Asana Anatomy -The Sacroiliac Joint
By Dr. Robin Armstrong • August 28th, 2008 • 12350 Views
Stepping your legs wide, bowing gracefully into Prasarita Padottanasana (wide legged forward bend) for the fourth time this class, you finally glimpse the floor close to the top of your head. You finish your yoga practice feeling great, until a slow dull ache develops at the base of your spine, and gradually turns into sharp, shooting pains when you walk.
What happened? You can't recall a specific event, yet yoga is the only thing you did that might have contributed to this mysterious pain. In fact, your beautiful wide legged forward bend may have contributed to you spraining your sacroiliac joint.
Let's dissect this joint.
The two sacroiliac joints (SI joints) are formed by three bones: the triangular sacrum bone at the base of the spine, and the two wing like bones of the pelvis known as the ilium. Each iliac bone (one half of the ilium) comes in contact with one side of the sacrum, forming two SI joints. Like all of the joints of the body, the SI joints are contained by a joint capsule of connective tissue, and bathed in nourishing synovial fluid.
In the front, the joint capsule is covered with the sacroiliac ligament, and in the back the capsule blends with the deep intterosseus ligament. In addition there are more supportive ligaments: the sacrotuberous ligament from the ischial tuberosity (sitting bone) to the sacrum, the sacrospinous ligament which attaches from the ilium and connects to the sacrum, and the iliolumbar ligament with attachments in the lumbar spine and the ilium.
All of these ligaments can provide a lot of support, but also provide the opportunity for injury. To review our anatomy for a moment, ligaments attach bone to bone, and tendons attach muscle to bone. We sprain a joint or ligament, and we strain a muscle or tendon.
Ligaments are meant to be supportive structures, which are generally inflexible. In women who have been pregnant, a hormone called relaxin causes the ligaments to relax to prepare for childbirth, and this effect is global throughout the body. Sometimes this ligamentous freedom can stay, to a smaller degree, after the child is born. In general, women's ligaments are affected by the hormone fluctuations of their menstrual cycles, and have more ligamentous flexibility than males. ...