The Ottawa Ankle Rules (OAR), developed in 1992, are a set of clinical guidelines designed to help healthcare providers determine when an X-ray is needed to rule out fractures in the ankle and mid-foot. These rules were developed to minimize unnecessary X-rays while maintaining a high sensitivity for detecting fractures. The goal is to identify those who need imaging and avoid exposing patients to unnecessary radiation.
Background and Purpose
Despite the high frequency of ankle sprains in sports, only a small percentage of these injuries (less than 15%) result in fractures. This low incidence led to the development of the Ottawa ankle rules, which assess specific signs, including the ability to walk and the presence of tenderness in key areas of the foot and ankle. These rules were designed to quickly rule out fractures, allowing for more efficient triage in emergency departments.
How the Ottawa Ankle Rules Work
To assess the ankle, the rules check if the patient can walk four steps without difficulty and examine for tenderness over specific spots: the anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament. For the mid-foot, the rules assess walking ability and tenderness over the navicular bone or base of the fifth metatarsal. These tests focus on sensitivity, aiming to ensure that as few fractures as possible are missed.
Effectiveness of the Ottawa Ankle Rules
The Ottawa ankle rules are very sensitive, meaning they can reliably catch most fractures (with a nearly 100% sensitivity in many studies). However, their specificity varies significantly, ranging from 10% to 79%. This variability is influenced by factors like the experience of healthcare providers and patient variability in expressing pain. Despite the lower specificity, the rules’ high sensitivity helps reduce the number of unnecessary X-rays. Studies show that fewer than 2% of patients who test negative for fractures actually have one, indicating the rules’ reliability.
Impact on Clinical Practice
A study of 2,342 patients in emergency departments found that implementing the Ottawa ankle rules reduced ankle radiography by 28% and foot radiography by 14% at intervention hospitals. In addition to reducing X-ray use, there were reductions in patient waiting times and medical costs, with no significant difference in patient satisfaction or subsequent radiographs. The rules showed high sensitivity for detecting fractures, with a sensitivity of 1.0 (100%) for malleolar fractures and 1.0 for midfoot fractures.
Research Spotlight
A 2025 study from the Bulletin of Emergency and Trauma compared the well-known Ottawa Ankle Rules (OAR) with a newer method called the Shetty Test (ST) for identifying ankle and foot fractures. Among 112 adult patients with ankle injuries, the OAR showed higher sensitivity (94.7%) but lower specificity (15%) compared to the ST (68.4% and 76.3%, respectively).
When both tests were used together, sensitivity and the ability to rule out fractures (negative predictive value) reached 100%.
The authors concluded that while the Shetty Test did not outperform the Ottawa Ankle Rules, it is a simple and reproducible addition—especially helpful for non-orthopedic providers—and combining both tests may improve fracture screening accuracy. (“Study comparing the Ottawa Ankle Rules and Shetty Test for ankle fractures – see PubMed.”)
Summary and Key Takeaways
The Ottawa ankle rules are a valuable tool for ruling out fractures in the ankle and mid-foot. Their high sensitivity significantly reduces unnecessary X-rays, which helps reduce patient costs and waiting times. The variability in specificity highlights the importance of provider experience, but overall, the rules have a substantial impact on clinical practice by decreasing unnecessary imaging and improving patient flow in emergency departments.
References / Citations (Optional)
Stiell I G, McKnight R D, Greenberg G H, McDowell I, Nair R C, Wells G A, Johns C, Worthington J R. “Implementation of the Ottawa Ankle Rules.” Orthobullets.
