Imagine you're on your orthopaedic rotation, and a patient hobbles in with an acute ankle injury. Your first instinct might be to order an X-ray, right? Hold that thought. That's where the Ottawa Rules come in – they're your evidence-based guide to decide who really needs that initial radiograph.

Think of the Ottawa Rules not as absolute laws, but as highly reliable algorithms to help you filter out the low-risk patients, saving them from unnecessary radiation, cost, and the bottleneck in radiology.

For Ankle and Foot Injuries:

Okay, picture this: someone twisted their ankle a few hours ago. They're in pain around the malleoli – those bony bumps on either side. Now, you need to ask yourself:

1. Is there bony tenderness in specific zones? Get your fingers out and palpate:
   • Along the distal 6 cm of the posterior edge of the tibia (that's the back of the shin bone) or the tip of the medial malleolus (the inner bump).
   • Along the distal 6 cm of the posterior edge of the fibula (the outer lower leg bone) or the tip of the lateral malleolus (the outer bump). If they wince with tenderness in either of these areas, that's a point towards needing an X-ray.
2. Can they bear weight? This is crucial. Ask them:
   • Could they take at least four steps immediately after the injury?
   • Can they take at least four steps now, in the clinic or ED? If the answer to either of these is "no," that's another indication for imaging.

Now, the foot has its own criteria if the pain is primarily in the midfoot:

1. Bony tenderness again:
   • At the base of the fifth metatarsal – that prominent bone on the outside of the midfoot.
   • At the navicular bone – that little bump on the inside arch of the foot.
2. Weight-bearing: Same rule as the ankle – inability to bear weight immediately and currently.

The Key Takeaway for Ankle/Foot: Pain in the malleolar or midfoot zone plus either specific bony tenderness or inability to bear weight warrants an X-ray series (ankle series or foot series, respectively). If they have pain but none of those other criteria, the likelihood of a significant fracture is very low, and you can likely manage them conservatively.

Moving on to Knee Injuries:

Someone comes in clutching their knee after a fall or a twist. Here, the criteria are a bit different:

1. Age: If the patient is 55 years or older, that's an independent risk factor for fracture.
2. Fibular Head Tenderness: Palpate the head of the fibula – that bony prominence on the outside, just below the knee joint. Isolated tenderness here is significant.
3. Patellar Tenderness (Isolated): Gently feel the kneecap. Tenderness only on the patella, without tenderness elsewhere around the knee, is a red flag.
4. Inability to Flex: Can they actively bend their knee to 90 degrees? If not, that limited range of motion could indicate a significant injury.
5. Inability to Bear Weight: Just like the ankle and foot, inability to take four steps immediately after the injury and currently is a strong indicator for imaging.

The Bottom Line for the Knee: If any of these criteria are met, you should proceed with a knee X-ray series (AP, lateral, and often a skyline view). If none of these are present in a younger patient with a clear mechanism of injury and the ability to bear weight and flex their knee, you can often avoid immediate radiography and focus on clinical assessment for ligamentous or meniscal injuries.