The<unk><unk>  is a true diarthrodial<unk>  that<unk>  the sacrum to the pelvis. The sacrum connects on the right and left sides to the ilia (pelvic bones) to form the<unk><unk> s. The pelvic girdle is made up of two innominate bones (the iliac bones) and the sacrum. The innominate bones<unk> in the front of the pelvis to form the pubic symphysis, and at back of the sacrum to form the<unk>  (SI)<unk> s. Each innominate bone (ilium)<unk>  the femur (thigh bone) to form the hip<unk> ; thus the<unk><unk>  moves with walking and movement of the torso. In this<unk> , hyaline cartilage on the sacral side moves against fibrocartilage on the iliac side. The<unk><unk>  contains numerous ridges and depressions that function in stability. Studies have documented that motion does occur at the<unk> ; therefore, slightly subluxed and even locked positions can occur. Muscles and ligaments surround and attach to the SI<unk>  in the front and back, primarily on the ilial or sacral surfaces. These can all be a source of pain and inflammation if the SI<unk>  is<unk> al. The<unk><unk>  is highly dependent on its strong ligamentous structure for support and stability. The most commonly disrupted and/or torn ligaments are the iliolumbar ligament and the posterior<unk>  ligament. The ligamentous structures offer resistance to shear and loading. The deep anterior, posterior, and interosseous ligaments resist the load of the sacrum relative to the ilium. More superficial ligaments (e.g., the sacrotuberous ligament) react to dynamic motions (such as straight-leg raising during physical motion). The long dorsal<unk>  ligament can become stretched in periods of increased lumbar lordosis (e.g., during pregnancy). Affected muscle groups Many large and small muscles have relationships with the ligaments of the<unk><unk>  including the piriformis (see “piriformis syndrome”, a condition often related with<unk> , rectus femoris, gluteus maximus and minimus, erector spinae, latissimus dorsi, thoracolumbar fascia, and iliacus. Any of these muscles can be involved or spasm with a painful and<unk> al<unk><unk> . The SI<unk>  is a pain-sensitive structure richly innervated by a combination of unmyelinated free nerve endings and the posterior primary rami of spinal segments L2-S3. The wide possibility of innervation may explain why pain originating from the<unk>  can manifest in so many various ways, with different and unique referral patterns (see “referred pain”) for individual patients. Patients with<unk>  can also develop tightness and<unk>  in the hamstring, quadriceps, iliotibial tract (see “iliotibial band syndrome”) and hip flexors, including the psoas muscle. Individuals with severe and long-standing<unk>  can develop muscle deconditioning and atrophy throughout the body due to limitation of activities and exercise that bring about pain in the low back.
Sacroiliac joint dysfunction
Radicular pain
Pelvic girdle pain
Jaw claudication
Back pain
Tendinopathy
Low back pain
Xiphodynia