Acute pain flare-up of knee osteoarthritis (KOA) is a common disease in orthopedics and is mainly treated with analgesic drugs. Patients usually refuse to take western medicines orally owing to gastrointestinal side effects or unsatisfactory treatment results. We report the case of a 69-year-old woman who had an acute pain flare-up of right KOA induced by long-distance walking. As the patient refused medication, we used electroacupuncture (EA) to relieve her symptoms. EA with a 2-Hz frequency and a 1-2-mA intensity had an analgesic effect on the acute pain flare-up of KOA. After 12 weeks of EA intervention, the bone marrow edema-like lesions (BMLs) improved significantly, as depicted on magnetic resonance imaging of the knee joint. However, more powerful evidence is needed to understand the mechanism of the EA technique that alleviates BMLs of KOA.