The thigh muscles don’t just move your legs. They have a lot to do with how your hips move. In clinical anatomy the thigh muscles are divided into three groups: Anterior muscles extend your legs and flex your thighs. Medial muscles adduct and rotate your thigh, and posterior flex your leg and extend your thigh.
THE ANTERIOR THIGH MUSCLES
The muscles of the anterior part of the thigh include the quadriceps group and a few others:
Quadriceps femoris: This muscle includes four heads that originate in different locations but all share the quadriceps tendon, which inserts onto the patella. The continuation of the quadriceps tendon that extends from the patella and inserts onto the tibial tuberosity of the tibia is called the patellar ligament. All four parts of the muscle are innervated by the femoral nerve, and they extend the knee. The rectus femoris, however, also flexes the hip.
Sartorius: Originating on the anterior superior iliac spine, this muscle inserts on the medial surface of the tibia. It’s innervated by the femoral nerve, and it flexes, abducts, and laterally rotates the thigh. It also flexes the leg at the knee.
Iliopsoas: The iliopsoas is made up of two muscles that flex the thigh. One of those muscles, the psoas major, is also important for posture:
THE MEDIAL THIGH MUSCLES
The muscles of the medial part of the thigh include muscles that bring the thigh toward the midline and rotate it:
Adductor longus: This muscle originates on the pubis and inserts onto the middle of the linea aspera of the femur. It’s innervated by the obturator nerve and adducts the thigh.
Adductor brevis: Originating on the pubis and inserting on the pectineal line and linea aspera of the femur, this muscle is innervated by the obturator nerve. It adducts the thigh.
Adductor magnus: This muscle originates on the pubis and the ischial tuberosity. It inserts onto the gluteal tuberosity, linea aspera, and the adductor tubercle of the femur. It’s innervated by the obturator nerve and the sciatic nerve. It adducts the thigh and assists in both flexion and extension of the thigh.
Gracilis: This muscle originates on the pubis and inserts on the medial tibia. It’s innervated by the obturator nerve. It adducts the thigh and flexes the leg at the knee.
Obturator externus: Originating at the obturator foramen and membrane of the hip bone, this muscle inserts onto the femur. It’s innervated by the obturator nerve and laterally rotates the thigh
THE POSTERIOR THIGH MUSCLES
The three muscles of the posterior thigh are known as the hamstring muscles. They extend the thigh from a flexed position and flex the leg.
Semimembranosus: The most medial of the three hamstring muscles, this muscle originates on the ischial tuberosity and inserts on the medial condyle of the tibia. It functions with the semitendinosus to extend the thigh and flex and medially rotate the leg. It’s innervated by the tibial portion of the sciatic nerve.
Semitendinosus: This muscle originates on the ischial tuberosity and inserts onto the superior part of the medial tibia. It’s innervated by the tibial portion of the sciatic nerve and extends the thigh and flexes and medially rotates the leg.
Biceps femoris: The most lateral of the hamstrings, the biceps femoris has two heads: the long and the short. The long head originates on the ischial tuberosity, and the short head originates on the linea aspera of the femur. They insert onto the lateral side of the fibula. The long head is innervated by the tibial portion of the sciatic nerve, and the short head is innervated by the fibular portion of the sciatic nerve. It extends the thigh and flexes and laterally rotates the leg.
THE ANTERIOR THIGH MUSCLES
The muscles of the anterior part of the thigh include the quadriceps group and a few others:
Quadriceps femoris: This muscle includes four heads that originate in different locations but all share the quadriceps tendon, which inserts onto the patella. The continuation of the quadriceps tendon that extends from the patella and inserts onto the tibial tuberosity of the tibia is called the patellar ligament. All four parts of the muscle are innervated by the femoral nerve, and they extend the knee. The rectus femoris, however, also flexes the hip.
- Rectus femoris forms the middle portion of the quadriceps. It originates at the anterior inferior iliac spine and just above the acetabulum of the hip bone.
- Vastus lateralis is the lateral-most head. It originates at the greater trochanter and the linea aspera of the femur.
- Vastus medialis is the most medial of the heads. It originates on the intertrochanteric line and linea aspera.
- Vastus intermedius lies behind the rectus femoris. It originates on the shaft of the femur.
Sartorius: Originating on the anterior superior iliac spine, this muscle inserts on the medial surface of the tibia. It’s innervated by the femoral nerve, and it flexes, abducts, and laterally rotates the thigh. It also flexes the leg at the knee.
Iliopsoas: The iliopsoas is made up of two muscles that flex the thigh. One of those muscles, the psoas major, is also important for posture:
- Psoas major originates on the 12th thoracic and the five lumbar vertebrae. It inserts onto the lesser trochanter of the femur and is innervated by the first three lumbar spinal nerves.
- Iliacus originates on the iliac crest, sacrum, and sacroiliac ligaments. It inserts onto the tendons of the psoas major and the lesser trochanter of the femur. It’s innervated by the femoral nerve.
THE MEDIAL THIGH MUSCLES
The muscles of the medial part of the thigh include muscles that bring the thigh toward the midline and rotate it:
Adductor longus: This muscle originates on the pubis and inserts onto the middle of the linea aspera of the femur. It’s innervated by the obturator nerve and adducts the thigh.
Adductor brevis: Originating on the pubis and inserting on the pectineal line and linea aspera of the femur, this muscle is innervated by the obturator nerve. It adducts the thigh.
Adductor magnus: This muscle originates on the pubis and the ischial tuberosity. It inserts onto the gluteal tuberosity, linea aspera, and the adductor tubercle of the femur. It’s innervated by the obturator nerve and the sciatic nerve. It adducts the thigh and assists in both flexion and extension of the thigh.
Gracilis: This muscle originates on the pubis and inserts on the medial tibia. It’s innervated by the obturator nerve. It adducts the thigh and flexes the leg at the knee.
Obturator externus: Originating at the obturator foramen and membrane of the hip bone, this muscle inserts onto the femur. It’s innervated by the obturator nerve and laterally rotates the thigh
THE POSTERIOR THIGH MUSCLES
The three muscles of the posterior thigh are known as the hamstring muscles. They extend the thigh from a flexed position and flex the leg.
Semimembranosus: The most medial of the three hamstring muscles, this muscle originates on the ischial tuberosity and inserts on the medial condyle of the tibia. It functions with the semitendinosus to extend the thigh and flex and medially rotate the leg. It’s innervated by the tibial portion of the sciatic nerve.
Semitendinosus: This muscle originates on the ischial tuberosity and inserts onto the superior part of the medial tibia. It’s innervated by the tibial portion of the sciatic nerve and extends the thigh and flexes and medially rotates the leg.
Biceps femoris: The most lateral of the hamstrings, the biceps femoris has two heads: the long and the short. The long head originates on the ischial tuberosity, and the short head originates on the linea aspera of the femur. They insert onto the lateral side of the fibula. The long head is innervated by the tibial portion of the sciatic nerve, and the short head is innervated by the fibular portion of the sciatic nerve. It extends the thigh and flexes and laterally rotates the leg.