Extracoporeal shock wave therapy(ESWT) was perfomed on the plantar fascia of chornic plantar fasciitis patients. Pre-ESWT and post-ESWT pain intensity, sonography and sonoelastrography of the plantar fascia was checked. Our hypothesis is that the plantar fascia stiffness increased after ESWT as clinical symptom improves.

For patient who met the inclusion criteria, we check sonography and sonoelastography for their plantar fascias and obtain a thorough evulation questionaire for clinical symptom and pain condition and intensity in various conditions, also SF-36 questionaire first. Inform consent was done.

After the ESWT, we follow patient with questionaire and sonography/sonoelastography at 1-week, 1-month, 3-month, 6-month, 9-month, and 12-month post-ESWT time.

The colored sonoelastographic image was analysed by computer software "Image-J" with hue analysis method and relative stiffness of selected area within proximal plantar fascia wasa obtained for statistical analysis.

Inclusion Criteria:

• pain for more than 6 months，poor response to the conservative treatments
• Sonography showed plantar fasciitia>4.0mm)

Exclusion Criteria:

• Acute infection of soft tissue/bone
• Malignant primary disease
• Blood coagulation disorders
• Pregnancy
• Patients with pacemaker
• foot deformity