Summary of synthesis of prognostic factors for all injury outcomes with associated GRADE evaluation
| Adapted GRADE criteria | |||||||||||||
| Injury type | Specific Outcomes | Potential prognostic factors | Number of studies | Authors | Effect measure | Univariate Effect size (95% CI) | Multivariate effect size (95% CI) | Study limitations | Consistency of results | Effect size | Precision of results | Publication bias | Overall quality |
| Muscle injuries | Hamstring injuries | Increasing age | 2 | Hagglund et al 36 37 | HR | Figure 2 | 1.1 (1 to 1.2) | Many | No | Small | Imprecise | Likely | Low |
| Increasing age | 2 | Arnason et al,30 Henderson et al 39 | OR | – | Figure 3 | Many | Yes | Small | Precise | Likely | Low | ||
| Previous hamstring injury | 2 | Hagglund et al 36 37 | HR | Figure 2 | Figure 2 | Many | Yes | Moderate | Imprecise | Likely | Low | ||
| Previous hamstring injury | 2 | Arnason et al,30 Fousekis et al 34 | OR | 7.42 (2.9 to 19) | Figure 3 | Very many | No | Variable | Imprecise | Likely | Very low | ||
| Stature (above mean) | 1 | Hagglund et al 37 | HR | 0.82 (0.68 to 1.0) | – | Many | N/A | Small | Imprecise | Likely | Very low | ||
| Previous quadriceps injury | 1 | Hagglund et al 37 | HR | 1.44 (1.08 to 1.93) | – | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Eccentric hamstring strength asymmetries | 1 | Fousekis et al 34 | OR | – | 3.88 (1.13 to 13.23) | Very many | N/A | Moderate | Imprecise | Likely | Low | ||
| BW adjusted eccentric hamstring strength (60 deg/s) | 1 | Van Dyk et al 42 | OR | – | 1.37 (1.01 to 1.85) | Many | N/A | Small | Imprecise | Likely | Very low | ||
| BW adjusted concentric quadriceps strength (60 degree/s) | 1 | Van Dyk et al 42 | OR | – | 1.41 (1.03 to 1.92) | Many | N/A | Small | Imprecise | Likely | Very low | ||
| Active hip flexion ROM (dominant leg) | 1 | Henderson et al 39 | OR | – | 0.77 (0.62 to 0.97) | Many | N/A | Small | Imprecise | Likely | Low | ||
| Increased NCMJ height | 1 | Henderson et al 39 | OR | – | 1.47 (1.02 to 2.12) | Many | N/A | Small | Imprecise | Likely | Low | ||
| Functional leg length asymmetry | 1 | Fousekis et al 34 | OR | – | 3.8 (1.08 to 13.33) | Very many | N/A | Large | Imprecise | Likely | Low | ||
| Position: goalkeeper | 1 | Hagglund et al 37 | HR | 0.11 (0.06 to 0.23) | 0.11 (0.06 to 0.24) | Very many | N/A | Large | Imprecise | Likely | Very low | ||
| Time of season: | |||||||||||||
| September-November | 1 | Hagglund et al 37 | OR | 2.24 (1.34 to 3.74) | 2.16 (1.29 to 3.60) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| December–February | 1 | Hagglund et al 37 | OR | 2.56 (1.54 to 4.26) | 2.55 (1.53 to 4.24) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| March–May | 1 | Hagglund et al 37 | OR | 2.56 (1.54 to 4.28) | 2.49 (1.49 to 4.17) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Playing league matches with ≤4 days recovery | 1 | Bengtsson et al 31 | RR | – | 1.28 (1.06 to 1.56) | Many | N/A | Small | Imprecise | Likely | Very low | ||
| Venue: away match | 1 | Hagglund et al 37 | OR | 0.75 (0.62 to 0.91) | 0.76 (0.63 to 0.92) | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Quadriceps injuries | Previous adductor injury | 1 | Hagglund et al 37 | HR | 1.88 (1.31 to 2.69) | 1.68 (1.16 to 2.41) | Very many | N/A | Small | Imprecise | Likely | Very Low | |
| Previous quadriceps injury | 1 | Hagglund et al 37 | HR | 3.47 (2.49 to 4.84) | 3.1 (2.21 to 4.36) | Very many | N/A | Large | Imprecise | Likely | Very low | ||
| Previous calf injury | 1 | Hagglund et al 37 | HR | 2.08 (1.37 to 3.17) | 1.91 (1.24 to 2.93) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Position: goalkeeper | 1 | Hagglund et al 37 | HR | 0.46 (0.23 to 0.9) | 0.41 (0.2 to 0.82) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Playing league matches with ≤4 days recovery | 1 | Bengtsson et al 31 | RR | – | 1.8 (1.19 to 2.72) | Many | N/A | Small | Imprecise | Likely | Very Low | ||
| Match type: UEFA CL | 1 | Hagglund et al 37 | OR | 0.51 (0.25 to 1.01) | 0.48 (0.24 to 0.97) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Adductor injuries | Previous adductor injury | 1 | Hagglund et al 37 | HR | 1.48 (1.06 to 2.06) | 1.40 (1 to 1.96) | Very many | N/A | Small | Imprecise | Likely | Very low | |
| Position: goalkeeper | 1 | Hagglund et al 37 | HR | 0.58 (0.33 to 0.99) | 0.51 (0.29 to 0.91) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Venue: away match | 1 | Hagglund et al 37 | OR | 0.56 (0.43 to 0.73) | 0.56 (0.43 to 0.73) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Match type: other cup | 1 | Hagglund et al 37 | OR | 0.60 (0.37 to 0.97) | – | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Groin strain injuries | Previous groin strain | 1 | Arnason et al 30 | OR | 5.71 (2 to 15.9) | 7.3 (2.3 to 23.2) | Many | N/A | Large | Imprecise | Likely | Low | |
| Reduced ROM hip abduction | 1 | Arnason et al 30 | OR | – | 0.9 (0.8 to 1) | Many | N/A | Small | Imprecise | Likely | Very Low | ||
| Calf muscle injuries | Previous calf muscle injury | 1 | Hagglund et al 37 | HR | 2.83 (1.86 to 4.31) | 2.33 (1.52 to 3.57) | Very many | N/A | Moderate | Imprecise | Likely | Very low | |
| Increasing age | 1 | Hagglund et al 37 | HR | 2.02 (1.45 to 2.82) | 1.93 (1.38 to 2.71) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Previous adductor injury | 1 | Hagglund et al 37 | HR | 1.87 (1.26 to 2.77) | 1.71 (1.15 to 2.55) | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Previous hamstring injury | 1 | Hagglund et al 37 | HR | 2.1 (1.51 to 2.54) | 1.74 (1.24 to 2.44) | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Match type: UEFA CL | 1 | Hagglund et al 37 | OR | 2.43 (1.61 to 3.67) | 2.72 (1.78 to 4.14) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Position: goalkeeper | 1 | Hagglund et al 37 | HR | 0.43 (0.2 to 0.96) | 0.36 (0.16 to 0.82) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Ligament injuries | Ankle sprain | Previous ankle sprain* | 2 | Arnason et al, 30 Faude et al 33 | OR | Figure 4 | Figure 4 | Many | No | Large | Imprecise | Likely | Very low |
| Weight above median | 1 | Fousekis et al 35 | OR | – | 5.72 (1.37 to 23.95) | Many | N/A | Large | Imprecise | Likely | Very low | ||
| BMI > median | 1 | Fousekis et al 35 | OR | – | 8.16 (1.42 to 46.63) | Many | N/A | Large | Imprecise | Likely | Very low | ||
| Eccentric ankle strength asymmetry >15% | 1 | Fousekis et al 35 | OR | – | 8.88 (1.95 to 40.36) | Many | N/A | Large | Imprecise | Likely | Very low | ||
| Playing three matches within4 days | 1 | Carling et al 32 | IRR | 10.4 (1.9 to 57.9) | – | Many | N/A | Large | Imprecise | Likely | Very low | ||
| Knee sprain | Previous knee sprain* | 2 | Arnason et al 30 Faude et al 33 | OR | Figure 4 | Figure 4 | Many | No | Moderate | Imprecise | Likely | Very low | |
| ACL tear | Previous ACL tear† | 1 | Faude et al 33 | OR | – | 5.24 (1.42 to 19.59) | Many | N/A | Large | Imprecise | Likely | Very low | |
| Tendinopathy | Patellar tendinopathy | Age | 1 | Hagglund et al 38 | OR | – | 0.97 (0.93 to 1.01) | Very many | N/A | Small | Imprecise | Likely | Very low |
| Increased body weight (per 5 kg) | 1 | Hagglund et al 38 | OR | – | 1.15 (1 to 1.33) | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Total football exposure hours (per 10 hours increase) | 1 | Hagglund et al 38 | OR | No data | 1.02 (1 to 1.04) | Very many | N/A | Small | Imprecise | Likely | Very low | ||
| Injuries defined by anatomical location | Traumatic knee injuries | Previous ACL injury‡ | 1 | Waldén et al 41 | Rel. R | – | 2.6 (1.1 to 6.7) | Very many | N/A | Moderate | Imprecise | Likely | Very low |
| Previous ACL injury§ | 1 | Waldén et al 41 | Rel. R | – | 2.7 (1.3 to 5.8) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Previous knee injury | 1 | Hagglund et al 36 | HR | – | 3.10 (1.3 to 7.6) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Overuse knee injuries | Previous ACL injury ‡ | 1 | Waldén et al 41 | Rel. R | – | 7.9 (3.4 to 18.5) | Very many | N/A | Large | Imprecise | Likely | Very low | |
| Previous ACL injury§ | 1 | Waldén et al 41 | Rel. R | – | 4.8 (2.0 to 11.2) | Very many | N/A | Large | Imprecise | Likely | Very low | ||
| Thigh injuries | Increased BMI | 1 | Nilstad et al 40 | OR | 1.37 (0.95 to 1.98) | 1.51 (1.08 to 2.11) | Few | N/A | Small | Imprecise | Likely | Very low | |
| Knee injuries | Previous ACL injury ‡ | 1 | Waldén et al 41 | Rel. R | – | 4.5 (2.3 to 8.8) | Very many | N/A | Large | Imprecise | Likely | Very low | |
| Previous ACL injury§ | 1 | Waldén et al 41 | Rel. R | – | 3.4 (1.8 to 6.3) | Very many | N/A | Moderate | Imprecise | Likely | Very low | ||
| Ankle injuries | Age | 1 | Nilstad et al 40 | OR | 0.64 (0.44 to 0.95) | 0.65 (0.4 to 1.05) | Few | N/A | Small | Imprecise | Likely | Very low | |
| Increased 1 RM leg press | 1 | Nilstad et al 40 | OR | 1.47 (1.05 to 2.05) | 1.41 (0.97 to 2.06) | Few | N/A | Small | Imprecise | Likely | Very low | ||
| Foot pronation | 1 | Nilstad et al 40 | OR | 1.56 (1.13 to 2.15) | 1.55 (0.99 to 2.41) | Few | N/A | Small | Imprecise | Likely | Very low | ||
| Reduced knee valgus angle | 1 | Nilstad et al 40 | OR | 1.14 (0.49 to 2.66) | 0.64 (0.41 to 1) | Few | N/A | Moderate | Imprecise | Likely | Very low | ||
| Lower leg/foot injuries | Previous knee injury | 1 | Nilstad et al 40 | OR | 3.73 (1.47 to 9.46) | 3.57 (1.27 to 9.99) | Few | N/A | Large | Imprecise | Likely | Low | |
| Increased BMI | 1 | Nilstad et al 40 | OR | 1.44 (0.84 to 2.49) | 1.4 (0.90 to 2.17) | Few | N/A | Small | Imprecise | Likely | Very low | ||
| Increased age | 1 | Nilstad et al 40 | OR | 1.48 (1 to 2.21) | 1.47 (0.98 to 2.2) | Few | N/A | Small | Imprecise | Likely | Very low | ||
| Groin injuries | Previous groin injury | 1 | Hagglund et al 36 | HR | 2.40 (1.2 to 4.6) | – | Very many | N/A | Small | Imprecise | Likely | Very low | |
RR, rate ratio; Rel. R, relative risk; IRR , incidence rate ratio; BMI, body mass index; ACL, anterior cruciate ligament; BW, body weight; N/A, not available; GRADE, Grading of Recommendations Assessment, Development and Evaluation; NCMJ, non-countermovement jump; RM, repetition maximum; UEFA CL, UEFA Champions League match;
Effect size and CIs in bold indicate significant value. Effect sizes and CIs in normal font indicate non-significant result. Effect sizes classed as small if measures between 0.66–1 and 1 – 2.4, moderate 0.33–0.66 and 2.5 – 4.4, large 0–0.33 and ≥4.5.
*Arnason et al 30 investigated male subjects, whereas Faude et al 33 investigated female subjects—see figure 4 for details.
† Faude et al 33 have investigated female participants only.
‡Denotes where knee used as unit of analysis,
§ Denotes where player used as unit of analysis.