Objectives: The majority of football injuries are caused by trauma to the lower extremities. Shinguards are considered an important measure in preventing lower leg impact abrasions, contusions and fractures. Given these benefits, Federation Internationale de Football Association introduced the shinguard law in 1990, which made wearing shinguards during matches mandatory. This study evaluated the effect of the introduction of the shinguard law for amateur players in the Netherlands in the 1999/2000-football season on the incidence of lower leg injuries. Design: Time trend analyses on injury data covering 25 years of continuous registration (1986-2010). Methods: Data were retrieved from a system that records, all emergency department treatments in a random, representative sample of Dutch hospitals. All injuries sustained in football by patients aged 6-65 years were included, except for injuries of the Achilles tendon and Weber fractures. Time trends were analysed with multiple regression analyses; a model was fitted consisting of multiple straight lines, each representing a 5-year period. Results: Patients were predominantly males (92%) and treated for fractures (48%) or abrasions/contusions (52%) to the lower leg. The incidence of lower leg football injuries decreased significantly following the introduction of the shinguard law (1996-2000: -20%; 2001-2005: -25%), whereas the incidence of all other football injuries did not. This effect was more prominent at weekends/match days. No gender differences were found. Conclusions: The results significantly show a preventive effect of the shinguard law underlining the relevance of rule changes as a preventive measure and wearing shinguards during both matches and training sessions. (C) 2014 Sports Medicine Australia, Published by Elsevier Ltd. All rights reserved.