Univariate analysis of risk factors for non-contact anterior cruciate ligament (ACL) injuries
| Risk factor | Matches played | Non-contact ACL injuries | Non-contact ACL rate per 1000 team games | Relative risk | 95% CI |
|---|---|---|---|---|---|
| Location | |||||
| Victorian | 2622 | 50 | 9.5 | Ref | |
| Northern | 1013 | 38 | 18.8 | 1.97 | 1.28 to 3.02 |
| Grade | |||||
| First grade | 2581 | 78 | 15.1 | Ref | |
| Reserve grade | 1054 | 10 | 4.7 | 0.31 | 0.16 to 0.61 |
| Cricket wicket area | |||||
| Yes | 1538 | 37 | 12.0 | Ref | |
| No | 2097 | 51 | 12.2 | 1.01 | 0.66 to 1.55 |
| Enclosed roof | |||||
| Yes | 252 | 6 | 11.9 | Ref | |
| No | 3383 | 82 | 12.1 | 1.02 | 0.44 to 2.36 |
| Time of game | |||||
| Night | 978 | 29 | 14.8 | Ref | |
| Day | 2657 | 59 | 11.1 | 0.75 | 0.48 to 1.18 |
| Previous month’s evaporation | |||||
| High (>48 mm) | 1891 | 63 | 16.7 | Ref | |
| Low | 1530 | 19 | 6.2 | 0.37 | 0.22 to 0.63 |
| Unknown | 214 | 6 | |||
| Previous year’s rainfall | |||||
| High (>600 mm) | 2010 | 40 | 10.0 | Ref | |
| Low | 1410 | 42 | 14.9 | 1.50 | 0.97 to 2.32 |
| Unknown | 215 | 6 | |||
| Ground hardness | |||||
| Firm | 263 | 7 | 13.3 | Ref | |
| Medium | 355 | 9 | 12.7 | 0.95 | 0.35 to 2.59 |
| Soft | 335 | 8 | 11.9 | 0.90 | 0.32 to 2.51 |
| Unknown | 2682 | 64 | |||
| Rain during match | |||||
| None (dry ground) | 1144 | 34 | 14.9 | Ref | |
| None (wet ground) | 65 | 3 | 23.1 | 1.55 | 0.46 to 5.19 |
| Heavy rain | 36 | 1 | 13.9 | 0.93 | 0.12 to 7.02 |
| Light rain | 98 | 2 | 10.2 | 0.69 | 0.16 to 2.90 |
| Unknown | 2292 | 48 | |||
| Primary grass type | |||||
| Bermuda | 758 | 34 | 22.4 | Ref | |
| Kikuyu | 23 | 1 | 21.7 | 0.97 | 0.13 to 7.39 |
| Rye | 1725 | 34 | 9.9 | 0.44 | 0.27 to 0.71 |
| Rye/annual blue grass mix | 700 | 15 | 10.7 | 0.48 | 0.26 to 0.88 |
| Unknown | 429 | 4 | 4.7 | ||
| Stage of season | |||||
| Early (Feb–Apr) | 996 | 40 | 20.1 | Ref | |
| Late (May–Sept) | 2639 | 48 | 9.1 | 0.45 | 0.30 to 0.69 |