Selective Nerve Ablation for Chronic Knee Pain: A Retrospective Study

Overview

SAVE-KNEE is a single-center retrospective observational cohort study evaluating outcomes of ultrasound-guided cryoneurolysis, radiofrequency ablation and chemical neurolysis for chronic knee pain in routine clinical care. The study uses existing clinical records from June 1, 2022 through May 14, 2026. May 14, 2026 is the fixed cutoff for both eligible treatment and follow-up observations. Later clinical observations are excluded from this analysis. The primary outcomes are changes from the pretreatment baseline in patient-reported 0-10 numeric rating scale (NRS) knee pain and WOMAC scores at available 1-, 6- and 12-month assessments before the cutoff. Secondary outcomes include pain response, documented adverse events and repeat procedures. Follow-up availability varies; a 12-month assessment is not required for inclusion. Treatment and follow-up were provided as routine clinical care funded by the Polish National Health Fund (NFZ), independently of this study. No treatment or additional visit is assigned for research purposes. Pain assessments were conducted in person or by telephone. When verbal assistance was needed, the final 0-10 rating was stated or confirmed by the patient.

SAVE-KNEE is a retrospective observational cohort study of existing routine clinical records at a single musculoskeletal rehabilitation center in Warsaw, Poland. The study evaluates patients with chronic knee pain treated with minimally invasive procedures targeting sensory nerves around the knee. The principal procedures evaluated include ultrasound-guided cryoneurolysis, radiofrequency ablation, and chemical neurolysis. Selected patients may also have received adjunctive treatments, including hyaluronic acid, collagen, prolotherapy, or corticosteroid injections as part of routine clinical care. Clinical effectiveness is evaluated using changes in patient-reported 0-10 NRS knee pain scores and WOMAC scores from baseline to available follow-up assessments at approximately 1, 6, and 12 months. Safety is assessed from procedure-related adverse events and complications documented in the available clinical records. Minor bruising at needle-entry sites was not systematically recorded; its incidence cannot be reliably quantified from these records. Additional analyses are intended to evaluate durability of response and clinical factors potentially associated with treatment outcomes, including patient characteristics, severity of knee osteoarthritis, previous knee arthroplasty, treatment method, and adjunctive therapies. Time perspective: Retrospective. This is a closed analysis of routine clinical records from June 1, 2022 through May 14, 2026. Both index treatment and included follow-up observations must fall within this period. Clinical observations after May 14, 2026 are excluded, even when they concern earlier treatment. Routine care may continue independently, but no future follow-up data will be added to this analysis. Treatment and follow-up were provided through the Polish National Health Fund (NFZ). No treatment or additional visit is assigned for research purposes. Pain assessment: Patients reported pain on a 0-10 numeric rating scale (NRS), including direct ratings at qualification and on the procedure day. The baseline pain score used for outcome comparisons is the rating obtained on the procedure day before treatment. When a patient had difficulty selecting a number at follow-up, verbal assistance included questions about pain severity, percentage or fractional improvement, and confirmation of a proposed numerical value. In every case, the final recorded 0-10 score was stated or verbally confirmed by the patient; it was not assigned solely by the clinician. The use and extent of assistance cannot be identified for individual observations in the available records. Routine follow-up at approximately 1, 6 and 12 months was conducted in person or by telephone, with a transition toward remote follow-up during the observation period. Patients reporting less than 50% improvement, adverse events or concerning symptoms were referred for in-person assessment. Follow-up mode therefore depended partly on clinical response and symptoms. Safety documentation: Concerning symptoms reported during routine follow-up were recorded with their nature and extent. Absence of complications was not explicitly recorded. Safety analyses therefore describe documented events; no event entry is not equivalent to a confirmed event-free assessment. Unit of observation: Enrollment refers to 746 individual participants. The approximately 1000 cases in the study title refer to treated knees rather than 1000 different people; some participants had both knees treated. Knee-level outcomes must account for the dependence of observations within a participant. Repeat procedures on the same knee are distinguished from contralateral treatment and analyzed separately from first procedures. During in-person pain assessments, patients used a visible 0-10 numerical scale with facial illustrations as an aid. Telephone assessments used verbal numerical ratings. These measurements are described as NRS rather than a continuous visual analogue scale. Ethics review: The Bioethics Committee at the Regional Medical Chamber in Warsaw reviewed the project under reference KB/1844/26 and determined that the retrospective analysis was non-experimental and outside its remit; it therefore declined to issue an opinion. This determination is the basis for the Not required review status. Observation cutoff: May 14, 2026. Outcomes at approximately 1, 6 and 12 months are analyzed only when the relevant assessment occurred on or before this cutoff. Later observations are excluded. Patients with shorter available follow-up are not assumed to have completed 12 months. The number of available observations and missing measurements will be reported separately at each time point. The cutoff is an administrative boundary for this retrospective dataset and is not the date of an ethics decision.