A 24-year-old man had a history of blunt trauma to his left leg while playing cricket one year back. He complained of a painless swelling over the anterior aspect of the leg after a few months. It increased in size on standing and during muscle contraction.
Ultrasound of the left leg showed a 6mm defect in the echogenic fascia overlying the tibialis anterior muscle (Figure 1). On dynamic examination (Figures 2 and 4/video), there was herniation of the muscle fibres through the myofascial defect on standing and forced dorsiflexion of the foot. It is reduced in the supine position with muscle relaxation and on graded compression. An MRI (magnetic resonance imaging) of the left leg showed a defect in the fascia with bulging of the fibres of the tibialis anterior (Figure 3). There was no abnormal signal intensity in the muscle.
Muscle herniation is an entity where there is a defect in the overlying fascia with resultant herniation of muscle fibres through it. It is commonly seen in young individuals such as athletes, military soldiers, and mountain climbers [1]. The aetiology could be either congenital or acquired. A congenital defect in the fascia or perforation by a vessel or nerve serve as potential sites for muscle herniation [2,3]. Acquired causes are usually traumatic, which might be due to direct trauma or due to excess use of the muscle. Iatrogenic muscle hernia is seen after harvesting flaps for reconstruction surgeries [1]. Regular physical activity with muscle hypertrophy is a risk factor. Muscle herniation is commonly seen in the leg and rarely in the thigh and the upper extremities. The most commonly involved muscle is the tibialis anterior. It is also seen in the peroneus longus and brevis, the extensor and flexor digitorum longus, the gastrocnemius and in the rectus femoris [1,3].
The diagnosis of muscle hernia requires a high index of clinical suspicion. The swelling is usually painless and is prominent on muscle contraction and standing. Pain might be due to muscle oedema. Ultrasonography is the initial mode of investigation, which clinches the diagnosis and also rules out common mimics. The additional benefit is the use of dynamic examination with muscle contraction and in standing position. The fascia appears as a thin echogenic line over the muscle. The defect is appreciated on muscle contraction. On relaxation, there might be focal thinning of the fascia with slight elevation, which can be missed easily [4]. A defect is not necessarily seen in every case [5]. The clue to the diagnosis is a focal bulge with thinning of the fascia at the site of the swelling. The mushroom-like (convex superficial contour of the muscle with a narrow defect) and the spoke-like appearance (pinching effect on the echogenic adipose septae at the site of the fascial defect) have been described on ultrasound. The herniated muscle is usually hypoechoic to the normal adjacent muscle [1]. An MRI confirms the diagnosis by depicting the fascial defect. T2/PDFS hyperintensity within the herniated muscle suggests muscle oedema. Dynamic examination with fast imaging makes the defect more conspicuous [5].
Muscle hernias are usually managed conservatively with rest and stocking support [3]. Surgical management is done through fasciotomy [1]. Defect repair is not preferred due to the risk of compartment syndrome [1].
Tibialis anterior muscle hernia
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The patient is a 24-year-old male presenting with a protruding mass on the anterior aspect of the left lower leg. Ultrasound examination shows a localized defect in the fascia of the tibialis anterior muscle. When the muscle contracts or the patient stands bearing weight, the muscle tissue bulges through the fascial defect, creating a visible “protrusion.” On ultrasound, there is a discontinuity in the superficial fascial band, with muscle fibers protruding through and showing mild compression. MRI also reveals a localized defect in the same region of the fascia, and the protruding muscle fibers demonstrate high signal edema on T2 sequences, suggesting minor injury and exudation due to mechanical stress at that site.
Taking into account the patient’s age, any history of trauma, the painless local bulge, and the consistent ultrasound and MRI findings of fascial defect and muscle protrusion, the most likely diagnosis is a muscle hernia in the tibialis anterior region of the left lower leg. If the clinical presentation is atypical or further confirmation is needed, dynamic ultrasound (during compression and contraction) or rapid-sequence MRI can be performed to confirm the presence of a genuine fascial defect or to rule out other pathologies.
Treatment Strategies:
1. Conservative Treatment: For patients with mild symptoms and no obvious functional impairment, external support such as elastic bandages or compression sleeves can be used to reduce excessive muscle protrusion during contraction. Adequate rest and avoiding excessive exercise are also recommended.
2. Surgical Treatment: This is considered only in cases of recurrent episodes, significant pain, or impact on athletic performance. The usual approach involves fascial repair or reconstruction. However, caution regarding compartment syndrome and other complications is necessary. According to some literature, certain experts opt for decompression alone without complete fascial suturing to avoid increased compartment pressure.
Rehabilitation/Exercise Prescription (FITT-VP Principle):
1. Type of Exercise: Start with low-impact activities (swimming, stationary cycling) and gradually reintroduce weight-bearing exercises (e.g., brisk walking, light jogging). Avoid high-intensity or excessive twisting movements.
2. Frequency: Begin with 2-3 sessions per week, allowing sufficient rest and muscle recovery, and gradually increase to 3-5 sessions per week.
3. Intensity: Train at a “moderate intensity,” meaning the individual feels some exertion but not excessive fatigue. Increase gradually according to tolerance.
4. Time: Start with approximately 20 minutes per session and progressively increase to 30-45 minutes, depending on individual tolerance.
5. Progression of Exercise: If the patient tolerates low-intensity activities well, gradually introduce mild strength training (targeting the calves, quadriceps, etc.) to improve local muscle strength and stability.
6. Volume Control: Monitor for signs of local swelling, pain, or other discomfort. If these occur, decrease the exercise volume or pause as necessary.
7. Safety Precautions: During exercise, if pain worsens, the bulge increases in size, or other discomfort arises, stop training and seek medical evaluation.
This report is based on the current clinical and imaging data provided. It is for reference in medical decision-making and does not replace in-person consultations or advice from professional physicians. Specific treatment plans should be determined by a specialist based on the patient’s actual condition.
Tibialis anterior muscle hernia
