Compiled By: Gabriel J. Gelves, D.O.
History: Thigh pain for the past several months with recent increased symptoms over the past 2-3 weeks since a straining type injury. Evaluate for hamstring injury.
Exam: Long and short axis fat and water weighted images of the bilateral thighs.
Findings and Differential Diagnosis:
An avulsion of the common hamstring tendon from the inferior perimuscular ischial tuberosity origin includes the biceps femoris, semimembranosus and semitendinosus tendons. The proximal portion of these tendons is retracted up to 4.5 cm. Adjacent perimuscular hemorrhage is present. Mild diffuse low-grade muscle strains are noted to involve these muscles. Mild subcortical osteoedema is seen along the right ischial tuberosity. Two small posttraumatic ganglion cysts are seen adjacent to the origin of the hamstring tendons in its displaced location.
Discussion:
Hamstring muscle strains are not uncommon and occur as a sudden event during eccentric muscle contraction (contraction while the muscle is lengthening). Injuries occur along the myotendinous junction most frequently as this is the weakest part of the muscle tendon complex. These are usually sports-related and involve the Biceps Femoris, Semitendinosus, and Semimembranosus as they span two joints and are eccentrically activated.
Muscle tears and avulsions will demonstrate high signal intensity in areas of edema or hemorrhage on conventional T2, fat suppressed T2 weighted FSE, and STIR wequences.
The axial plane is useful for demonstrating muscle retraction and atrophy. The coronal and sagitals provide a longitudinal view of the muscle group on one image.
The hamstring muscle group consists of the Biceps Femoris, Semitendinosus, and Semimembranosus. The Biceps Femoris originates on the posterior medial ischial tuberosity and inserts along the lateral aspect head of the fibula. The Semtendinosus arises just medial to the Biceps along the posteromedial ischial tuberosity, and inserts along the anteroproximal tibial shaft. The Semimembranosus originates along the anterolateral ischial tuberosity and inserts along the posterior medial tibial condyle.
Hamstring strains are divided into three grades.
Grade 1: Tearing of only a few muscle fibers. No loss of function, or permanent defect. Edema is seen as feathery T2 signal hyperintensity within the muscle or tendon. Convalescence can be as short as two weeks.
Grade 2: Larger area of partial muscle tearing with loss of some muscle strength. Hemorraghe with increased peritendonous and myotendinous T2 signal. Tendon may appear thin, lax and irregular. Recovery is usually no less than 4 weeks.
Grade 3: Complete rupture of the muscle with interruption of the linear hypointense tendon or myotendinous junction signal. Near complete loss of function. Psuedomass of tendon retraction. Hematoma and ganglion formation may be present. Poor prognosis with at least 8-10 weeks of convalescence with or without surgery.
