Overview
The musculature of the thigh is divided into anterior, medial and posterior compartments, each with distinct innervation and function.
Iliopsoas
The iliopsoas is a large compound muscle of the inner hip, composed of the psoas major and the iliacus.
- Origins:
- Psoas major originates from the lumbar vertebrae
- Iliacus originates from the iliac fossa of the pelvis
- Insertion: Common tendon inserts on the lesser trochanter of the femur
- Actions: Flexes the thigh at the hip joint. (Unlike many of the anterior thigh muscles, the iliopsoas does not extend the leg at the knee joint)
- Innervation:
- Psoas major innervated by anterior rami of L1-3
- Iliacus innervated by femoral nerve (L2, L3, L4), branch of the lumbar plexus
Quadriceps Femoris
The quadriceps femoris consists of four individual muscles which collectively form the main bulk of the thigh and one of the most powerful muscles groups in the body. The muscles unite proximal to the knee and attach to the patella via the quadriceps tendon. In turn, the patella is attached to the tibia by the patella ligament. The quadriceps femoris is the main extensor of the knee.
Vastus Lateralis
- Origin: Originates from the greater trochanter and the lateral lip of linea aspera
- Actions: Extends the knee joint and stabilises the patella
- Innervation: Femoral nerve (L2, L3, L4), branch of the lumbar plexus
Vastus Intermedius
- Origin: Anterior and lateral surfaces of the femoral shaft
- Actions: Extends the knee joint and stabilises the patella
- Innervation: Femoral nerve (L2, L3, L4), branch of the lumbar plexus
Vastus Medialis
- Origin: The intertrochanteric line and medial lip of the linea aspera
- Actions: Extends the knee joint and stabilises the patella, particularly due to its horizontal fibres at the distal end.
- Innervation: Femoral nerve (L2, L3, L4), branch of the lumbar plexus
Rectus Femoris
- Attachments: Originates from the anterior inferior iliac spine and the area of the ilium immediately superior to the acetabulum. It runs straight down the leg and attaches to the patella via the quadriceps femoris tendon.
- Actions: The only muscle of the quadriceps to cross both the hip and knee joints. It flexes the thigh at the hip joint, and extends at the knee joint
- Innervation: Femoral nerve (L2, L3, L4), branch of the lumbar plexus
Sartorius
The sartorius is the longest muscle in the body. It is long and thin, running superficially across the other anterior thigh muscles in a inferomedial direction. The sartorius is positioned more superficially than the other muscles in the leg.
- Origin: Originates from the anterior superior iliac spin
- Insertion: Attaches to the superior, medial surface of the tibia
- Action: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor.
- Innervation: Femoral nerve (L2, L3, L4), branch of the lumbar plexus
Pectineus
The pectineus muscle is a flat muscle that forms the base of the femoral triangle
- Origin: It originates from the pectineal line on the anterior surface of the pelvis
- Insertion: Attaches to the pectineal line on the posterior side of the femur, just inferior to the lesser trochanter.
- Actions: Adduction and flexion at the hip joint.
- Innervation: Dual innervation
- Femoral nerve (L2, L3, L4), branch of the lumbar plexus
- May receive a branch from the obturator nerve (L2, L3, L4), branch of the lumbar plexus