The Ottawa knee rule: avoiding unnecessary radiographs in sports.

Physicians are often called upon to evaluate acute knee injuries. Radiographs are frequently ordered, but they may not be helpful for making the diagnosis and guiding treatment of soft-tissue injuries. A set of clinical criteria, called the Ottawa knee rule, has been established to predict when radiographs are truly necessary. The sensitivity and negative predictive value of the rule were both validated at 100% for fractures of the knee in adults. By using the Ottawa knee rule, at least 25% of unnecessary films can be avoided without risking patient safety. The rule has not specifically been studied among sports participants, but indications are that it can be useful in this population.