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MRI Web Clinic - August 2023

Muscle Herniation

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Clinical History: A 13-year-old girl presents with a 10-day history of lateral left leg pain and a palpable mass which persisted after a period of prolonged walking.  The patient denies recent injury.  Physical exam revealed scar formation overlying the palpable abnormality at the site of a remote dog bite. Axial T1 (1a) and T2-weighted fat suppressed images (1b) are provided with coronal T1-weighted (1c) and STIR (1d) images.  What are the findings? What is your diagnosis?



Peroneus Longus Muscle herniation.


A muscle hernia occurs when the muscle protrudes through a defect in the deep peripheral fascia, the epimysium, into the subcutaneous fat.1 Ihde divided muscle hernias into post-traumatic and constitutional.2 Post-traumatic muscle hernias occur secondary to a penetrating injury, blunt trauma with contracted muscle, or surgery (Figure 3) that results in a fascial tear which permits herniation of the muscle into the subcutaneous fat.3,4 Constitutional muscle hernias occur due to vigorous exercise, muscle hypertrophy, and elevated intra-compartmental pressure with subsequent muscle herniation at points of fascial weakness, including sites at which the neurovascular bundle traverses the fascia.2,3,4,5,6 Constitutional muscle hernias with secondary nerve compression have been most frequently reported to affect the superficial peroneal nerve in the lower leg as it exits into the subcutaneous fat of the anterolateral aspect of the distal third of the leg (Figure 4).7,8,9

Muscle hernias most commonly occur in males, military members, athletes, and patients involved in strenuous activity, particularly heavy lifting.6,10 Patients typically present in the second to fourth decade of life.10 Muscle hernias are most prevalent in the middle and distal third of lower leg and may be multi-focal or bilateral, with hernias of the tibialis anterior most frequently encountered.4–6,11 Muscle hernias are less frequently encountered in the thigh and upper extremity (Figure 5). They have been theorized to cause pain due to contraction of the muscle against the proximal edge of the fascial defect, thus those occurring in the proximal muscle may lack adequate excursion required for compression against the proximal edge of the fascial defect.12

Clinical Presentation

Patients with muscle hernias most commonly present with a history of trauma and a palpable mass which may be asymptomatic or painful with exertion.4,12,13 On physical exam the mass is typically soft and reducible. The fascial defect can often be palpated.4,12,14  When the muscle is contracted the palpable abnormality may enlarge.11,14,15 The swelling may decrease with rest or, for those in the lower extremity, supine positioning.15 With constitutional hernias, occurring at sites where nerves traverse the fascia, patients may present with numbness, paresthesia, and/or hyperalgesia and have a positive Tinel’s sign on physical examination.7–9  


Appropriate imaging is critical to confirm and assess the extent of muscle injuries, exclude soft tissue masses and mimics, and help guide appropriate treatment.  In cases where there is an appropriate clinical history, physical exam, and high index of suspicion for muscle hernia, ultrasound is an appropriate initial imaging exam.11  In addition to a high accuracy in the assessment of muscle hernia it offers the advantage of dynamic imaging, including imaging muscle contraction or in an upright position, and at a lower cost and increased availability.3,11,14,16  A targeted ultrasound exam should be performed with a high frequency linear probe.  Both sides should be prepped for imaging as comparison with the contralateral side may increase diagnostic confidence in subtle cases.  At ultrasound the thin superficial layer of the deep fascia at the interface of the subcutaneous fat and muscle is visualized as a thin echogenic, bright, line superficial to the muscle.  A muscle hernia appears as a discontinuity in the echogenic fascia with muscle protruding into the defect (Figure 5).15 The muscle may be less echogenic than the adjacent non-herniated muscle.15 One pitfall to be mindful of when performing ultrasound is that excessive pressure with the ultrasound probe may reduce the hernia and result in a false negative exam.8,15

Click here to view video of figure 6D.

The excellent soft tissue contrast and high spatial resolution of MRI makes it well suited to evaluate muscle injury, muscle hernia, and the alternative differential considerations in the assessment of a soft tissue mass.  The diagnostic accuracy of MRI and US for evaluation of muscle hernia are comparable.11  MRI offers the advantage of better identifying which muscle is involved and characterizing any identified soft tissue mass.10  As with other small soft tissue masses, high resolution MR images should be acquired with a small field of view and thin sections with MRI compatible skin markers bracketing the palpable abnormality. At MRI muscle hernias appear as an abnormal bulge in the contour of the muscle or protrusion of the muscle into the subcutaneous fat.10,13,14  The T1 and T2 signal and architecture of the herniated muscle is usually normal, though increased T2 signal, indicative of edema, has been attributed to muscle tearing, impingement, or altered perfusion.10,16 A defect in the fascia is not always visualized, though it can be inferred from the abnormal muscle contour.11  Axial images typically better demonstrate the muscle hernia and fascial defect, while orthogonal images better characterize the longitudinal location and extent (Figure 2).10


The differential diagnosis for a palpable soft tissue mass is broad and varies by location.  In locations where muscle hernias are commonly encountered the primary differential considerations include post-traumatic foreign body (Figure 7), hematoma, and muscle tear; and neoplastic entities including lipoma (Figure 8) and nerve sheath tumor (Figure 9).8,17,18 In the forearm the differential includes congenital accessory muscles, which can mimic a muscle hernia both clinically and on imaging exams (Figure 10).12

Treatment and Prognosis

The treatment of muscle hernias is guided by the patient’s presenting symptoms.  In patients presenting with concern for soft tissue mass without focal pain, muscle hernias can be treated with reassurance.15,19 For patients with mild symptoms, including cramping, aching pain, and exertional discomfort the initial treatment is conservative with rest, activity modification, and support hose.10,19 In patients with moderate to severe pain, or for patients that fail conservative treatment, there are a variety of surgical options, with fasciotomy being the most widely accepted.5,12,19 Fasciotomy enlarges the fascial defect, allows unhindered muscle excursion, and eliminates the risk of future muscle ischemia or strangulation.6,8,12 Alternative surgical treatments include direct repair, muscle excision, fascial grafting, and mesh grafting.10,19  Direct repair is typically avoided in the lower leg due to the possibility of post-operative compartment syndrome.19,20 In a survey of athletes who underwent fasciotomy for symptomatic muscle hernia, Kramer et al. found that 82% of patients were satisfied with the results and 65% had returned to sports.5  


Muscle hernias are the uncommon result of a direct muscle injury which results in a fascial defect through which the underlying muscle can herniate.  Patients with muscle hernia most frequently present with a palpable soft tissue mass which may be reducible on physical exam. Imaging is essential to assess the extent of muscle injury and to exclude other causes of a palpable soft tissue masses.  On MR imaging, careful assessment of the muscle contour and the thin superficial fascia at the site of a palpable abnormality are essential for diagnosis. The most commonly accepted treatment for patients with severe or persistent pain attributed to muscle hernias is fasciotomy with extension of the fascial defect allowing unhindered muscle excursion and preventing muscle ischemia.    


  1. Kirchgesner T, Tamigneaux C, Acid S, et al. Fasciae of the musculoskeletal system: MRI findings in trauma, infection and neoplastic diseases. Insights Imaging. 2019;10(1):47. doi:10.1186/s13244-019-0735-5
  2. Ihde H. On muscular hernia of the leg. Acta Chir Scand . 1929;65:97-120.
  3. Kendi TK, Altinok D, Erdal HH, Kara S. Imaging in the diagnosis of symptomatic forearm muscle herniation. Skeletal Radiol. 2003;32(6):364-366. doi:10.1007/s00256-002-0615-8
  4. Zeiss J, Ebraheim NA, Woldenberg LS. Magnetic resonance imaging in the diagnosis of anterior tibialis muscle herniation. Clin Orthop Relat Res. 1989;(244):249-253.
  5. Kramer DE, Pace JL, Jarrett DY, Zurakowski D, Kocher MS, Micheli LJ. Diagnosis and management of symptomatic muscle herniation of the extremities: a retrospective review. Am J Sports Med. 2013;41(9):2174-2180. doi:10.1177/0363546513493598
  6. Mellado JM, Pérez del Palomar L. Muscle hernias of the lower leg: MRI findings. Skeletal Radiol. 1999;28(8):465-469. doi:10.1007/s002560050548
  7. Tong O, Bieri P, Herskovitz S. Nerve entrapments related to muscle herniation. Muscle Nerve. 2019;60(4):428-433. doi:10.1002/mus.26643
  8. Foresti M. Superficial peroneal nerve compression due to peroneus brevis muscle herniation. J Radiol Case Rep. 2019;13(11):10-17. doi:10.3941/jrcr.v13i11.3757
  9. Paolasso I, Cambise C, Coraci D, et al. Tibialis anterior muscle herniation with superficial peroneal nerve involvement: Ultrasound role for diagnosis and treatment. Clin Neurol Neurosurg. 2016;151:6-8. doi:10.1016/j.clineuro.2016.09.019
  10. Naffaa L, Moukaddam H, Samim M, Lemieux A, Smitaman E. Semimembranosus muscle herniation: a rare case with emphasis on muscle biomechanics. Skeletal Radiol. 2017;46(3):373-378. doi:10.1007/s00256-016-2553-x
  11. Zhou X, Zhan W, Chen W, et al. The value of ultrasound in the preoperative diagnosis of muscle herniation: A comparison with magnetic resonance imaging. Eur J Radiol. 2017;94:191-194. doi:10.1016/j.ejrad.2017.06.026
  12. Olch CL, Watson HK. Symptomatic forearm fascial hernia. J Hand Surg Am. 1996;21(4):693-695. doi:10.1016/s0363-5023(96)80030-x
  13. Guermazi A, Roemer FW, Robinson P, Tol JL, Regatte RR, Crema MD. Imaging of Muscle Injuries in Sports Medicine: Sports Imaging Series. Radiology. 2017;282(3):646-663. doi:10.1148/radiol.2017160267
  14. Flores D V, Mejía Gómez C, Estrada-Castrillón M, Smitaman E, Pathria MN. MR Imaging of Muscle Trauma: Anatomy, Biomechanics, Pathophysiology, and Imaging Appearance. Radiographics. 2018;38(1):124-148. doi:10.1148/rg.2018170072
  15. Beggs I. Sonography of muscle hernias. AJR Am J Roentgenol. 2003;180(2):395-399. doi:10.2214/ajr.180.2.1800395
  16. Dierickx J, Vanhoenacker F. Muscle Herniation: An Often-Missed Pseudotumor. J Belg Soc Radiol. 2020;104(1):62. doi:10.5334/jbsr.2294
  17. Sara L. Foreign body misdiagnosed as myofascial herniation of tibialis anterior muscle. Journal of orthopaedics for physician assistants. 2021;9(2). doi:10.2106/jbjs.jopa.20.00038
  18. Kotha KMR, Tandra VS, Murthy GVS, Vutukuri SR, Vyjayanthi Y. Tibialis anterior partial rupture mimicking muscle hernia: a rare case report. J Clin Diagn Res. 2014;8(10):LD08-9. doi:10.7860/JCDR/2014/10410.5056
  19. Dönmez G, Evrenos MK, Cereb M, Karanfil Y, Doral MN. Double layer repair of tibialis anterior muscle hernia in a soccer player: a case report and review of the literature. Muscles Ligaments Tendons J. 2015;5(4):331-334. doi:10.11138/mltj/2015.5.4.331
  20. Wolfort GF, Mogelvang C, Filtzer HS. Anterior tibial compartment syndrome following muscle hernia repair. Arch Surg. 1973;106(1):97-99. doi:10.1001/archsurg.1973.01350130095022

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