Wednesday, September 21, 2011

A Lateral Ankle Tendon: Peroneus Longus or Peroneus Brevis?

Hello! Just a quick post today to give you a taste of the extra anatomy information you can now get at the new Human Anatomy for the Artist Facebook page! Yep, I have a Facebook page now, on which I'll post links to all the full lessons that are normally seen on this blog, as well as other links, photos, book recommendations, and quick mini-lessons like the one below.

This will allow those who don't use Blogger (and those who use Blogger but don't check it often) to get updates on a more regular basis. The Blogger posts, after today, will resume their usual format of longer, more elaborate lessons.

So... today's mini-lesson is about a tendon seen on the lateral ankle and foot. Or is it two tendons? Let's take a look:

When drawing the lateral side of the foot, you'll almost always see a tendon up above (proximal to) the lateral malleolus of the fibula, which is a bony bump on the lateral side of the ankle. Sometimes, though, when the foot is everted (sole turned outward) and/or plantarflexed (toes pointed downward) you'll see what appears to be a continuation of that tendon down below (or distal to) the lateral malleolus. The whole thing really looks like one long tendon wrapping around the back of the malleolus. But... you guessed it. It's not!

What we're seeing here is actually two different tendons. The tendons of both the peroneus longus muscle and the peroneus brevis muscle wrap around the back of the lateral malleolus, but here's the weird thing. The peroneus longus tendon disappears right around the time it reaches the lateral malleolus. At that point, the peroneus brevis tendon emerges and continues its course along the lateral side of the foot. But the transition is so smooth that it looks like a single tendon both proximal to and distal to the lateral malleolus.

In drawing, the difference is that you'll almost always see the peroneus longus tendon, but the peroneus brevis tendon will usually only show when the foot is everted or plantarflexed.

One more thing: Some books call the peroneus longus and brevis tendons by a different name: fibularis longus and brevis. So if you see this, it isn't wrong. It's just an alternate name. Sometimes that happens in Anatomy. I guess it keeps things interesting.

We'll have a more detailed lateral leg post, complete with diagrams, soon!

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