The list of muscles that flex the hip is long. Some of these muscles are single joint while some are 2-joint muscles flexing the hip and extending or flexing the knee.
The main hip flexors are the Iliacus and Psoas, collectively known as the Iliopsoas. Iliacus originates from the iliac fossa and AIIS (Anterior Inferior Iliac Spine). The iliacus originates from the transverse processes of lumbar and last thoracic vertebra. Both these combine to form a common tendon of insertion on the lesser trochanter of femur.
There are several muscles that cross both the hip and knee like the Sartorius, Rectus Femoris, Tensor Fascia Lata via the IT band. The Pectineus, Adductor Longus and Adductor Brevis are single joint muscles in the medial compartment of the thigh which also serve as secondary hip flexors (primary function of these muscles is adduction) with the thigh turned outwards. The Gracilis also in medial compartment is a two-joint muscle flexing both the hip and the knee.
For purpose of stretch, we will focus on the main hip flexors- the iliacus and psoas. Since the Sartorius and Rectus Femoris are also in the anterior thigh compartment, they are stretched to some extent also.
The various ways to stretch the hip flexors are:
In supine lying position on the mat, both legs are extended in neutral position. The physical therapist then flexes the left hip/knee completely to bring the knee to the stomach/chest, while the right leg is held straight with the back of thigh, knee, and leg resting on the mat (the right leg should not be allowed to bend/flex at hip and knee). Another thing to watch out for is an increased lumbar lordosis, which also indicates tight hip flexors. The key to stretch here is a posterior pelvic tilt with flattening of lumbar spine, thus pulling the proximal psoas, iliacus, Sartorius and rectus femoris fibers away from its distal insertion on femur or tibia, thus stretching it over the hip joint.
Active Static Stretch:
i) In supine lying on edge of the mat with the legs dangling over the edge at the knee joints. Place a chair at end of mat with feet supported on chair to maintain neutral spine posture, then engage the abdominals to tilt the pelvis posteriorly as the left hip/knee is held in complete knee-to-stomach/chest position by circling the arms around the left knee. The left hip/knee flexion ensures posterior pelvic tilt. Next, push the chair away from under the right foot and dangle the leg off the edge of mat, flexing the knee if possible. This stretches the iliacus, psoas and the rectus femoris and to some extent the Sartorius muscle.
ii) To stretch Sartorius, prone lying is best position. Here you have to watch for the lumbar spine, since when hip flexors are tight, they tend to pull the pelvis into anterior tilt/rotation and hence cause the lumbar spine lordosis to increase. So always be mindful of the lumbar spine position and keep the transverse abdominus engaged. Next, flex the right knee and turn the thigh to point inwards or drop the ankle out (hip medial rotation) and also slide the thigh inwards to the midline (hip adduction). Now slowly drop the foot to mat by extending the right knee. Hold if stretch is felt, if not, lift thigh off the mat by extending the hip. You may place a pillow under the knee to hold hip in extension and then slowly extend the knee. Watch for the lumbar spine though, ensuring extension at hip (10°-15° only) and not increased lordosis at the lumbar spine. There are lots of elements in this stretch to get it correctly.
Active Dynamic Stretch:
There are several yoga asanas that stretch the hip flexors. These asanas entail nuances in muscle control and to be done correctly should be done in presence of trained instructor and practiced solo after learning them initially. Since they involve back extension which narrows the foraminal space, they are contraindicated in certain conditions like back ache and neck pain and digestive disorders.
i) The Anjaneya asana: You basically start in half-kneeling position with the left foot on the floor in front and the right leg resting on the knee and ball of foot, behind. Slide the right knee back as far as possible and lunge forward on the left foot by shifting the body weight forward and arching the lumbar spine forward with arms outstretched overhead to keep spine elongated. This stretches the front of the right hip, thigh, and anterior spine to effectively stretch the psoas and iliacus. When the right knee is flexed, and resting on the ground, it stretches the rectus femoris, and when the right knee is extended lifting it off the ground in lunge position, it stretches the Sartorius at the knee joint as well. Hold pose for 2-3 breath cycles and release by first bringing right knee to floor, engaging abdominals to bring spine to neutral and then shifting body weight to come out of lunge position.
ii) Dhanurasana or the bow pose: This is done in prone position, lying on the stomach with arms by the side of trunk, palms facing upwards. Bend both the knees bringing the feet to buttocks and hold the feet around the ankles with your hands. As you inhale, lift the heels away from butttocks and lift the thigh off the floor as the torso lifts up. Ensure both knees are no more than hip width apart. Hold for 2-3 breath cycles and release by first lowering the thighs and torso while bending the knees. Lastly release the hand-hold around the ankles and extend knees.
iii) Ustrasana or camel pose: This asana is intermediate to advanced level and should be done in presence of trained instructor. Begin in kneeling position on the mat with knees hip width apart and dorsum of foot resting on the floor. Place both the hands around the waist, thumb in front and fingers around the back. Gently tilt pelvis back by engaging the abdominals and elongate the lumbar spine. Inhale and lift the sternum (breast bone) upwards. Bring the knee and elbow joints closer together by internally rotating hips and externally rotating shoulders. Stay here for 2-3 breath cycles and slowly slide hands down the back, by extending elbow joints, to the heels of feet. Open the shoulders without squeezing the shoulder blades (releasing the pectorals) and extend the neck by eccentric contraction of neck flexors for slow controlled movement.
Stretches with tools and equipment:
i) Standing hip flexor stretch with rolling stool or chair: Stand facing a wall with hands stretched forward and palms resting on the wall for support. The rolling stool or chair should be pre-adjusted to knee height. Bend the right knee by lifting foot back and up from the floor till knee is flexed at 90 degrees. Rest the knee on the seat of the stool/chair (chair should be forward facing to allow leg to be supported on chair). Left foot is on the floor and both hands are on wall forming a three-point support base. Engage the abdominals to ensure lumbar spine remains in neutral throughout stretch. Slowly roll the stool/chair back with the right leg by extending the hip joint (not lumbar spine- you are doing this if lumbar arch or lordosis increases). Hip joint has about 10-15 degrees of extension range, so move back slowly to avoid lumbar extension. Hold position for as long as you can, for 5-30 seconds, once you feel stretch in groin area. Release and repeat 2-3 times with 15-30 second rest breaks in between stretches.
ii) Half-kneeling with Airex-pad: Begin in half-kneeling position with left foot on floor and right knee on the Airex-pad for cushioning under knee/shin. Engage abdominals to keep neutral pelvis and lumbar spine. Lunge forward on left leg by flexing hip and knee as the right knee stays put on the airex pad slowly and passively bringing extension at right hip joint, thus stretching the single joint hip flexors. Hold position as long as possible from 5-30 seconds, release, and repeat 2-3 times with 15-30 second rest break in between stretches.
Ami Gandhi is a licensed physical therapist in the state of California. She is the owner of StableMovement Physical Therapy, a small boutique practice in San Jose that offers patient centered, one-on-one, hands-on physical therapy.