Musculoskeletal Ultrasound-Guided Micro-Needle-Knife Intervention at the Deep Fascial versus Superficial Fascial Layers in Lateral Epicondylitis Patients: A Randomized Controlled Trial.

Background: Lateral epicondylitis (LE) is a prevalent musculoskeletal disorder causing persistent elbow pain and upper-limb dysfunction. While micro-needle-knife (MNK) therapy has shown promise for musculoskeletal pain, its optimal anatomical target and intervention depth remain poorly defined. Patients and Methods: 70 participants with unilateral lateral epicondylitis (mean age, 39.91±12.41 years; 40 women, 57.1%) were randomized 1:1 to receive musculoskeletal ultrasound (MU)-guided micro-needle-knife intervention targeting either the deep fascial (DF) layer or superficial fascial (SF) layer at two anatomically defined forearm interfaces corresponding to LI10 and TE9. Both groups underwent 12 treatment sessions over 4 weeks. The primary outcomes were Visual Analog Scale (VAS) for pain and Pressure Pain Threshold (PPT) assessed at baseline, week 1, 2, 3, 4, and 8. Secondary outcomes included Pain-Free Grip Strength (PFG) and Mayo Elbow Performance Score (MEPS). Results: The DF group demonstrated significantly greater and earlier reductions in pain compared with the SF group. At week 1, 42.9% of participants in the DF group achieved mild pain levels (VAS ≤3), compared with 8.6% in the SF group (P < 0.001). The odds of achieving over 50% pain reduction in VAS pain score were higher in the DF group at both week 4 (OR 3.25, 95% CI: 1.72 to 6.19) and week 8 (OR 2.50, 95% CI: 1.67 to 3.75). Improvements in PPT, PFG, and MEPS were consistently greater in the DF group across all post-treatment time points (all P < 0.001). Specifically, the DF group achieved a median VAS reduction of 3 (2, 4) at week 4, which was significantly larger than the 2 (1, 3) observed in the SF group (P < 0.001) and exceeded the established minimal clinically important difference (MCID) of 1.5 points for LE. No serious adverse events were observed. Conclusion: Over 8-week follow-up period, musculoskeletal ultrasound-guided MNK targeting the deep fascial layer demonstrated superior efficacy and comparable safety to superficial fascial intervention for LE, supporting anatomically targeted, MU-guided fascial interventions as a promising short-term rehabilitation strategy. Clinical Trial Registration Number: ITMCTR2025001055.