What does epiphysis mean?
An epiphysis is the rounded end of a long bone such as the femur, tibia, or humerus, distinct from the central shaft, which anatomists call the diaphysis. During childhood and adolescence, each epiphysis develops from its own centre of bone formation and is joined to the shaft by a layer of cartilage known as the epiphyseal plate, or growth plate. This cartilaginous junction is where longitudinal bone growth occurs, making the epiphysis central to paediatric orthopaedics: injuries here, such as a slipped capital femoral epiphysis, can affect a child's future growth and limb alignment. Once growth is complete, usually in the late teens or early twenties, the plate ossifies and the epiphysis fuses permanently with the diaphysis. The term belongs to formal medical and scientific register and appears chiefly in anatomy texts, radiology reports, and forensic work, where the state of epiphyseal fusion helps estimate age from skeletal remains. Its plural is "epiphyses," and the adjective form is "epiphyseal."
nounThe end portion of a long bone, which develops from a separate centre of ossification and is joined to the bone shaft (diaphysis) by the growth plate.
- The expanded end of a long bone, formed from a secondary ossification centre and separated from the diaphysis by the epiphyseal plate during growth.
"In adolescents, the epiphysis remains separated from the shaft by cartilage until skeletal maturity is reached."
"A slipped capital femoral epiphysis can cause pain in the hip or knee of an adolescent."
"Radiographs showed the epiphysis had not yet fused with the diaphysis, indicating continued bone growth."
Standard Greek-derived plural; pronounced /ɪˈpɪfɪsiːz/. Used when referring to multiple bones or both ends of one bone.
"The radiologist noted open epiphyses at both wrists, consistent with an adolescent patient."
Your thigh bone was once several separate bones: the epiphyses only fuse to the shaft in your late teens, which is why X-rays of children's legs show lines doctors must learn to read as growth plates rather than fractures.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of epiphysis
"Epiphysis" derives from the Greek "epiphysis," meaning "a growing upon," formed from "epi-" (upon) and "physis" (growth, nature), itself from the verb "phyein," to grow. The term entered English anatomical usage in the early modern period, in the seventeenth century, as classical Greek terminology was adopted for descriptive anatomy. It shares its root with the closely parallel anatomical terms "diaphysis" (the shaft, literally "a growing between") and "apophysis" (a bony outgrowth), and more distantly with words like "physics" and "physiology," all tracing back to the same Greek root concerning nature and growth.
Related word forms
How epiphysis is actually used
"Epiphysis" is a technical term used almost exclusively in anatomy, medicine, radiology, and forensic science. It is formal register and would rarely appear outside professional or educational contexts. The plural "epiphyses" follows Greek-style declension, as does the related adjective "epiphyseal."
Easily confused with epiphysis
An apophysis is a bony projection or outgrowth that serves as a site for tendon or muscle attachment, whereas an epiphysis is the rounded end of a long bone involved in joint formation and longitudinal growth.