Orthopedic Decision-Making Made Easy for the Ankle and Knee | ThriveAP

A while ago, I discussed the concept of clinical prediction rules. Essentially, these rules are tools nurse practitioners can use to simplify and increase the accuracy of clinical decision making. If you’ve ever used Wells Criteria to rule out a DVT for example, you’ve used a clinical prediction rule. I frequently take advantage of such algorithms in my own nurse practitioner practice as they lend an added level of confidence to my course of diagnosis and treatment. So, today, let’s talk about a few of these guidelines as they relate to orthopedics.

My first nurse practitioner position was at a walk-in clinic. When the X-ray tech on staff was absent, or the machine experiencing difficulties, I would order X-rays for my patients the old school way, writing the order on a prescription pad and sending the individual to an outlying medical imaging office. Such an inconvenience. Not only did the patient potentially have a broken ankle or wrist, they then had to hobble back to their car, drive to get an X-ray at another facility, then commute back to the clinic. So, I was motivated to avoid ordering X-rays on a whim. Fortunately, there are a few orthopedic clinical prediction tools that came to my rescue. 

Ottawa Ankle Rules

The Ottawa Ankle Rules help medical providers determine if radiography is necessary in the case of an injury to the mid-foot or ankle. The decision-making algorithm has a sensitivity of 90-100% meaning when the criteria are negative, there is a 90-100% probability that the patient does not have an ankle or mid-foot fracture. So, an X-ray is not necessary. Ottawa Ankle Rules can reduce the rate of unnecessary ankle and foot X-rays by an estimated 25-30%.

An ankle X-ray series is required only if there is pain in the malleolar zone and any of these findings…

1. Bone tenderness is present at the posterior edge or tip of the lateral malleolus (#1)

OR

2. Bone tenderness is present at the posterior edge or tip of the medial malleolus (#3)

OR

3. Inability to bear weight both immediately after the injury and in the emergency department or clinic. Bearing weight counts even if the patient limps.

A foot X-ray series is required only if there is pain in the mid-foot zone and any of these findings…

1. Bone tenderness is present at the base of the 5th metatarsal (#2)

OR

2. Bone tenderness is present to the navicular bone (#4)

OR

3. Inability to bear weight for 4 steps both immediately after the injury and in the emergency department or clinic. Bearing weight counts even if the patient limps.

Caveats…

Although the Ottawa Ankle Rules are quite accurate for predicting which patients do not have a an ankle of mid-foot fracture, sound clinical judgment remains imperative in treating patients with injuries to the ankle and foot. These rules should only be used in patients aged 2 and older. Intoxicated and uncooperative patients may not provide enough information to the examiner for the rules to be effective. Significant swelling may prevent adequate examination in regards to bony tenderness. Always provide patients with written instructions outlining follow up and return precautions.

Ottawa Knee Rule

Similarly to the Ottawa Ankle Rules, the Ottawa Knee Rule is a highly effective method for determining which patients with knee injuries require radiography. The Ottawa Knee Rule is 98-100% sensitive meaning when the criteria are negative, there is a 98-100% probability that the patient does not have a knee fracture. An X-ray is not necessary. The Ottawa Knee Rule may reduce the rate of unnecessary knee X-rays by 20-30%, a cost savings for patients.

A knee X-ray series is required only for knee injury patients with any of these findings…

1. Age 55 or older

OR

2. Isolated tenderness of the patella (#1)

OR

3. Tenderness of the head of the fibula (#2)

OR

4. Inability to flex to 90 degrees

OR

5. Inability to bear weight

Caveats…

Although the Ottawa Knee Rule is quite accurate for predicting which patients do not have a knee fracture, good judgment is essential in treating patients with injuries to the knee. These rules should only be used in patients aged 2 and older. Some studies even suggest the rules should only be used on patients aged 18 and older. Intoxicated and uncooperative patients may not provide enough information to the examiner for the rules to be effective. Diminished sensation to the leg(s) is a red flag and warrants further evaluation. Always provide patients with written instructions outlining follow up and return precautions.

Which orthopedic clinical prediction rules do you use as a nurse practitioner?

You Might Also Like: Mix & Match: Upper Extremity Splints and Fractures