This article will discuss some of the key differences between an ankle sprain and an ankle fracture, the latter of which is more commonly referred to as a broken ankle. We will also provide more information about the Ottawa Ankle Rules specifically, which is a useful test that clinicians use to determine if there is enough suspicion of a broken ankle to warrant an X-ray.
What is the difference between a broken ankle vs sprained ankle?
A broken ankle refers to a fracture of one or more of the bones that form the ankle joint, whereas a sprained ankle refers to an injury of one or more ligaments that cross the ankle joint.
What bones are commonly broken in the ankle?
The bones that are typically broken in the ankle are the tibia and fibula, and these breaks usually occur at the distal end, meaning the portions of the bones closest to the ankle joint.
The talus bone can also be broken. This bone lies directly underneath the tibia and fibula, and the connection of these shin bones to the talus forms the talocrural joint.
The calcaneus, or heel bone, is less commonly broken and usually requires a high energy impact in order to become fractured. This bone sits underneath and behind the talus bone. The connection between these bones is referred to as the subtalar joint, which is also part of the ankle joint in general.
What ligaments are commonly sprained in the ankle?
There are many ligaments that cross the ankle joints, and they can be found on the outside, inside, front, and back of the ankle joints. The most commonly injured ligament in the ankle is the anterior talofibular ligament, more simply known as the ATFL. This ligament is found on the outside of the ankle and is usually a main culprit in a rolled ankle, also known as a lateral ankle sprain.
The main ligament that is injured on the inside of the ankle is the deltoid ligament. This is actually a combination of many different individual ligaments, but they fan out and overlay each other, so they can be very difficult to distinguish.
As such, this ligament is often referred to as the deltoid ligament complex. This ligament becomes injured when the inside of the ankle is stretched into a position of excessive eversion, which stretches the inside of the ankle more than the deltoid ligament can handle.
How do you know if you broke or sprained your ankle?
A physiotherapist can often identify if you sprained your ankle through a combination of different clinical tests, and may be able to pin down the exact ligaments involved and extent of injury. Sprains can range from mild, where there is some soreness and swelling, but not major functional impairment, to severe, whereby any sort of movement or weight bearing is very painful.
Technically speaking, it’s possible to break an ankle without sustaining a ligament sprain; however, if you do break an ankle, it’s highly likely that there is also a sprain present. So what does this mean?
If your sprain is severe enough, your doctor or physiotherapist may recommend you seek an x-ray to rule in our out an ankle fracture. An X-ray is one of the most direct and accurate ways to know if you broke your ankle, but there are risks involved with X-rays, mainly the exposure to harmful radiation. Therefore, it’s suggested to seek an X-ray only if it will change the treatment pan for your ankle injury.
How do you know if you need an X-ray for your ankle injury?
One of the first questions patients ask when seeing someone in the clinic for their ankle injury is “Do I need an x-ray?”. This is a very important question for two reasons:
1) It’s imperative we treat the ankle safely and effectively, and as such, it’s important to rule out a broken ankle, which is more formally termed an ankle fracture
2) The effects of radiation are summative over your lifetime. In other words, the more x-rays you get in your life, the more likely you are to experience adverse effects from radiation exposure, so it’s prudent to limit unnecessary exposure to radiation. In the case of an ankle injury, if we confident that an x-ray won’t change the treatment plan, it would make sense to avoid the x-ray.
So how do you know if you need an x-ray? A very common, simple, and validated set of guidelines used to answer this question are the Ottawa Ankle Rules.
Ottawa Ankle Rules (OAR) – General Info
It’s important to know that this set of guidelines is not suitable for everyone. Those who are pregnant, cognitively impaired, or under the age of 18, should be seen by a clinician on an individual basis to assess suitability for an x-ray. Recent research has shown promise in this tool being useful for those aged 6-18 as well; however, the amount of new evidence is limited, so if in doubt it’s a good idea to see a healthcare professional in those cases.
OAR – When to Get an Ankle X-Ray to Assess for an Ankle Fracture
- There is pain in the malleolar zone
AND at least one of the following:
- Bone tenderness along the distal 6cm (2.5 inches) of the posterior edge of the tibia or tip of the medial malleolus
- Bone tenderness along the distal 6cm (2.5 inches) of the posterior edge of the fibula or tip of the lateral malleolus
- Inability to bear weight both immediately AND in the emergency department for 4 steps
OAR – When to Get a Foot X-Ray to Assess for a Foot Fracture
- There is pain in the midfoot region
AND at least one of the following:
- Bone tenderness at the base of the 5th metatarsal
- Bone tenderness at the navicular bone
- Inability to bear weight both immediately AND in the emergency department for 4 steps
Relevant Ankle and Foot Anatomy
In order to properly apply these rules to gain a suspicion of an ankle sprain vs a broken ankle, you will first need to know where to find the different parts of your ankle and foot listed in the Ottawa Ankle Rules. Please refer to the images below for a visual description of where to find these landmarks.
LEFT: Medial aspect of the left foot/ankle
RIGHT: Lateral aspect of the left foot/ankle
How good are the Ottawa Ankle Rules at diagnosing a sprained ankle vs broken ankle?
It’s important to clarify that these rules are not meant to specifically diagnose your ankle injury. Rather, they are simply used to help rule out a fracture and subsequent need for an x-ray.
Even if you can confidently rule out a fracture, it’s still highly recommended to get your ankle checked out by a doctor or physiotherapist for further evaluation and treatment, and to ensure that noting was missed when applying the Ottawa Ankle Rules.
With all that in mind, studies have researched the effectiveness of this tool, and it’s been proven to be quite accurate for ruling out ankle and midfoot fractures. For example, a systematic review published by Bachmann et al in the British Medical Journal (BMJ) in 2003, which combines and analyses the results of a multitude of studies and thus offers a high level of evidence, reported the following:
– For people who originally tested negative for an ankle or midfoot fracture on the Ottawa Ankle Rules, just under 2% of them actually had a fracture on x-ray.
– This study revealed a consistently high sensitivity for this tool. This means that if you test negative, or don’t have any of the findings listed in the testing criteria above, that it is very unlikely you have a fracture on x-ray. However, the specificity was considered good, but not excellent. That means that if you test positive and are sent for an x-ray, there’s a chance the x-ray may show that you don’t have a fracture. In other words, being negative on the Ottawa Ankle Rules carries a bit more weight or confidence, whereas being positive is an indication that the injury is severe enough to warrant an x-ray even though it may not always reveal a fracture.
– One of the proposed reasons that the specificity is low, and therefore you can’t determine if there is a fracture based on this tool alone, relates to variability in testing and clinical expertise. Additionally, the time from injury at which one is tested could influence results as well. If you think of an instance where someone rolls their ankle, any sort of palpation may be quite sensitive the first day, but may settle quickly over time, leading to different findings on Day 1 vs Day 3. This is why some people may be sent for an x-ray based on the physical exam, only to find they don’t actually have a fracture.
– These findings have been verified numerous times since the publication of the Bachmann article in 2003. For example, most recently in 2022, another systematic review conducted by Gomes et al was published in BMC Musculoskeletal Disorders and verified the general findings of previous studies, agreeing that the value of this tool relates to it’s high sensitivity, but the specificity lends itself to some false positives (i.e. being sent for an x-ray and having the x-ray show no fracture).
Therefore, to summarize, the Ottawa Ankle Rules are very helpful to rule out the need for an ankle or midfoot x-ray. While you may be able to get a general sense of your condition by applying this test on yourself, it’s highly recommended to have an experienced clinician, such as a doctor or physiotherapist, perform the examination as well for a higher level of confidence in the findings.
Still Unsure? Things to Consider:
The Ottawa Ankle Rules are typically applied by clinicians like doctors and physiotherapists, as they have the knowledge and clinical expertise to confidently landmark and palpate the appropriate anatomy.
If in doubt, please do not hesitate to consult with your doctor or physiotherapist regarding suitability for an x-ray. If you do not have a family doctor or cannot visit a physiotherapist, any walk-in clinic should be appropriate to help make an informed decision.
While accurate, valid, and reliable, these guidelines aren’t perfect. For example, if you having trouble weight bearing and walking, but don’t fit the other criteria for an x-ray, and your symptoms don’t improve after about a week, then I would consult with a doctor or physiotherapist to see if they feel an x-ray is worth it at that point.
In general, if you don’t feel confident testing these guidelines on yourself, are confused about the anatomy, or just find you can’t get to a clear answer, please visit a healthcare professional for more information.
References
Bachmann LM, Kolb E, Koller MT, Steurer J, ter Riet G. Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. BMJ. 2003 Feb 22;326(7386):417. doi: 10.1136/bmj.326.7386.417. PMID: 12595378; PMCID: PMC149439.
Gomes, Y.E., Chau, M., Banwell, H.A. et al. Diagnostic accuracy of the Ottawa ankle rule to exclude fractures in acute ankle injuries in adults: a systematic review and meta-analysis. BMC Musculoskelet Disord 23, 885 (2022). https://doi.org/10.1186/s12891-022-05831-7
https://physio-pedia.com/Ottawa_Ankle_Rules
Disclaimer:
The content here is designed for information & education purposes only and is not intended for medical advice.
