Osteoarthritis is the most common joint disorder caused by wear and tear on the joint. It tends to run in families. Other risk factors include being overweight, fractures or other joint injuries in the past, long-term overuse.
To my knowledge, I don't think scientist have identified a gene that is linked to predisposition to osteoporosis.
Bone is a dynamic tissue that is remodeled throughout life. Bone cells called osteoclasts begin the process of remodeling by dissolving or resorbing bone. Bone-forming cells called osteoblasts then synthesize new bone to replace the bone that was resorbed. During normal growth, bone formation exceeds bone resorption. Osteoporosis may result when bone resorption chronically exceeds formation
Calcium absorption occurs in the intestinal tract by two mechanisms, active and passive cellular absorption. Adequate amounts of vitamin D are essential for adequate calcium absorption.
Treatment for osteoarthritis includes medication, physical therapy and surgery, such as joint replacement, realigning bones and fusing bones.