When people ask when hips stop growing, they are referring to the cessation of skeletal development in the pelvis. The pelvis is a complex of bones that forms the foundation of the upper body. The timing of this process varies significantly among individuals, largely depending on the progression of puberty. The pelvis is notably one of the last major skeletal structures to complete its growth and fusion, marking the end of the body’s vertical growth phase.
The Skeletal Mechanism of Hip Growth
The bony pelvis is composed of three paired bones that fuse together: the ilium, the ischium, and the pubis. These three bones meet in the center to form the acetabulum, the cup-shaped socket that holds the head of the femur, creating the hip joint. Throughout childhood and adolescence, these bones remain separate at their junctions by sections of cartilage known as growth plates.
The growth of the bony pelvis is driven by a specialized Y-shaped structure of cartilage called the triradiate cartilage, located deep within the acetabulum. New bone tissue is formed at this cartilage, allowing the hip socket to expand in size and depth. This process of bone formation, called endochondral ossification, lengthens and widens the bones until hormonal signals halt the process. The overall size of the pelvic bones is determined by the duration and intensity of this growth phase.
General Timeline for Skeletal Maturity
The cessation of hip growth is defined by the permanent fusion of the various growth plates in the pelvis. The triradiate cartilage is one of the first major hip growth plates to complete its fusion, which typically occurs in mid-adolescence, between 13 and 16 years of age. Once this central cartilage has turned entirely to bone, the primary growth of the hip socket is complete.
However, other secondary growth centers on the pelvis, such as the epiphyseal plates of the iliac crest (the top ridge of the hip bone) and the ischial tuberosity, close later. These plates can remain active and unfused until the late teens or early twenties. After all these cartilage plates have completely ossified, linear growth of the hip bones permanently stops, often concluding the final skeletal maturity of the pelvis around 18 to 25 years old.
Hormonal Influence on Pelvic Shape
While the general timeline for growth cessation is similar, sex hormones cause a profound remodeling of the pelvis that results in distinct shapes between males and females. This pubertal reshaping is arguably a more significant event than the final lengthening of the bone. The onset of puberty triggers a divergence in the developmental trajectory of the pelvis.
In females, the dramatic rise in estrogen levels during puberty drives a specific pattern of bone remodeling that widens the pelvis and creates a broader, shallower structure. This widening is a biological adaptation to facilitate childbirth. The female pelvis, often classified as the gynecoid shape, features a wider pelvic inlet and a larger, more open subpubic angle.
Conversely, the rise of testosterone in males causes the pelvis to follow a more direct continuation of the prepubertal growth pattern, resulting in a narrower, taller, and more heart-shaped structure. The male pelvis, typically classified as android, has a more acute subpubic angle and a deeper pelvic cavity. This difference in hormonal signaling during adolescence is responsible for the characteristic skeletal width that distinguishes the adult male and female hips.
Factors Determining Final Hip Size
The final size of the bony pelvis is a fixed measurement once all growth plates have fused, but this skeletal width is only one component of a person’s overall hip size. Genetics play the predominant role in determining the final dimensions of the bone structure. A person’s inherited skeletal blueprint sets the limits for how wide or narrow their pelvic bones will ultimately be.
Nutrition during the growth phase also exerts a significant influence on achieving this genetic potential. Adequate intake of calcium and Vitamin D is necessary for optimal bone mineralization and mass acquisition throughout childhood and adolescence. Insufficient levels of these nutrients can compromise the density and structure of the bone tissue, even if the general shape and length are genetically determined.
The overall circumference of the hips is greatly influenced by soft tissues, particularly gluteal muscle mass and the distribution of subcutaneous fat. While the bone structure stops growing in the early twenties, muscle mass and fat distribution continue to change throughout a person’s life in response to diet, exercise, and hormonal fluctuations. Therefore, a person’s hip appearance can still be significantly modified long after their skeletal growth has ceased.