Which condition results from the abnormal proliferation of osteogenic cells within soft tissue?

Heterotopic ossification is characterized by the abnormal proliferation of osteogenic cells in soft tissue, leading to the formation of bone in places where bone is not typically found. This condition can occur in various settings, such as after trauma, surgery, or as a result of neurological conditions. The key aspect of heterotopic ossification is that it involves the inappropriate development of bone outside the normal skeletal system, disrupting normal tissue structure and function.

In contrast, fibrosis pertains to the excessive formation of connective tissue, not specifically ossification or bone formation. Cartilage degeneration refers to the breakdown or degradation of cartilage, which is a different process from the formation of new bone. Osteopenia is a condition characterized by lower than average bone density but does not involve the abnormal proliferation of osteogenic cells. Thus, the defining feature of heterotopic ossification lies in the abnormal development of bone tissue within non-skeletal areas, making it the correct answer.