The ankle joint is comprised of four bones: the tibia, the fibula, the talus, and the calcaneus. The tibia and the fibula are the bones which support the lower leg from the knee to the ankle. The talus and the calcaneus are the two bones that provide the bony structure in the heel and part of the instep. For the purposes of this article, we're only going to focus on the tibia and the fibula. The talus is often involved in ankle injuries, but usually it's the tibia and fibula that contribute to the fractures encountered in contact sports. The calcaneus can be ignored at this point as well because it is fairly difficult to break; its most common clinical presentation involves falls of over 20ft with the patient landing on his heels.
So, on to the tibia and fibula. When most people think of their ankles, they are usually thinking about the bony protuberances right above their heels. We call each of these a malleolus; the tibia has one and so does the fibula. The tibia, being closer to the midline and the instep, is medial to the fibula, and therefore we call its malleolus the medial malleolus. The fibula ends in the lateral malleolus on the outer part of the ankle.
There are a number of ligaments that hold this joint together. To simplify, we will only talk about one of them: the deltoid ligament. This ligament connects medial malleolus to the talus. The deltoid ligament is quite remarkable for its strength, and the clinical importance of this will be made apparent shortly.
Most ankle fractures happen as the foot is either everted or inverted beyond its normal limits. Eversion is the foot rotating laterally such that the sole of the foot faces outward away from the body (red arrow). When this happens, the medial malleolus is fractured (red star). Here's where things get interesting. Recall our discussion a while back on knee injuries. In that article we talked about a similar force applied to the knee, and as a result, the ligaments tore, but the bone didn't break. Because the deltoid ligament is so much stronger than the MCL, for example, the ligament in an ankle eversion doesn't tear. Instead, it rips the most distal piece of the medial malleolus off of the end of the tibia. We call this type of injury when a bone is shorn apart an avulsion fracture.
The opposite happens when the foot is inverted i.e. when the foot rotates such that sole is pointing toward the midline (blue arrow). In this type of injury, the lateral malleolus of the fibula is fractured (blue star). This happens as a direct effect of the inversion because the ligaments on that side of the foot are not nearly as strong as the deltoid. This results in a more traditional kind of fracture and an increased likelihood of ligament tears on the lateral aspect of the ankle. While he did fracture his fibula, this is NOT how it happened to Malik Zaire, however. Let's look at the tape (start at 2:25):
We can notice that his foot becomes trapped under the rear end of number 38. In the below image we see the blue arrow indicates the long axis of the foot, from heel to toe. The red arrow indicates the long axis of the leg (based on what we can see of the knee). It is a little tough to show in two dimensions, but the red arrow and the blue arrow should be roughly parallel under normal conditions. All this means is that when a person is walking or running, his kneecap and his big toe should point in roughly the same direction. As we can clearly see from the image, Malik's foot is perpendicular to the direction it should be pointed (dotted blue line). It was the torque applied to the foot, which was translated to the fibula, that caused the fracture of the fibula.
At first I was certain that I was looking at a tibial fracture. It looked like the foot had everted and at the moment of injury it looked as if the tibia had given out and fractured. Upon further inspection, and noticing the orientation of the foot, it became clear that the foot had torqued clockwise (dotted blue arrow around ankle) and what we witnessed was the fibula giving way and allowing for further rotation around the ankle joint.
All in all, this injury looks a lot worse than it really is, and for that we should be thankful. The guidelines for fibula fractures for athletes suggest about 3-4 weeks in a cast or splint. That would be followed by a few weeks of rehab. Full training can resume usually as early as 8 weeks. This timeline can sometimes be accelerated, especially if the injury is uncomplicated. The decision to accelerate the timeline must be weighed, however, against the possibility of re-fracturing the bone, which would be a major set-back to any timely recovery. Malik will most likely be out for the whole season. The good news is that he has more than enough time to recover for the spring.
At the end of the day, this was another freak accident and a continuation of a run of bad luck for the Fighting Irish. It took a player falling on his foot while it was in such a vulnerable position and at a precise moment in his stride to take down Malik Zaire. We can only pray at this point that the chips start falling our way as this season progresses and for a swift and complete recovery for number 8.