There are two shin bones and if they fuse there is a lack of mobility. A lot of muay Thai fighters have problems with their legs later on. That in addition to the obvious which is brain damage and a lot of scar tissue in the face.

Interesting, thanks.

Can you point to a solid source on this? Googling tibia fibula synostosis muay thai, and similar, doesn't turn up anything relevant to conditioning.

I knew some fighters. One of them was a low kick specialist and his shin felt like one solid piece of concrete. Not sure if it was fused but he couldn’t do certain movements , but he could kick with unbelievable force. I have no idea how his opponents could block this with their own shins. Many years later I still have some sensitive spots on my shins from trying to train with them. It was impossible.

Huh, I had never even thought of the tibia and fibula fusing, does this really happen often in Muay Thai? I coincidentally just got back from training at my Muay Thai gym just now. The first few weeks or months of training there’s definitely a lot of welting on the legs, but the shins adapt quickly. I hadn’t heard of the shin bones fusing.