Case Diagnosis: Quadriceps Muscle Herniation
A healthy 34-year-old man was referred to physiatry clinic by orthopedics for diagnostic ultrasound evaluation of a left knee mass. He was involved in a bicycling accident 1 year prior to presentation resulting in pain superior to the left lateral knee, along with a visible mass seen only with knee flexion. Magnetic resonance imaging (MRI) of the region could not explain the etiology of this mass. Diagnostic ultrasound performed over the mass showed a herniation of the vastus intermedius into the vastus lateralis muscle, measuring approximately 1 cm wide and 0.7 cm high, that was most pronounced on knee flexion and minimally seen in extension. It did not result in any surrounding neurovascular compromise. This information was forwarded back to the service for further management.
Muscle herniation, defined as an abnormal protrusion of muscle through either an acquired or congenital fascial defect, is an uncommon phenomenon and most reported cases involve lower leg muscles. To our knowledge, there’s been no reported cases of vastus intermedius muscle herniation into vastus lateralis. Treatments for muscle herniations are typically conservative although rarely, surgical repair is necessary for larger defects or lesions with neurovascular compromise. MRI has traditionally been used to evaluate soft tissue injuries, including muscle herniations. Diagnostic ultrasound has been shown to be a convenient and cost-effective alternative for evaluating the size and location of muscle herniations. In our case, because of its dynamic capabilities, ultrasound was critical for the diagnosis allowing for visualization of the mass with the knee in flexion, a position not possible with MRI.