Denervation Edema in Vastus Medialis After Adductor Canal Block: Tracing Nerve Injury

In a patient with knee injury, an adductor canal block led to saphenous (sensory) neuropathy, but denervation edema in the vastus medialis indicated motor branch involvement. Fluid tracking into the femoral triangle likely compressed multiple femoral nerve branches.

• Saphenous nerve is purely sensory; denervation edema in vastus medialis means the motor nerve to vastus medialis is involved.
• The motor nerve to vastus medialis branches from the femoral nerve in the femoral triangle, so fluid or hematoma from the adductor canal injection likely tracked proximally.
• This case demonstrates that nerve injury after an adductor canal block can present with MRI findings of denervation in muscles supplied by the femoral nerve, not just the saphenous nerve.

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