A hip flexor strain is an injury characterized by over stretching or tearing of one or more of the hip flexor muscles, and typically causes pain in the front of the hip or groin; the groups of muscles at the front of the hip are called the hip flexors. The most commonly involved muscle(s) in a hip flexor strain are the iliopsoas and illiacus. aThe iliopsoas muscle originates from the lower back and pelvis and inserts into the thigh bone (femur).The illiacus originates from the pelvis and inserts into the thigh bone as well.

The hip flexors are responsible for moving the knee towards the chest (i.e. bending the hip) during activity and are particularly active when sprinting or kicking. Whenever the hip flexors contract or are put under stretch, tension is placed through the hip flexor muscle fibers. When this tension is excessive due to too much repetition or high force, the hip flexor muscle fibers may tear. When this occurs, the condition is known as a hip flexor strain.

Hip flexor strains generally occur due to a sudden contraction of the hip flexor muscles (particularly in a position of stretch). They often occur during sprinting or kicking activities. Patients may also develop this condition gradually due to repetitive or prolonged strain on the hip. The hip flexors may also become shortened due to prolonged sitting postures, resulting in painful trigger points and developing a lower crossed syndrome. (Many people who have chronic low back pain that does not respond to therapy have tight and shortened hip flexor muscles).

Patients with acute injury usually feel a sudden sharp pain or pulling sensation in the front of the hip or groin: however, the pain of chronic hip strain is a dull ache in the thigh or groin, and or the low back. (chronic unresponsive low back pain may result from hip flexor injury).Patients with this condition usually experience pain when lifting the knee towards the chest (especially against resistance) or during activities such as running, kicking or going upstairs. It is also common for patients to experience pain or stiffness after rest, especially upon waking in the morning. Swelling, tenderness and bruising may also be present in the hip flexor muscles

Most patients with this condition will heal with appropriate therapy. The success rate of treatment is largely dictated by patient compliance. One of the key components is that the patient rests from any activity that increases their pain until they are symptom free. Activities which place large amounts of stress through the hip flexors should be minimized, particularly running and kicking activities. Rest from aggravating activities ensures the body can begin the healing process in the absence of further tissue damage. If not treated properly the condition can become chronic, and healing slows significantly resulting in markedly increased recovery times and an increased likelihood of future recurrence.

There are several factors which can predispose patients to developing this condition. Some of these factors include:

– muscle weakness (particularly of the quadriceps, hip flexors or gluteals)
– muscle tightness (particularly of the hip flexors, quadriceps, hamstrings or gluteals)
– inappropriate training
– inadequate warm up
– joint stiffness (especially the lower back, hip or knee)
– poor biomechanics
– poor posture
– inadequate rehabilitation following a previous hip flexor injury
– decreased fitness
– fatigue
– poor pelvic and core stability
– neural tightness
– muscle imbalances

Treatment for hip flexor strain consists of:

– soft tissue massage
– Trigger point therapy
– electrotherapy (e.g. ultrasound, electrical stimulation)
– joint mobilization (especially the lower back and hip)
– stretches
– ice or heat treatment
– progressive exercises to improve strength and flexibility (particularly of the hip flexors)
– education
– biomechanical correction
– activity modification advice
– establishment of an appropriate return to activity or sport plan