How big is the plantar plate ligament? Well, great question and that is what we’re talking about today on the Doc On The Run Podcast.
I was just on a consultation call, it was actually a webcam call with a runner who has had a plantar plate injury. One of the things we were doing was we were reviewing her MRI and one of the first things I did was check to see how big the slices were on the MRI.
As soon as I said, “Hold on, I got to see how big your slices are”, She said, “What are my slices?” and I explained to her, I said, so I actually held up a foot model, this one, and I said, the slices are where the MRI takes pictures. So, if you have a slice here, and you have a slice here, and you have a slice here, but you only had those three slices, you would miss a lot of stuff.
In fact, if you had a slice here and one out here, you would miss all of the plantar plate and then she asked me a valid question. She said, “Well, how big is the plantar plate ligament?” because a lot of times, in fact, well, in her case, the MRI was two-millimeter slices. Sometimes they’re one and a half millimeters, sometimes two, sometimes three and a half, sometimes four.
There can be a wide variation on how tight those cuts are where the MRI imaging machine is taking those pictures. So, there is, believe it or not, there’s research that shows how big the plantar plate ligament usually is. And this comes from a study on, the title of it was metatarsophalangeal joint stability, a systematic review on the plantar plate of the lesser toes. It was in the Journal of Foot and Ankle Research. I’ll put a link in the show notes or a reference to it so that you can look it up if you’re interested in reading this.
But how big is it? Well, they’re basically, obviously, there’s three dimensions, right? So, in terms of how wide it is, like width meaning from medial to lateral or from right to left, depending on how you’re looking at it, on that size, the average size is about eleven millimeters. So, eleven millimeters, that’s 1.1 centimeters, it’s not very big. The whole range in that study was eight to thirteen millimeters wide.
In terms of length, meaning proximal to distal, like from the bottom of your foot out toward the toes. So, it starts actually, the origin is on the base of the proximal phalanx, and then it comes down and attaches to the base or the head and neck of the second metatarsal. Well, in terms of length that direction, it’s about nineteen millimeters long with the range being sixteen to twenty three millimeters in that length. Then in terms of thickness, when you stand on it from the ground up to your foot, how thick is it? Well, it’s not very thick, turns out. There’s a bigger range there. So, two millimeters to five millimeters is the thickness of the plantar plate ligament.
Why is that important? Again, okay, let’s say that you had a two-millimeter-thick plantar plate ligament, and you got slices that were three and a half. Three and a half, you could completely miss it because you’d have one slice here and then three and a half millimeters later, you’d have a slice or image on the other side of the plantar plate ligament.
In that case, you might not see it at all because the slices are way too big. So, certainly getting slices that are two millimeters increases the probability you’ll actually see it at all when you look at that particular view. It also increases the odd that you see more of it in these other views, meaning that direction and this direction as you take those slices with the MRI machine across the foot.
So, there you have it. In size of the plantar plate ligaments, about two to five millimeters thick, it’s about nineteen millimeters long, it’s about eleven millimeters wide. So, it’s not very big, but it is very important, and it causes a lot of pain in the ball of the foot of runners who sprain, stretch, or strain that ligament.
If you want to learn more about the strategies I use that runners get when they get that injury and want to get back to running, I talk about all those strategies and deep dive into those particular strategies in the plantar plate masterclass, which you can get for free at www.docontherun.com/plantarplatemasterclass. So, come sign up and I’ll see you in the training.
Reference:
Maas, N.M.G., van der Grinten, M., Bramer, W.M. et al. Metatarsophalangeal joint stability: a systematic review on the plantar plate of the lesser toes. J Foot Ankle Res 9, 32 (2016). https://doi.org/10.1186/s13047-016-0165-2
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