The lumbosacral joint is a joint of the body, between the last

lumbar vertebra The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...

and the first

sacral segment The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spin ...

of the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...

. In some ways, calling it a "joint" (singular) is a misnomer, since the lumbosacral junction includes a disc between the lower lumbar vertebral body and the uppermost sacral vertebral body, as well as two lumbosacral facet joints (right and left

zygapophysial joint The facet joints (or zygapophysial joints, zygapophyseal, apophyseal, or Z-joints) are a set of synovial joint, synovial, plane joints between the articular processes of two adjacent vertebrae. There are two facet joints in each functional spin ...

s).

References

Bones of the vertebral column Sacrum {{musculoskeletal-stub