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Toolbox - Ottawa knee and ankle rules

Our new series opens with GP and sport and exercise medicine registrar Dr James Thing’s quick-fire advice on how and when to use this tool in primary care

 

The Tool

The Ottawa knee and ankle rules are a validated set of assessment tools to help the clinician decide whether an X-ray is needed after an acute injury to the knee or the foot and ankle.  The rules are designed to aid the early identification of a fracture while reducing unnecessary radiography in patients who have negative clinical findings.

When to use it

The Ottawa knee and ankle rules can be used for any blunt traumatic injury to the knee or foot and ankle where a potential fracture needs to be excluded.  They are often used to determine whether a patient needs to be reviewed in A&E.

A typical scenario where the Ottawa ankle rule may be used is when a patient complains of having ‘sprained’ their ankle.  The foot and ankle are often swollen and tender and the initial management requires the clinician to exclude a fracture of the ankle or mid-foot.1

The Ottawa ankle rule says that an ankle X-ray is required if the patient presents with pain in the malleolar zone (see diagram below) and any of the following findings:

  1. inability to weight bear (for four steps) at the time of injury or at time of presentation
  2. bony tenderness at the posterior edge of the distal 6cm of the medial (tibia) or lateral malleolus (fibula) (see diagram below).

A foot X-ray is required if the patient presents with pain in the mid-foot zone and any of the following findings:  

  1. inability to weight bear (for four steps) at the time of injury or at time of presentation
  2. bony tenderness over the navicular or the base of the fifth metatarsal (see diagram below).

The Ottawa knee rule can be used for any blunt traumatic injury to the knee when a fracture of the distal femur, patellar, proximal tibia or fibula needs to be excluded, for example after a fall onto the knee with pain and swelling.

Ottawa ankle rules

Ottawa ankle rules diagram - SUO

The Ottawa knee rule says that a knee X-ray is required if the patient presents after trauma with at least one of the following findings:

1) age over 55 years or younger than 18 years

2) bony tenderness at the fibular head or over the patella

3) inability to flex the knee to 90°

4) inability to weight bear (for four steps) at the time of injury or at time of presentation.

Both the Ottawa ankle rules and the Ottawa knee rules apply only for individuals who are over 18 years of age. You should also be cautious in using the rules in patients who are intoxicated, who have other painful ‘distracting’ injuries, who have reduced lower-limb sensation or gross swelling that prevents palpation.2,3

The evidence

Ottawa ankle rule

Blunt traumatic ankle injury is extremely common, and most individuals – 85% - don’t sustain a fracture.1  The Ottawa ankle rule has a high sensitivity (98.2 - 100%) and so will pick up almost all fractures, but the specificity is low (42.3 – 77.1%).1 The tool is not designed to diagnose a fracture but simply to ensure that none are missed.  The results from a meta-analysis in the BMJ in 2003 demonstrate that less than 2% of fractures were missed when the Ottawa ankle rule was used.1

Ottawa knee rule

Only around 6% of acute knee injuries result in a fracture. The Ottawa knee rule has a high sensitivity (94 - 100%), and correctly identified all 63 knee fractures in a series of 1251 patients.3  In this cohort the tool enabled 511 patients to avoid having an X-ray.  In another study the Ottawa knee rules prevented unnecessary X-rays in 49% of 2315 patients with an acute knee injury.4

Click here for an at-a-glance summary of the rules which you can print out and keep.

 

Dr James Thing is a GP in and a sport and exercise medicine registrar at the Royal London Hospital.  Dr Thing is also a member of the Faculty of Sport and Exercise Medicine.

The Faculty of Sport and Exercise Medicine works to develop and promote the medical specialty of Sport and Exercise Medicine. The specialty is made up of three elements; exercise as a way to improve health, exercise as treatment for illness, and the treatment of injuries from sport. Click the link to find out more.

 

References

1 Bachmann LM, Kolb E, Koller MT et al.  Accuracy of Ottawa ankle rules to exclude fractures of the ankle and mid-foot: systematic review. BMJ, 2003; 326:417

2 Stiell IG, McKnight RD, Greenberg GH et al. Implementation of the Ottawa ankle rules.JAMA, 1994;271(11):827-32

3 Stiell IG, Greenberg GH, Wells GA et al. Prospective validation of a decision rule for the use of radiography in acute knee injuries. JAMA, 1996;275(8):611-5

4 Emparanza JI, Aginaga JR; Estudio Multicéntro en Urgencias de Osakidetza: Reglas de Ottawa (EMUORO) Group. Validation of the Ottawa Knee Rules. Ann Emerg Med, 2001;38(4):364-8

 

 

 

 

 

 

 

 

 

 

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