Now let’s move on, and look at the three muscles which produce abduction at the hip joint. The two important abductors are gluteus minimus, and gluteus medius. We’ll go round to the back to look at them.
Here are the short rotator muscles that we’ve seen already, quadratus femoris, obturator internus and the gemelli, and piriformis. Now we’ll add
gluteus minimus to the picture. Gluteus minimus arises from this part of the wing of the ilium. It’s inserted here, on the front of the greater trochanter.
Overlying gluteus minimus, is gluteus medius. Gluteus medius arises
from this part of the ilium. It’s inserted here, on the outer aspect of the greater trochanter.
Though gluteus medius is mainly an abductor as we’ll see, its anterior part also produces medial rotation at the hip.
The last of the abductors is called the tensor fascia lata. Before we look at it, we need to digress for a minute, and get acquainted with the structure that gives it its name, the fascia lata.
The fascia lata is a continuous sheet of dense fibrous tissue that surrounds all the muscles of the thigh. Along the outer aspect of the thigh there’s a very marked thickening of the fascia lata called the ilio-tibial tract. The ilio-tibial tract extends all the way from here on the ilium, down to here, on the tibia.
Here’s the ilio-tibial tract by itself, with the rest of the fascia lata removed. These muscles, in front of it and behind it, we’ll be looking at in a minute. Between the muscles is a strong fibrous septum, which attaches the ilio-tibial tract to the femur. At its lower end, the ilio-tibial tract is attached down here on the tibia.
The ilio-tibial tract acts as the tendon of insertion of two muscles, a big one back here, gluteus maximus, which we’ll see later, and this one, which we were just getting ready to look at, tensor fascia lata.
Tensor fascia lata arises from the iliac crest here. It inserts here on the ilio-tibial tract.
The three hip abductors move the limb to the side. When the foot is on the ground the hip abductors, pulling down on the ilium, raise the opposite side of the pelvis up. This tilting of the pelvis happens in a small way each time we take a step, making it easy for the opposite foot to move forward without touching the ground.