Persisting Pain Following Total Knee Replacement: A Case Series Exploring Frequency Specific Microcurrent as a Therapeutic Approach

Background: Persistent pain following total knee replacement (TKR) remains a clinical challenge, even after postoperative rehabilitation. Its contributors may be multifactorial, and some patients continue to experience symptoms despite substantial improvement following surgery. Frequency Specific Microcurrent (FSM) is an electrical modality explored in several clinical conditions; however, evidence of its use in persistent post-TKR pain management remains limited. Objective: This paper aimed to describe the clinical outcomes following individualized FSM treatment in four patients presenting with different pain-related symptoms following TKR. Methods: This retrospective observational case series included four patients who presented with persistent symptoms after unilateral or bilateral TKR and had completed postoperative physical therapy rehabilitation. Individualized FSM protocols were selected according to each patient's clinical presentation. The outcomes were documented using the Numerical Pain Rating Scale (NPRS). Additionally, knee range of motion (ROM), qualitative sensory examination, pressure algometry, and the Central Sensitization Inventory (CSI) were used where applicable. Follow-up findings were recorded at available time points. Results: All four patients demonstrated improvement in at least one clinical outcome following FSM. In Case 1, bilateral knee pain decreased to 0/10 immediately after treatment, with improvements maintained at six months. In Case 2, right knee flexion increased by 15° without pain at the end of the assessed range, and the improvement was maintained at two months. In Case 3, knee pain and L3–L5 hyperesthesia were resolved and maintained at one-month follow-up. In Case 4, night pain substantially improved, and at three-month follow-up, NPRS was 1/10, and CSI decreased from 40/100 to 19/100. Conclusion: These cases describe favorable clinical changes following individualized FSM application for persistent symptoms after TKR. Given the small sample, heterogeneous presentations, absence of a control group, and individualized protocols, the findings are preliminary and warrant investigation in prospective controlled studies