The hips are a joint region also known as the “coxa” or acetabulofemoral joint and connects the femur and acetabulum. The acetabulum is the hip plate and is made up of the ischium, the ilium, and the pubis which are fused in adult humans. The hip-joint is the most important joint for dynamic movement, balance, and is possibly the most influential joint on posture.
The joint itself is called a synovial joint, because the head of the femur is rounded and the hip plate forms a socket that allows for massive amounts of articulation or movement. The greater trochanter (GT) is a protrusion at the upper-outer part of the femur bone where the piriformis originates. The more lateral, or outside portion of the GT is where the tendon of glutieus medius originates. The inside portion is filled with muscles that attach the GT to the hip plate, two obterator muscles, two gemellus muscles, the quadratus femoris, a portion of the adductor, and the inferior portion gives way to the vastus lateralis which connects to the top of the kneecap. The GT is often a bone that fails due to osteoporosis in old age.
The head of the femur, a round ball like insertion is connected to the socket of the hip, the acetabulum notch is connected via ligamentum teres, which travels through the fovea capitis, a hole in the bone. The notch is covered with the transverse acetabular ligament and capsular ligaments, which are closed with two strands of ligament called zona orbicularis.
The Pelvic girdle is formed with the iliac crest at the top or superior part of the Ilium which is the long, awkwardly shaped bone that slopes downwards. This structure extends down to form the acetabulum, the socket for the femur bone and the pubis on the inner-bottom portion of the hip and the ischium on the outer-bottom portion of the hip bone. The left and right pubis bones form together at the pubic synthesis and the Ischium is the bone that extends down in the back and forms the base of the part of the hip bone that we sit on, combined with sacrum and cocsys.
Blood Supply of the Hips
The femoral arteries supplies blood to the joint and descends down into the profunda femoral artery and the superficial femoral artery, as well as the lateral cicrumflex and medial circumflex arteries. The internal Iliac artery is the primary artery of the pelvis and has a significant artery that flows through the obturator canal. You can see how the veins descend down the leg on the image to the right, which shows how the arteries cascade down the leg and the femur bone, supplying the densest muscular region on the body.
Muscles of the Hips
The outer muscles of the hips are what allow for such powerful movement, and so far we’ve looked at the deepest layers of muscular tissue. The psoas muscles connect the five lumbar vertebrae to the lesser trochanter of the femur and run alongside the iliacus muscle from the hip crest to the lesser trochanter across the front of the hips. The tensor fascia latae runs along the lateral portion of the femur and the inner muscles of the thighs run from medial crest of the pubis bone to the inside of the femur. The adductor brevis, adductor longus, and adductor magnus form the main sheaths of muscle inside of the thigh. The gracilis runs superficially to all of the muscles and connects to the top of the Tibia to stabilize and adduct the entire leg. The pectineus muscle runs along the front inner thigh, from the front of the pubis to the back of the upper part of the femur. It is the most anterior hip adductor, though it mainly supports the hips in flexion. Finally, the piriformis runs from the greater trochanter to the sacrum at the back of the hip sits below the gluteus medius. All of these muscles sit anterior to the gluteus maximus, which covers the entire back of the hips and connects to the tensor fascia latae and the vastus lateralus.
The pelvic floor muscles, also known as the ‘mula bandha’ in yoga are the levator ani and coccygeus muscles, as well as fascia spanning the pelvic diaphragm. These can be further separated into individual muscles, but it will suffice to say that these muscles span the floor of the hips.
The Nerves of the Hips
There are three primary nerves that descend down the hips and into the leg. All of the nerves begin at the lumbosacral plexus in the Lumbar spine, L1-L4 and sacral plexus in the sacrum. These can be grouped together as the lumbrosacral plexus. The femoral nerve is the largest branch of this plexus and extends down the front of the leg, the Sciatic nerve extends down the back of the leg from the sacrum, and the lateral cutaneous nerve of the thigh, which crosses the top of the thigh. This is an extremely important pathway for the nervous system that controls movement and innervation in the lower body and the nerves can dysfunction.