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The greater trochanter is an irregularly shaped bony feature at the top of the femur bone in the thigh. Situated just below and to the outside of the hip joint on the outer aspect of the femur, it is a rough and convex section of the bone that is found alongside the neck of the femur. The function of the greater trochanter is to act as a site of insertion for several muscles of the posterior hip and a site of origin for a muscle of the anterior thigh, the vastus lateralis.
At the very top of the femur bone, the large, angled bone of the thigh, is a ball-shaped head, which angles inward and upward to insert into the hip socket, forming the acetabulofemoral joint. Projecting outward and downward from the head of the femur is the neck, which then curves downward and slightly inward to form the body of the femur. The greater trochanter is found just alongside the neck of the femur toward the lateral and posterior aspect of the bone, just beyond where the femur exits the hip joint. It can be seen as raised, rough, diagonal surface stretching upward and outward, forming an apex just lateral to and slightly below the head of the femur.
A large number of muscles in the posterior hip attach via tendons to the greater trochanter. These include the gluteals, the piriformis, the obturator internus, and the gemelli, muscles that collectively are responsible for extension, abduction, or lifting the leg sideways, and rotation of the thigh in the hip joint. The gluteus medius and minimus, smaller gluteal muscles found along the upper, outer buttocks, both insert along the superior or top aspect of the trochanter, with the tendon of the minimus attaching in front of that of the medius. Below the gluteals on the back of the hip is the piriformis, which externally rotates and abducts the thigh and which inserts on the medial surface of the trochanter, just to the inside of the tendons of the gluteals.
Beneath the piriformis are the superior gemellus, obturator internus, and inferior gemellus, smaller muscles that externally rotate and abduct the thigh. The gemelli muscles attach to the horizontal tendon of the obturator from above and below. This tendon inserts on the medial aspect of the greater trochanter below that of the piriformis.
The final muscle that attaches to the greater trochanter comes not from the posterior hip but the anterior thigh, and it does not insert to the trochanter but rather originates here. Arising from the ridged inferior or lower border of the trochanter is the vastus lateralis, an extensor of the knee joint. One of four muscles of the quadriceps, the vastus lateralis originates via a tendon below those of the attaching hip muscles and curves around the outside of the femur to run down the front of the thigh.
I'm wondering if the greater trochanter limits abduction of the femur by maybe pressing into the side of the hip or soft tissue there? And if this is why when the femur externally rotates before abducting that the angle of abduction is greater because the greater trochanter has been moved out of the way?