If you aren't sure, I would call up the vet and make an app. it is a possibility that its broken or its just MBD. Hope your find out what it is. Good Luck! Hope someone else that has more experience with this can help you.
It sure looks wrong. An Xray /vet exam will tell you whats going on. Does the lizard walk on it? any weakness climbing? Check Uvb output and calcium D3 scheduled dusting.
A blood sample will determine if its a calcium related issue and you can take steps to correct it if so, before it worsens.
Does the lizard fall at all?
Definately call around your local vets and ask specifically if they deal with reptiles, more specifically chameleons. Its a really good idea to bite the bullet and see a vet now before this becomes much worse.
This is solid advice despite a lack of indepth info about your lizard and setup.
Vet first, however, as soon as possible, especially if your new to chams, please find the health/setup questionair at the top of the health forum and cut n paste your answers as completely as possible so we can help you out some more with some setup tips.
Can you fill in the "how to ask for help" form that is stickied on this forum - copy and paste it into a reply on here and fill in the info - there is def. something wrong, it looks rather like my chams leg - he has MBD and multiple fractures. A vet visit is required and an x-ray at least. If you can fill in the how to help form, we can advise you as far as your husbandry goes etc.