Periosteal

Periosteal refers to the periosteum, the dense membrane that covers most bones, with the exception of articular surfaces. The periosteum has two layers: an outer fibrous layer and an inner cambial (osteogenic) layer. The outer layer contains fibroblasts and collagen and serves as an attachment site for tendons and ligaments, while the inner layer harbors progenitor cells capable of differentiating into osteoblasts and contributing to bone growth and repair.

The periosteum is highly vascularized and innervated. Blood vessels enter bone through foramina and perforating fibers, supplying cortical bone and the inner bone tissues. Sensory nerves in the periosteum convey pain, making it a common source of discomfort in injuries and inflammatory conditions.

In growth and healing, the periosteum plays a central role. In children, the cambial layer is especially active, supporting appositional growth and rapid repair. In adults, periosteal activity declines but it remains important for fracture healing, providing osteogenic cells and a vascular conduit for callus formation along the bone surface.

Clinical relevance includes periosteal reactions, which are radiographic signs of subperiosteal new bone formation in response to trauma, infection, or neoplasia. Periosteal involvement is also considered in various surgical contexts, where periosteal stripping, grafts, or flaps may be used to access or reconstruct bone, and where periosteal response informs prognosis and treatment planning.