When Is It Appropriate To Get An X-Ray After An Acute Ankle Or Knee Injury?

I recently sustained a severe inversion ankle sprain. When the pain was at its worst, I was concerned about a possible distal fibular fracture. For a very brief moment, I considered the possibility of an X-ray to rule in or rule out a fracture. However, through my own clinical reasoning I determined that the X-ray was unnecessary. Thankfully, I knew exactly what to do in this situation and started my own rehabilitation right away. Two weeks after the ankle sprain and non stop rehab, I am back to my regular training regimen without difficulty. Of course swelling and soreness is still a factor, but that is to be expected as the soft tissue structures are still undergoing the healing process.

I am extremely thankful that I had the education and capabilities to start my own rehab just minutes after the ankle sprain. I am also very thankful I had the knowledge to know that I did not have to waste time and money on an unnecessary X-ray. However, this left me pondering what a person who is not medically trained would do in this situation. With the amount of pain I was in, the significant amount of swelling and bruising, and decreased function and range of motion, I know this situation would be extremely concerning for anyone. I wouldn’t blame someone with that severity of injury and no medical background for wanting an X-ray. 

Nevertheless, this got me thinking that the general public should have the basic knowledge on how to avoid unnecessary imaging after an acute ankle or knee injury. Luckily, a lot of research has been done to develop screening tools for acute ankle and knee injuries. 

Acute Ankle Injuries

It is estimated that approximately 25,000 ankle sprains occur per day in the USA, meaning they are extremely common.1 Still, less than 15% of those ankle sprains resulted in a clinically significant fractures.2 To help lower healthcare costs, the Ottawa Ankle Rules were developed to help determine which of these patients need radiographs following an acute ankle injury, and which patients do not. 

There are 5 components to help decide whether you need imaging of the ankle:3

1. Bony tenderness along distal 6 cm of posterior edge of fibula or tip of lateral malleolus

2. Bony tenderness along distal 6 cm of posterior edge of tibia/tip of medial malleolus

3. Bony tenderness at the base of 5th metatarsal

4. Bony tenderness at the navicular

5. Inability to bear weight both immediately after injury and for 4 steps during initial evaluation

An Ankle X-ray is only required if:3

• There is any pain in the malleolar zone; and,

• Any one of the following:

  • Bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus, OR

  • Bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus, OR

  • An inability to bear weight both immediately and in the emergency department for four steps.

Acute Knee Injuries

It is estimated that 1.3 million people are seen annually in US emergency departments due to acute knee injuries. However only 6% of these people have actually sustained a fracture, with more than 92% of radiographic results being negative for fractures.4 To help lower healthcare costs, the Ottawa Knee Rules were developed to help determine which of these patients need radiographs following an acute knee injury, and which patients do not. 

If ONE of the following is present, an X-ray is indicated:5

1. Age >55 years

2. Isolated patellar tenderness without other bone tenderness

3. Tenderness of the fibular head

4. Inability to flex the knee to 90°

5. Inability to bear weight immediately after injury and in the emergency department (4 steps) regardless of limping

Even with this knowledge, it can still be a daunting task to decide whether or not you need imaging. Still unsure if you can decide for yourself if you need imaging or not? At The PATH, we are more than capable to help guide you through this process, and to help determine whether your injury is appropriate for imaging or not. Schedule a FREE Phone Consultation with us today to get started! 

1. Doherty, C., Delahunt, E., Caulfield, B., Hertel, J., Ryan, J. and Bleakley, C., 2014. The incidence and prevalence of ankle sprain injury: a systematic review and meta-analysis of prospective epidemiological studies. Sports medicine, 44(1), pp.123-140. 

2. Brooks SC, Potter BT, Rainey JB. Inversion injuries of the ankle: clinical assessment and radiographic review. BMJ 1981; 282: 607-608

3. Stiell IG, McKnight RD, Greenberg GH, McDowell I, Nair RC, Wells GA, Johns C, Worthington JR. Implementation of the Ottawa Ankle Rules. JAMA 1994;271:827-32.

4. National Center for Health Statistics. National Hospital Ambulatory Medical Care Survey 1992. Hyattsville, MD:National Center for Health Statistics; 1994.

5. Stiell IG, McKnight RD, Greenberg GH, McDowell I, Nair RC, Wells GA, Johns C, Worthington JR. Implementation of the Ottawa Ankle Rules. Journal of the American Medical Association 1994; 271:827-832.

Dr. Samantha Benavides

PT, DPT

Co-Owner

The PATH Rehab & Performance