Anatomy, Bony Pelvis and Lower Limb: Pelvic Joints

Excerpt

The pelvis joints include the pubic symphysis and the lumbosacral, sacroiliac, and sacrococcygeal joints. The bony pelvis also articulates with the lower limb via the acetabulofemoral, or hip, joint on its lateral aspect. The lumbosacral joints include multiple articulations of the fifth lumbar vertebra (L5) and the first sacral element (S1). There is an intervertebral (IV) joint between the vertebral bodies of the fifth lumbar vertebra and the first sacral vertebra with an interposed intervertebral disc. In addition, there are two articular, or zygapophyseal, joints serving as an articulation between the L5 and S1 articular processes. The sacroiliac joint is a bilateral compound joint, with synovial and syndesmotic portions, that serves as an articulation between the auricular surfaces of the ilium and sacrum and their tuberosities. This joint transmits a significant amount of the weight of the upper extremities and torso to the lower limbs, which serves to explain the unusually restricted mobility of this partly synovial joint.

The sacrococcygeal joint is an articulation between the fifth sacral element (S5) of the sacrum, the first coccygeal vertebra (Co1) of the coccyx, and the intervertebral disc between them. Finally, the pubic symphysis is an anteroinferior and midsagittal fibrocartilaginous pelvic joint serving as the articulation for the right and left pubic bodies. The pubic symphysis is covered in hyaline cartilage and is somewhat moveable. The pelvic joints are variable in their degree of movement and contribute to the transmission of forces through the pelvic girdle and the lower limbs. The pelvic joints are reinforced by several ligaments, some of which include the sacrotuberous, sacrospinous, and iliolumbar ligaments. The ligaments supporting the pubic symphysis are flexible and further relaxed during pregnancy due to an increase in relaxin and other hormones. Understanding the basic anatomy of the pelvic joints and ligaments has significance in obstetrics, orthopedics, sports medicine, emergency medicine, and numerous other clinical fields.