ObjectiveTo investigate the long-term effect of low-energy extracorporeal shock wave therapy (ESWT) for plantar fasciitis (PF) according to ultrasonography (US) findings.MethodsThirty feet of 25 patients with clinical diagnosis of PF were enrolled and divided into two groups (Apparent-US and Uncertain-US) according to US findings, such as plantar fascia thickening or hypoechogenicity. Inclusion criteria were symptom duration >6 months and a fair or poor grade in Roles-Maudsley score (RMS). ESWT (0.10 mJ/mm2, 600 shocks) was given once a week for 6 weeks. Numeric rating scale (NRS) and RMS were evaluated prior to each ESWT session, at short-term follow-up (one week after all ESWT sessions) and long-term follow-up telephone interview (mean 24 months after ESWT). Good and excellent grade in RMS were considered as treatment success.ResultsRepeated measure ANOVA demonstrated that NRS significantly decreased with time after ESWT up to the long-term follow-up (time effect, p<0.001) without group-time interaction (p=0.641), indicating that ESWT equally decreased pain in both groups. Overall success rate was 63.3% (short-term follow-up) and 80.0% (long-term follow-up). In comparative analysis between groups, success rate of Apparent-US and Uncertain-US at short-term follow-up was 61.9% and 66.7%, respectively, and 85.7% and 66.7%, respectively, at long-term follow-up.ConclusionIf other causes of heel pain are ruled out through meticulous physical examination and ultrasonography, low-energy ESWT in PF seems to be beneficial regardless of US findings. In terms of success rate, however, long-term outcome of Apparent-US appears to be superior to Uncertain-US.