BACKGROUND: Fat accumulation in the vastus medialis has been associated with the progression of knee osteoarthritis. Electrical muscle stimulation may reduce intramuscular fat accumulation by inducing contractions of the targeted muscle. We hypothesized that electrical stimulation of the vastus medialis would be associated with a reduction in intramuscular fat and improvement in self-reported symptoms during the observation period in a patient with knee osteoarthritis.

CASE REPORT: The patient was a 77-year-old man with Kellgren-Lawrence grade 2 right knee osteoarthritis. Because he also had hypertension and hyperlipidemia, he had maintained regular exercise habits, including aquatic walking; however, he discontinued these activities because of knee pain. Electrical stimulation was applied to the vastus medialis for 30 minutes per session, 3 times per week, for 4 weeks. Ultrasound echo intensity, an indirect indicator of intramuscular fat, and the Knee Injury and Osteoarthritis Outcome Score were assessed before and after the intervention. Compared with the pre-intervention value, vastus medialis echo intensity decreased by 13.7 arbitrary units (25.3%), and knee symptoms improved during the observation period. He resumed aquatic walking 2 weeks after electrical stimulation was initiated.

CONCLUSIONS: During the observation period, vastus medialis echo intensity decreased, Knee Injury and Osteoarthritis Outcome Score scores improved, and he resumed aquatic walking. However, because this was a single uncontrolled case and physical activity resumed during the intervention, these changes cannot be attributed to electrical stimulation alone; spontaneous improvement, behavioral reactivation, or a combination of these factors remain plausible. Controlled studies across different levels of disease severity are needed.

Keywords: Activities of Daily Living, Case Reports, Electric Stimulation, Osteoarthritis, Knee, Quadriceps Muscle, Ultrasonography