Injection of 10cc of a 15% dextrose and 0.6% lidocaine solution free of epinephrine in one injection site (lateral infiltration of the plantar fascia). This injection will be performed following posterior tibial nerve blockade (injection of 10cc of 1% lidocaine and 0.25% bupivacaine solution free of epinephrine behind the posterior tibial artery). The intervention will be administered every three weeks until symptoms are alleviated for a maximum of 5 injection sessions. Furthermore, patients must perform an at-home exercise program 3 times a week for a total of 12 weeks. The exercise program consists of 3 stretching exercises, 1 muscle release exercise and 1 strengthening exercise.

The Maryland Foot Score questionnaire will be used. This questionnaire assesses pain and function of injured foot using a summated rating scale of 10 questions.

The Brief Pain Inventory (short form) will be administered to assess pain intensity and pain-related functional impairment (physical and emotional). Four items assess the intensity of current pain and pain at ils least, worst, and average during the past day on scales form 0 ("no pain") to 10 ("pain as bad as you can imagine"). Seven more items measure pain-related functional interference in different domains (general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life) rated from 0 ("does not interfere") to 10 ("interferes completely").