What are the hip flexor muscles?

Hip flexors are the muscle that allows your knee to be raised up to your chest. Ways to strengthen these muscles include walking and swimming.

Located at the lower portion of the spine and top of the hip, hip flexor muscles insert into the upper middle portion of the thigh (femur). They help bend (flex) the hip and rotate the thigh externally.

The hip flexors are a group of skeletal muscles that act to flex the femur (thigh bone) onto the lumbo-pelvic complex, i.e., pull the knee upward.

The hip flexors are (in descending order of importance to the action of flexing the hip joint):[1]

Collectively known as the iliopsoas or inner hip muscles:

• Psoas major
• Psoas minor
• Iliacus muscle

• Rectus femoris (part of the quadriceps muscle group)
• Sartorius

One of the gluteal muscles:

Tensor fasciae latae

Medial compartment of thigh

• Pectineus
• Adductor longus
• Adductor brevis
• Gracilis

Without the iliopsoas muscles, flexion in sitting position is not possible across the horizontal plane.

The tensor fascia lata (TFL), quadriceps, and sartorius muscles comprise what I call the big three hip flexors. These muscles are often overlooked in rehabilitation with more focus placed on a fourth hip flexor, the iliopsoas. In my opinion, though, these three hip flexors cause much more damage due to their size, the fact that they alter pelvic and knee mechanics, and their involvement in just about everything we do with our legs.