Ankle & Foot Fractures (Lisfranc, Calcaneus)
- The ankle is a ring (or a mortise): if it breaks in one place from a twisting force, look hard for a second break on the far side.
- A Lisfranc injury is a disruption of the midfoot's keystone joint — easy to miss, and missing it can wreck a foot. The tell is malalignment at the base of the 2nd metatarsal, sometimes with a tiny "fleck" of bone in the gap.
- The calcaneus (heel bone) breaks when you land on it from a height. Measure Böhler's angle — if it flattens out, the heel is crushed.
- Calcaneal fractures travel in bad company: look for the other foot, the spine, and the pelvis, because the same fall hits all of them.
- Normal radiographs do not equal a normal foot. When the story is convincing, the foot still hurts, and the films look fine, the answer is often CT or weight-bearing views.
The foot and ankle are where physics comes to collect its debts. You roll an ankle stepping off a curb, you jump off a ladder you absolutely should not have been on, and the bones underneath do their best to absorb a force they were never designed for. The trick to reading these films isn't memorizing fifty fracture names — it's knowing the two or three injuries that hide in plain sight and quietly ruin lives. Let's hunt those.
The ankle is a ring — think like a pretzel
Here's the single most useful idea for ankle trauma: the ankle behaves like a ring. Picture a stiff pretzel. If you snap a pretzel ring, it almost never breaks in just one spot — bend it hard enough to crack one side and the opposite side gives too. The ankle "ring" is made of the bones (the two malleoli) plus the strong ligaments holding them together.
So when you spot a fracture of one malleolus, your next move is automatic: go look at the other side. A break of the lateral malleolus (the bump on the outside, the bottom of the fibula) plus tenderness or widening on the inside means the ring failed in two places, even if you only see one fracture. That hidden second injury can be a torn ligament rather than a visible crack — which is exactly why it gets missed.
The joint itself is called the mortise — the same word a carpenter uses for the snug square socket a tenon slots into. On a good mortise view, the gap of joint space around the talus should be uniform all the way around, like a clean grout line around a bathroom tile. If one side of that gray line is wider than the rest, the ankle has shifted, and that's unstable until proven otherwise.
A single fibular fracture with a widened medial joint space is a two-part injury of the ring. Treat the gap you can see as evidence of the ligament tear you can't.
Lisfranc: the midfoot's keystone
Now the sneaky one. The Lisfranc joint is the row of joints where the long metatarsal bones of your forefoot meet the small tarsal bones of the midfoot. The architecture here is genuinely clever: the second metatarsal is recessed back into a notch like the keystone at the top of a stone archway. Pull that keystone and the whole arch loses its integrity.
A Lisfranc injury is a disruption of that lineup — sometimes an obvious fracture-dislocation, but often something far subtler from a twist on a planted foot. The classic radiographic tells:
| Sign | What you're looking for |
|---|---|
| Malalignment | The inner edge of the 2nd metatarsal base should line up perfectly with the inner edge of the middle cuneiform. If it steps off, that's the injury. |
| "Fleck" sign | A tiny chip of bone floating in the gap between the 1st and 2nd metatarsal bases — an avulsed piece of the Lisfranc ligament. |
| Gap | Abnormal widening between the 1st and 2nd metatarsal bases. |
The most dangerous Lisfranc injury is the one that looks normal at rest. The bones can sit back in place on a non-weight-bearing film and only splay apart when the patient stands. If the story fits and the foot is swollen and bruised across the midfoot, push for weight-bearing views or CT before you call it normal.
The calcaneus: jump, crush, and look elsewhere
The calcaneus is your heel bone, and it usually breaks one way: an axial load, meaning you fell from a height and landed on your feet. Think of a soda can taking the full weight of someone stepping on it — it crumples and bulges outward rather than snapping cleanly.
The measurement to know is Böhler's angle, drawn on the lateral view between two lines along the top contour of the calcaneus. In a normal heel it's a comfortable upward angle; when the bone is crushed, the angle flattens (and can even go negative). A low Böhler's angle is your quantitative proof that the heel has collapsed.
A calcaneal fracture is a flare announcing that a serious fall happened — and serious falls don't stop at the heel. The same axial force travels up the skeleton, so deliberately check the other calcaneus, the spine (especially the thoracolumbar junction), and the pelvis. The dramatic, painful heel can steal all your attention while a quiet spine fracture rides along unnoticed.
Tying it together
When you're handed a sore ankle or foot, run the mental checklist: With ankle injuries, treat the joint as a ring and chase the second break. With midfoot pain after a twist, interrogate that 2nd metatarsal line and don't trust a resting film — get weight-bearing views. With a heel crush, measure Böhler's angle and immediately go shopping for fractures in the spine and pelvis.
These all reward the same humility: a normal-looking radiograph is not the same as a normal foot. When the mechanism and the exam are screaming but the films are quiet, that's your cue to escalate — to weight-bearing views, to CT, sometimes to MRI for stress fractures that haven't shown up on plain film yet. And before you describe any of these, it's worth being fluent in how to describe a fracture — because a precise description is what gets the foot to the right surgeon. (Kids play by their own rules here; their growth plates change the whole game in pediatric fractures.)
The foot is small, the stakes are large, and the worst injuries are the politest about announcing themselves. Stay suspicious.