake Flexibility	306 professional soccer players tested, 201 (82%) attained lower limb injuries, 13% were groin injuries
Engebretsen et al21	Prospective cohort study	Anthropometrics*history of groin injury, function scores, clinical examination, and isometric groin strength	Counter-movement jumps, 40 m sprint tests, an isometric adductor strength test, a clinical examination and a questionnaire	Previous groin injury Weak hip adductors	OR=2.6, 95% CI 1.1 to 6.11 OR=4.28, 95% CI 1.31–14.0	Countermovement jump test 40 m sprint test Anthropometrics*Clinical examination† Player experience GrOS total score	508 amateur soccer players, 61 groin injuries were registered
Gabbe et al5	Retrospective cohort study	Anthropometrics*demographic information and previous history of hip/groin injury	The number of hip/groin injuries resulting in ≥1 missed ARF game, over 7 seasons	Previous groin/hip injury	IRR=6.24 95% CI 4.43 to 8.77	Age, BM Height	500 ARF players, 159 (32%) sustained groin/hip injuries
Hagglund et al22	Prospective cohort study	Anthropometrics* and injury data	Injury report sheet (injury location, severity, loss of match and training time, previous injuries) per player	Previous groin/hip injury	HR=2.4 95% CI 1.2 to 4.6 p<0.01	Anthropometrics*	525 elite soccer players tested over 2 seasons, 206 groin/hip injuries recorded
Le Gall et al23	Prospective, observational cohort study	Investigate injury according to biological maturity and chronological age	Skeletal maturity was measured using the Greulich-Pyle method (1959) with players injury (type, incidence, severity and distribution)	Early maturing players	Post hoc=early (0.9) vs normal (0.44) vs late (0.08) maturing p=0.002	Age	233 players over 10 seasons, no figure of groin/hip injuries was available
O'Connor 12	Prospective cohort study	Anthropometric data‡, Kinanthropometric data (sum of skinfolds and femur bone diameter), peak torque, work, power, endurance ratios and peak torque ratios of the hip abductors and adductors and knee flexors and extensors, hip abduction, adduction, internal and external hip rotation ROM, hamstring and groin flexibility	Use of a questionnaire for Anthropometric data, Kinanthropometric measures, A Cybex 340 isokinetic dynamometer, ROM measures, FABER test and Splits	Abd and adduction with rotation peak torque Angle of adduction and abd with rotation peak torque Strength ratio of hip muscle groups Bilateral difference in extension peak torque Smaller femur diameter Higher BM Older age	WL=0.94, p=0.02 WL=0.76, p<0.001 Not available Not available WL=0.89, p=0.001 WL=0.96, p<0.05 p<0.05	Height Body composition Skinfolds Player experience Peak torque, work, power, endurance ratios and peak torque ratios of the hip abductors and adductors in other positions Hip abduction, adduction, internal and external hip rotation ROM Groin flexibility	100 professional rugby league players, 23% sustained groin injuries
Verrall et al24	Prospective cohort study	Anthropometrics*, hip joint internal and external ROM and incidence of groin pain	Player questionnaire, goniometer and team doctor record sheets	Lower body weight Decreased total hip ROM	IRR=0.92, p=0.004 95% CI 0.87 to 0.97 IRR=0.9, p=0.03 95% CI 0.83 to 0.99	Age Height Dominant and non-dominant leg internal and external rotation	29 ARF players, 4 developed chronic groin injury

*Anthropometrics includes: height, weight, age and BMI.
†Clinical examination includes: external rotation in the hip joint (painful or not), functional testing of rectal abdominal muscles (painful or not) and strength of iliopsoas muscles (weak or not weak).
‡Anthropometric data includes: height, weight, age, body composition, playing position, experience, ability level, weight training experience and emphasis on leg and hip muscles.
ARF, Australian Rules Football; BMI, body mass index; IRR, incident rate ratio; ROM, range of motion; WL, Wilks’ λ.