Ischium Posteriorly the ramus forms a large swelling, the tuberosity of the ischium, where the hamstrings originate. The inferior ramus of the ischium (ascending ramus) is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line. The outer surface is uneven for the origin of the obturator externus and some of the fibers of the adductor magnus; its inner surface forms part of the anterior wall of the pelvis. Its medial border is thick, rough, slightly everted, forms part of
Sciatic nerve also innervates muscles. In particular: Pain caused by a compression or irritation of the sciatic nerve by a problem in the lower back is called sciatica. Common causes of sciatica include the following lower back and hip conditions: spinal disc herniation, degenerative disc disease, lumbar spinal stenosis, spondylolisthesis, and piriformis syndrome. Other acute causes of sciatica include coughing, muscular hypertension, and sneezing. Sciatic nerve injury occurs between 0.5% and 2.0% of the time during a hip replacement. Sciatic nerve palsy is a complication of total hip arthroplasty with an incidence of 0.2% to 2.8% of the time, or with an