Anatomy
The superficial hip flexor (the anterior rectus femoris muscle) originates from the front of the pelvis (spina iliaca anterior inferior, SIAI) and from the upper edge of the acetabulum. The muscle joins with 3 of the other thigh muscles and attaches to a common muscle tendon (quadriceps) on the upper edge of the kneecap. The function of the superficial hip flexor is to extend the knee and flex the hip.
Cause
When a muscle is subjected to repeated loads that exceed the muscle’s strength (jumping, kicking), damage to the muscle occurs most frequently at the tendon attachment. The repeated overloads can result in chronic ”Inflammation” and small tears that weaken the tissue and in the worst case result in a total rupture.
Symptoms
The pain is usually localised at the attachment of the SIAI on the front of the pelvis and may radiate down the front of the thigh along the muscle belly In mild cases, a localised soreness is felt at the start of exercise, but the symptoms can often fade after a thorough warm-up and return after the sporting activity has stopped (“muscle strain”, “threatening fibre”, “tendonitis”).
In more severe cases, a sudden shooting pain is felt in the muscle (“partial muscle rupture”, “fibre rupture”) and in the worst case, a violent pop is felt and it is impossible to use the muscle (“total muscle rupture”). In muscle injuries, the following three symptoms are characteristic: Pain when pressing, stretching and activating against resistance.
Examination
The diagnosis is usually made on clinical examination alone with localised pressure soreness on the muscle (often tendon attachment) with aggravation on stretching and muscle contraction. If the injury occurs suddenly with the sensation of a pop and reduced function of the muscle (flexion of the hip), a medical examination is advisable. In total tears, a defect in the muscle can often be seen and felt, and below the tear a swelling (the contracted muscle bulge and bleeding) is felt.
X-ray examination is indicated if there is a suspected tear of the piece of bone to which the muscle tendon attaches (SIAI). Ultrasound scanning will usually be able to assess the extent of the damage.
Treatment
Treatment primarily includes relief from pain-inducing activity, stretching and graduated rehabilitation within the pain threshold. Only in rare cases is surgery indicated (e.g. total rupture of the muscle tendon close to the attachment) (Choufani C, et al. 2022). Even large tears in the muscle tissue can usually be rehabilitated without functional damage (but often cosmetic with an irregular thigh muscle).
If no progress is made despite regular rehabilitation, rehabilitation may be supplemented with an injection of adrenal cortical hormone around the inflamed area at the muscle tendon attachment, followed by several months of rehabilitation to reduce the risk of recurrence and rupture.
Complications
If treatment does not go according to plan, you should consider whether the diagnosis is correct or if complications have arisen.
In particular, the following should be considered:
