Ultrasound-Guided Fascial Hydrorelease for Persistent Pain After Hamstring Injury

<b>Background:</b> Post-hamstring-injury residual pain may persist despite muscle-tissue healing and impairs athletes seeking early full recovery. Given their unclear cause, recent attention has focused on the role of fascial dysfunction and a method to restore fascial mobility, namely, hydrorelease (HR), involving the ultrasound (US)-guided injection of saline. We evaluated the clinical efficacy of HR for treating residual pain and ascertained the underlying pathological mechanisms. <b>Methods</b>: Seven patients (aged 17-49 years) with residual pain ≥8 weeks after hamstring injury were included. All exhibited localized tenderness and US findings of fascial thickening around the aponeurotic fascia (APF). HR with 6.0 mL saline-lidocaine solution (0.17% lidocaine) was performed and targeted the peri-APF loose connective tissues. Pain was evaluated using a numerical rating scale (NRS) before and after HR. Passive straight leg raise (SLR) was used to assess tightness. <b>Results</b>: Post-HR, the mean NRS score significantly decreased from 10 to 0.86 (<i>p</i> = 0.017). Four patients required a single HR session; three required two-four sessions. Post-HR, the tightness of all patients improved. Short-axis US of the posterior thigh revealed APF fascial thickening in the area of tenderness, including the posterior femoral cutaneous nerve (PFCN). No adverse events or recurrence occurred during the follow-up (mean: 6.6 months). <b>Conclusions</b>: HR targeting the peri-PFCN-APF effectively reduced residual pain following hamstring injury. These findings support the concept of "Perineural fascial pain"-a pathology wherein persistent pain originates not from direct nerve damage or classical myofascial pain syndrome but rather from the dysfunction of the surrounding fascia.