The hip joint is a synovial joint formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis. It forms the primary connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis. Both joint surfaces are covered with a strong but lubricated layer called articular hyaline cartilage.
The cuplike acetabulum forms at the union of three pelvic bones — the ilium, pubis, and ischium. The Y-shaped growth plate that separates them, the triradiate cartilage, is fused definitively at ages 14–16. It is a special type of spheroidal or ball and socket joint where the roughly spherical femoral head is largely contained within the acetabulum and has an average radius of curvature of 2.5 cm. The acetabulum grasps almost half the femoral ball, a grip augmented by a ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator. The joint space between the femoral head and the superior acetabulum is normally between 2 and 7 mm.
The head of the femur is attached to the shaft by a thin neck region that is often prone to fracture in the elderly, which is mainly due to the degenerative effects of osteoporosis.
The acetabulum is oriented inferiorly, laterally and anteriorly, while the femoral neck is directed superiorly, medially, and slightly anteriorly.
- The transverse angle of the acetabular inlet (also called Sharp's angle and is generally the angle referred to by acetabular angle without further specification) can be determined by measuring the angle between a line passing from the superior to the inferior acetabular rim and the horizontal plane; an angle which normally measures 51° at birth and 40° in adults, and which affects the acetabular lateral coverage of the femoral head and several other parameters.
- The sagittal angle of the acetabular inlet is an angle between a line passing from the anterior to the posterior acetabular rim and the sagittal plane. It measures 7° at birth and increases to 17° in adults.
- Wiberg's centre-edge angle (CE angle) is an angle between a vertical line and a line from the centre of the femoral head to the most lateral part of the acetabulum, as seen on an anteroposterior radiograph.
- The vertical-centre-anterior margin angle (VCA) is an angle formed from a vertical line (V) and a line from the centre of the femoral head (C) and the anterior (A) edge of the dense shadow of the subchondral bone slightly posterior to the anterior edge of the acetabulum, with the radiograph being taken from the false angle, that is, a lateral view rotated 25 degrees towards becoming frontal.
- The articular cartilage angle (AC angle, also called Hilgenreiner angle) is an angle formed parallel to the weight bearing dome, that is, the acetabular sourcil, and the horizontal plane, or a line connecting the corner of the triangular cartilage and the lateral acetabular rim.
yes this is from wikipedia (cause it's free) and a quick overview, but not inclusive https://en.wikipedia.org/wiki/Hip