Tuesday, March 18, 2008

Cutting-Edge Research: Studs, Blades and Knee Injury

When selecting a new pair of boots, today’s player has wide range of choices. From soft ground to firm ground, from leather to synthetic, the selection is impressive. Players often debate the advantages of various styles and brands of boot. Weight, material, flexibility and side lacing are all reported to affect performance. Cleat pattern is another factor that is often taken in to consideration when purchasing a new pair of boots. Typically molded cleats are designed as round studs or oval-shaped blades. A quick Google search shows that there is considerable debate among internet publishers and bulletin board patrons over the use of bladed and studded cleats. Some argue that the design of the cleat can lead to knee injuries. Two recent studies have attempted to clear up this controversy examining the effects of studded and bladed cleats on knee stress.


One of the more common types of non-contact knee injury occurs when the foot “sticks” to the ground and the knee experiences abnormal stress. As the player stops suddenly or plants his or her foot to make a cut, the shoe stays firmly planted on the ground and the knee experiences both shear and rotational stress. This, in turn leads to increased risk of knee injury, particularly ruptures of the anterior cruciate ligament. Some argue that bladed cleat pattern causes greater traction than studs and raise the potential for damage to the knee.

This issue was recently addressed in a study published in the American Journal of Sports Medicine. The author, Rajiv Kaila investigated knee loading patterns during various sidestep, cutting maneuvers. In this study, 15 professional players performed the movements while wearing two types of studded boots (Adidas Copa Mundal and Nike Air Zoom Total 90 FG) and two types of bladed boots (Adidas Preditor Pulse FG and Nike Mercurial Vapor FG). Players ran at a target, planted their dominant foot and made a sidestep cut at 30° and 60° to the direction of the run. Knee movements, forces and torques (twisting forces) were measured during each of the maneuvers.

The results showed that there were no differences in the amount of force, stress or the degree of unwanted knee movement wearing any of the four styles of shoe. There were clearly no differences between the two bladed and two studded cleats. The author surmised that the soccer boot type had no effect on knee stress and that neither cleat style elevated the risk of knee injury.

Rajiv Kaila’s study was backed up by a similar report in the International Journal of Sports Medicine. Investigators from Germany had players perform complex turning movements (180°) while wearing studded and bladed boots. They also found that knee stress and unwanted movements were similar between the two types of cleat design. This lead the researchers to conclude that there no higher risk of knee joint injury wearing either style of cleat.

The authors are quick to point out that a key limitation to their studies is that both only examined adult males. Females and younger players were not included in either study. Females and young males have somewhat different knee mechanics when executing sidestep and cutting maneuvers. They also noted that the studies were conducted in rested subjects and that fatigue can alter movement patterns and increase injury risk. Lastly, the study by Kaila was performed on turf (FieldTurf) and response on grass may be different. So there is the possibility that cleat design may be a more important factor in females or during the later part of a match. However, while these limitations are important to consider, it seems reasonable to conclude that the cleat design, studs or blades, does not appreciably increase the risk of knee injury.


So, blades or studs? As far as the risk of knee injury goes, either is fine.

References

Kaili R (2007) Influence of modern studded and bladed soccer boots and sidestep cutting on knee loading during match play conditions. American Journal of Sports Medicine, 35:1528-1536.

Gehring D, Rott F, Stapelfeldt B, Gollhofer A (2007) Effec of soccer shoe sleats on knee joint loads. International Journal of Sports Medicine, 28:1030-1034.