Epiphysis: Understanding Bone Growth at the Ends of Bones

The epiphysis (plural: epiphyses) is the expanded end of a long bone where longitudinal growth occurs. It is located at the ends of bones such as the femur (thigh), humerus (upper arm), tibia, and radius.

Types of Epiphyses

• Primary Epiphyses: Formed during embryonic development; responsible for the majority of bone lengthening during childhood.
• Secondary Epiphyses: Develop later in childhood; fine-tune bone shape and size, and form articular surfaces.

Growth Mechanism

Growth in length occurs at the epiphyseal plate (growth plate), a layer of hyaline cartilage between the epiphysis and the metaphysis (shaft). Chondrocytes in this plate proliferate, mature, and are replaced by bone, lengthening the shaft.

Epiphyseal Closure

During late adolescence, the epiphyseal plate ossifies (closes), fusing the epiphysis to the metaphysis. This epiphyseal closure marks the end of longitudinal bone growth. The timing varies by bone and sex, generally completing by ages 18–25.

Injuries to the growth plate in children can disrupt normal bone development, requiring careful management.