Dr. Kevin Lam: Popping peroneal syndrome on an 11 year-old child with classic symptoms. Basically, popping peroneal syndrome is when kids or adults come in complaining about “Hey, I feel a bone pop behind the ankle”. This is the grove where the peroneal tendons are supposed to be. The peroneal tendons are on the lateral or the outside of the ankle. So this is going to be right here on this side.

The tendon is supposed to run behind the fibula, come around, one attaches here, the other one goes underneath the foot and goes and attaches down here, so the two peroneal tendons.

Now, when we feel the pop, that tendon lies in front of this bone and it pops in front and that’s where that happens. A couple of different reasons why that happens is one, either the groove is too shallow, that’s one way. This is supposed to have a little pit, almost a “c” shaped groove in the back which this bone model shows a little bit right here. Some kids are born with ones that are too shallow.

Another thing is — a less likely cause is patients are born with that tissue that holds it in being too weak. If that is too weak, we can still go ahead and repair that. An MRI will give us an idea of, if the groove is too shallow, we can go ahead and fashion a groove right here with a little bore, make it a deeper “c” shape and then reinforce and replace the tendon behind so that it won’t pop.

So now to the patient, here’s how we could tell. This is the fibula right here and this is the tendon that runs right behind it. This is the fibula outline and this is the tendon right here. Good anatomy lesson, this the peroneal tendon.

Now I’m going to have you put your toes over to that wall for me, okay? Point over there. Okay. As she points, we’re going to see this tendon bowstring, this tendon bowstring… relax… this tendon is going to bowstring to the side of the fibula. Point that way again, one more time. And that’s what causes the pop.

Dr. Kevin Lam: As you can see this tendon is very, very prominent, right here now. If I could see it right there, push, push, push, push… right here, it’s almost on the side of the fibula, right now. Relax. Now, tendon relocates. Now push again.  The tendon comes out to the side again right here. And that’s what the pop is.
Patient: Mhmm.

Dr. Kevin Lam: It’s more pronounced on the other side, but it’s harder to see. We’re going do it one more time. This is the peroneus brevis tendon, I’m tracing it from here to here, inserts into the base of number five.

You’re going to relax for me for one more time, we’re going to… right there. See that tendon? Just by doing that without her doing any force, this is called the peroneal tendon stress test. So I dorsiflex, make you do something called evert, so I dorsiflex and evert and this tendon would dislocate up front to the side. And I can feel a pop. You can hear the audible pop right now. I’m reproducing the pop.

Dr. Kevin Lam: Is that what you hear when you walk?

Patient: Yes.

Dr. Kevin Lam: That’s the peroneal tendon dislocation, peroneal popping syndrome. I can feel my hand and she could hear it and you can hear it at home, this popping sound from her tendon.

Now sometimes patients have a tear on this tendon, that’s what the MRI is going to tell us too. If there’s a tear, again, we could repair and replace it back. So there’s a couple of different things that can cause this. Number one, we went over the shallow grove, back here,  if it’s too shallow, that tendon can pop forward. Or if a patient has a tear in that tendon, it can pop forward. Or if the ligament – there’s a ligament that holds this behind called the peroneal retinaculum, it hold this tendon back. If she was born with a weakened ligament back here, that can also cause that tendon to pop forward. Now, the chance of her having a tear back here being the primary cause is fairly low because she has it on both sides. So most likely, one of the congenital deformities that was causing this popping to happen. So an MRI will be ordered, we’ll figure it out and we’ll come up with the best choice of care.

Dr. Kevin Lam: Any questions?

Patient: No.

Dr. Kevin Lam: Okay, good.