We previously wrote an article describing the differences between a broken ankle vs. sprained ankle, and in that article we touched on the discussion of whether or not to get an x-ray for an ankle injury.
In this article, we will get straight to the point, hopefully allowing a little more clarity when it comes to answering this important question and differentiating between two of the most common ankle injuries.
What can an x-ray see?
X-rays are very useful in visualizing the bones in the ankle and foot to detect or rule out a fracture, as well as the spacing between the bones, the latter of which provides an idea of joint space narrowing.
Therefore, x-rays can help assess the extent of bony ankle injuries, and sometimes help assess injuries to the ankle joint (e.g. high ankle sprains).
What an x-ray does NOT do is visualize the soft tissue around the ankle, which includes the ankle ligaments, muscles, tendons, fascia, joint cartilage, fat tissue, and skin.
For example, an x-ray won’t be able to assess the integrity of ligaments damaged during an ankle sprain, and it will not be able to pick up on muscle or tendon strains in most cases.
The occasional exception would be to do with avulsion fractures, whereby the tendon or ligament tears from the bone and brings a piece of bone with it.
Why not get an x-ray for every injury?
The reason you should be asking if you need an x-ray for a sprained ankle, as opposed to just going to get one without thinking about it, is because x-rays involve ionizing radiation. This radiation is harmful to your body, particularly your DNA, and the effects add up over time, so it doesn’t just wear off eventually.
X-ray technology is constantly improving to provide better images with a smaller dose of radiation, but at the end of the day, it’s still a very important consideration, especially when an ankle sprain can usually be treated very well with conservative measures.
Should you get an x-ray for a sprained ankle?
An x-ray is indicated for a sprained ankle if there is a need to identify or rule out a fracture.
Therefore, as physical therapist who often sees patients very shortly after their acute ankle injuries, I will often ask myself “Will an x-ray have a potentially important impact on the patients treatment plan?”
If the results of an x-ray won’t affect the patient’s treatment plan, then we generally don’t perform an x-ray. If it is thought that the results of an x-ray will provide crucial information in guiding the treatment plan, an x-ray will likely be ordered at that time.
So how do we know if an x-ray could change the treatment plan for someone who present with a sprained ankle?
Ottawa Ankle Rules
The Ottawa Ankle Rules are a set of valid and reliable diagnostic criteria to help determine if it’s worth the risk of receiving ionizing radiation from an x-ray to detect or rule out an ankle fracture (Bachmann et al, 2003). We will list the associated criteria for getting an ankle or foot x-ray in the section below.
In addition, if someone has a history of severe osteoporosis or other bone diseases, or if there was a high energy impact involved, like a fall from a height or a car accident, then we will typically lean towards an x-ray if there is any doubt.
Here is an image that will help in understanding the criteria involved in the Ottawa Ankle Rules:
Ottawa Ankle Rules – Criteria for an Ankle X-Ray
- 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
Ottawa Ankle Rules – Criteria for a Foot X-Ray
- 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
Real-Life Example of a Patient Who Received an X-Ray for a Sprained Ankle
A couple months ago I assessed a young gentleman who sprained his ankle playing tennis. In this case, the patient jumped up in the air and landed with an inverted ankle, thus rolling the ankle on landing, which is a very common way to sustain ankle injuries.
He experienced sudden ankle pain, but especially the outside of the ankle joint, and significant swelling and bruising happened almost immediately. He was able to put some weight on it, but not very much, and not for very long.
The patient presented to the clinic a few days after his injury and reported no change in his symptoms and had not yet received a physical therapy consult.
The patient’s ankle was still very swollen and bruised, and he was having trouble walking, although it should be noted he was able to tolerate some weight bearing (walking for short distances with one crutch).
In terms of the Ottawa Ankle Rules, he was certainly tender in the zones described above, with maximum pain on the tip of the lateral malleolus and surrounding ligaments. His swelling was so significant that he was forming small blood blisters over the injured area, which is a little more rare with a simple ankle sprain.
However, the one criteria of the Ottawa Ankle Rules that he did not meet was inability to weight bear after the injury. While he was able to walk on it, he expressed significant pain and reduced ability to fully weight bear more than a few steps.
This made it a bit of a grey area. His symptoms were mostly severe, but he was also able to put some weight on the ankle. Given this patient’s history as a high level athlete and military veteran, there was concern that he was simply “gutting it out”, and that there may be an underlying ankle fracture, which would alter our strategy for treatment.
In this case, we decided to get request an x-ray, which he had that day. The x-ray was negative for any fracture, so we were able to proceed by treating this as a severe ankle sprain, as opposed to an ankle fracture. This represents one of the more liberal situations where we would need an x-ray for a sprained ankle.
If this patient had a higher energy impact, or inability to weight bear after the injury on top of his current symptoms, then it would be a no-brainer to get an x-ray and spend some time protecting the ankle in a walking boot until more information is gathered.
If this patient had less severe swelling, bruising, and tenderness over the bones, or if his symptoms were improving more rapidly (especially ability to bear weight), then we would have been more comfortable saying he doesn’t need an x-ray and treating as an ankle sprain.
Summary
It’s not always cut and dry when you should get an x-ray for a sprained ankle; however, the Ottawa Ankle Rules provides an excellent tool to assess the need for an ankle x-ray, with good reliability and validity.
It s highly recommended to consult with a doctor or physical therapist if you suspect you have sprained or broken your ankle. They can administer various tests with confidence, and can get you started on managing your ankle injury even if needing to wait for an x-ray.
References
Bachmann, L. M., Kolb, E., Koller, M. T., Steurer, J., & ter Riet, G. (2003). Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. Bmj, 326(7386), 417.
Disclaimer:
The content here is designed for information & education purposes only and is not intended for medical advice.
