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Injury Update - Australia's best information source for elite sports injuries

The relationship between ground conditions and injury in football

Football matches (including American football, soccer, rugby union, rugby league and Australian football) traditionally take place on natural grass, although artificial turf is a common substitute in American football. Previous comparison studies of safety between Astroturf and natural grass have shown conflicting results, although in general the range of outcomes has been of either equivalent risk or that natural grass is safer. Knee Anterior Cruciate Ligament (ACL) injury risk has been shown to be lower in situations where shoe-surface traction is reduced. In open Astroturf stadiums in the NFL, for example, shoe-surface traction is reduced as the temperature drops, which correlates with a decrease in ACL injury risk. It has been claimed that new generation artificial turf surfaces are safer than Astroturf, primarily because of reduced hardness. Two comparison studies have been published with respect to new generation artificial surfaces and natural grass, using bermudagrass and, probably, Kentucky bluegrass, as the comparison groups. In both of these studies there has been no increase in injuries on the new generation artificial surfaces.

In Australian football, with respect to ACL injuries, there are long-standing statistically-significant biases towards more injuries in the early months of the season and on grounds that are further to the north of Australia (in warmer climates). The early-season bias for ACL injuries also exists for natural grass surfaces in the NFL competition. There is an early-season ACL bias for the NFL on Astroturf surfaces in open air conditions but not on Astroturf surfaces in closed arenas. There is also no ‘southern’ or warm-climate bias demonstrated in the NFL. Further analysis of Australian football reveals that the risk of ACL injury is significantly lower on grounds that have perennial ryegrass as the major species, compared to bermudagrass. This explains both the warm-climate and early-season biases. There is only a minimal correlation between hardness, as measured on natural grass fields by the penetrometer, and ACL injury risk in Australian football. Perennial ryegrass, compared to other common turfgrass species such as bermudagrass, Kentucky bluegrass and annual bluegrass, generally leads to surface conditions with reduced shoe-surface traction. This is because perennial ryegrass produces less thatch and has fewer rhizomes (or stolons) which may create excess friction between the shoe cleats and grass layer. The use of perennial ryegrass is the best explanation for the lower ACL injury rates in the southern parts of Australia. The early-season bias exhibited in all examined competitions played on natural grass is likely to be related partly to the increased predominance of ryegrass in the latter stages of the season and partly to the decrease in thatch and lateral growth due to traffic during the season.

Natural turfgrass surfaces incorporating good thatch and lateral growth control are almost certainly the ‘safest’ surfaces on which to play football of all codes. However, when natural grass is not controlled it may be less safe than new generation artificial surfaces. Ryegrass is the species that naturally tend to minimise shoe-surface traction and therefore leads to the safest playing surface. Whilst ryegrass is not suitable as a single species in very warm or cool climates, it can usually be incorporated as part of the profile. When other hardier species (with respect to the particular climate) are used, careful control of thatch and lateral growth can be undertaken to minimise the chance of creating excessive shoe-surface traction.

Useful references:

Rainfall, evaporation and the risk of non-contact anterior cruciate ligament injury in the Australian Football League, Orchard J, Seward H, McGivern J, Hood S, Medical Journal of Australia 1999, 165: 304-306. Click to read

The Northern Bias for Injuries in the Australian Football League, Orchard J, Australian Turfgrass Management, June 2000, 23: 36-42. Click to read

Intrinsic and Extrinsic Risk Factors for Anterior Cruciate Ligament injury in Australian Football, Orchard J, Seward H, McGivern J, Hood S, American Journal of Sports Medicine 2001, 29 (2): 196-200. Click to read

The AFL Penetrometer study: work in progress, Orchard J, Journal of Science and Medicine in Sport 2001, 4(2): 220-232. Click to read

Risk of knee and ankle sprains under various weather conditions in American football, Orchard J, Powell J, Medicine & Science in Sports & Exercise, 2003 Jul; 35(7):1118-23. Click to read

Is there a relationship between ground and climatic conditions and injuries in football?, Orchard J, Sports Medicine 2002, 32 (7): 419-432. Click to read

Ryegrass is associated with fewer non-contact anterior cruciate ligament injuries than Bermudagrass, Orchard J, Chivers I, Aldous D, Bennell K, Seward H, British Journal of Sports Medicine, 2005, 39: 704-709. Click to read

Influence of environmental and ground conditions on injury risk in rugby league, Gabbett T, Minbashian A, Finch C, Journal of Science and Medicine in Sport, 2007 (in press) Click to read

The relationship of Australian Football grass surfaces to anterior cruciate ligament injury, Chivers IH, Aldous DE, Orchard JW. International Turfgrass Society Research Journal, 2005, 10: 327-332. Click for further info

Risk of injury in elite football played on artificial turf versus natural grass: a prospective two-cohort study, Ekstrand J, Timpka Tand Hägglund M. British Journal of Sports Medicine 2006;40:975-980. Click to read

Incidence, Causes, and Severity of High School Football Injuries on FieldTurf Versus Natural Grass: A 5-Year Prospective Study. Meyers MC and Barnhill BS. American Journal. of Sports Medicine, Oct 2004; 32: 1626 - 1638. Click to read abstract

Read about a major ground and safety initiative from the University of Ballarat