Iliopsoas

The Iliopsoas is sometimes classified as two muscles, Iliacus and Psoas major, with Iliacus arising from the Ilium and Psoas from the vertebrae.

Action:
Flexes and laterally rotates hip as well as flexing the  torso when the legs are fixed (e.g. laying to sitting).

Typical use:
•    Climbing a step.

Sartorius

The Sartorius is a two joint muscle and so is weak when the knee is flexed and the hip is flexed at the same time. It works better during single movements.

Action:
Flexes, abducts, laterally rotates thigh at hip. Flexes, medially rotates leg at knee. Abducts the hip and externally rotates the hip as it flexes the hip and knee.

Typical use:
•    Sitting in a cross-legged position.

Rectus Femoris

The Rectus Femoris muscle is part of the Quadriceps muscle group.

It is the only muscle of the group which crosses the hip joint and is a powerful knee extensor when the hip is extended, but is weak when the hip is flexed.

Action:
Extends leg at knee. Flexes thigh at hip.

Typical use:
•    Kicking a football.

Gluteus Medius

The Gluteus Medius is an important muscle in controlling the level of the hips.

Weaknesses in gluteus medius often result in a trendelenburg sign, an abnormal gait cycle where the hip of the swinging leg drops down, rather than raises up.

This results in increased degrees of knee flexion in order to clear the ground.

Action:
Abducts and medially rotates hip. Tilts pelvis on walking.
The posterior fibres externally rotate the hip.
The anterior fibres internally rotate the hip.

Typical use:
•    Stepping sideways out of the bath.

Gluteus Minimus

This is the smallest of the three gluteal muscles and sits underneath the gluteus medius.

Action:
Abducts and medially rotates hip. Tilts pelvis on walking.

Typical use:
•    Getting out of a car.

Gluteus Maximus

The Gluteus Maximus is the largest and most superficial of the three gluteal muscles which forms the rounded shape of the buttocks.

Action:
Extends and laterally rotates hip and keeps the knee extended via iliotibial tract

Typical use:
•    Extension phase of walking upstairs.

Piriformis

The Piriformis muscle is an important muscle. The sciatic nerve passes underneath this muscle on its route down to the posterior thigh.

In some individuals the nerve can actually pass right through the muscle. This can lead to sciatica symptoms due to a condition known as piriformis syndrome

Action:
Laterally rotates, abducts and stabilises the hip.

Typical use:
•    Taking the first leg out of the car.

Biceps Femoris

The Biceps Femoris is one of the three muscles which form the hamstring group forming the back of the thigh.

The muscle is often described as having a long head (the attachment from the ischium) and a short head (attached to the femur).

Action:
Flexes and laterally rotates knee and laterally rotates the hip when the knee is flexed. The long head extends hip.

Typical use:
•    Bending the knee to step over something.

Semitendinosus

When running the hamstrings act eccentrically to slow down the knee extension motion.

Hamstring strains are common in individuals with chronically tight hamstrings or who do not warm-up thoroughly.

Action:
Flexes and medially rotates knee, and extends the hip.

Typical use:
•    Bending the knee to step over something.

Semimembranosus

The Semimembranosus is the most medial of the three hamstring muscles.

Chronically tight hamstrings are often a contributary factor to lower back pain and knee pain.

Action:
Flexes and medially rotates knee, and extendsthe  hip.

Typical use:
•    Bending the knee to step over something.

Pectineus

The Pectineus is positioned between the Iliopsoas and Adductor Longus muscles and is part of the short adductor group with adductors brevis and longus.

Action:
Flexes, adducts and medially rotates the hip.

Typical use:
•    Kicking a football.

Adductor Brevis

The Adductor Brevis is the smallest and shortest (hence the name brevis, meaning short in latin) of the three short adductor muscles.

Groin strains are common injuries to the adductor muscles, which occur without a thorough warm-up or in individuals with chronically tight or weak adductor muscles.

Action:
Adducts and flexes the hip.

Typical use:
•    Bringing your second leg into the car.

Adductor Longus

The Adductor Longus is the middle of the three short adductor muscles.

Groin strains are common injuries to the adductor muscles, which occur without a thorough warm-up or in individuals with chronically tight or weak adductor muscles.

Action:

Adducts, flexes and medially rotates hip.

Typical use:
•    Bringing your second leg into the car.

Adductor Magnus

The Adductor Magnus is the largest groin muscle and is one of the two long adductor muscles (gracilis is the other).

It is usually decribed as having two parts, hamstring and adductor parts.

Action:
Adductor portion: adducts, flexes and medially rotates hip. Hamstring portion: extends hip.

Typical use:
•    Bringing your second leg into the car.

Gracilis

The Gracilis is another muscle which works in conjunction with the groin muscles, or adductors.

Action:
Adducts hip. Flexes knee and medially rotates the hip when the knee is flexed.

Typical use:
•    Sitting with the knees pressed together.