Answer:
Osteoblast activity in connective tissue.
Explanation:
Osteoblasts are cells that are in the bones, and they are the ones that produce new bone tissue under the influence of vitamin D and hormones. People with Fibrodysplasia ossificans have a lot of osteoblasts in the connective tissue, which is the one that is predominant in ligaments and tendons with collagen fibers that give elasticity and resistance. When they damaged this tissue, the osteoblasts that are present there, produce bone tissue losing the flexibility of the joint.