The thigh is the part of the lower limb located between the hip and the knee, and it can be divided into anterior, medial and posterior compartments that surround the femur. These compartments are formed by the intermuscular septa that originate on the inner surface of the fascia lata and attach to the linea aspera of the femur.
And, more importantly, each compartment contains its own muscles, as well as blood vessels and nerves. Each muscle in the three compartments has a proximal origin and distal insertion, a neurovascular supply, and a specific action on the joints of the lower limb.
So, the anterior compartment, which is the largest one, includes the anterior thigh muscles, which can function as flexors of the hip and extensors of the knee. First, the flexors of the hip include the pectineus, iliopsoas, and sartorius.
The pectineus is an almost rectangular muscle located in the anterior part of the superomedial portion of the thigh, and it’s often composed of a superficial and deep layer. It originates on the superior ramus of the pubis and inserts on the pectineal line of the femur, just inferior to the lesser trochanter.
Now, this muscle has a lot of nerve, mainly because of its dual nerve supply. One supply is from the femoral nerve, and the second supply is from a branch of the obturator nerve. Finally, the pectineus has 3 main actions - it adducts, flexes, and medially rotates the thigh. This is one muscle, two nerves, and three actions!
Second, the iliopsoas is the most powerful of the hip flexors. It has most of its mass located in the posterior wall of the abdomen and greater pelvis. Actually, it consists of two parts. Its broad lateral part is called the iliacus muscle, which arises from the floor of the iliac fossa, ala of the sacrum, inner lip of the iliac crest, and anterior sacroiliac ligaments.
