Plantar fasciitis is the classic and most common type of heel pain. Considering the costs for health care and the temporary disability not only for work, plantar fasciitis results in a substantial (and at least partially unnecessary) burden for the Swiss health care system and national economics. Nonoperative treatment is the mainstay of treating plantar fasciitis. However, so far no treatment has proven to be superior to others, and there is national and international lack of consensus of how to treat plantar fasciitis best. The investigators believe that the BTX-A injection in the gastrocnemius and the soleus muscles is currently the most promising non-operative approach, because it is considered to treat the disease at its origin (temporary weakening of the tight triceps surae muscle) as opposed to simply alleviate the symptoms (e.g. plantar cortisone and other injections, ESWT). However, to date there is no evidence in the literature that compares the new, promising technique of BTX-A injection into the gastroc-soleus complex to a sham (saline) injection and to the gold standard steroid injection at the plantar fascia insertion site. With the intended study, this gap is going to be closed.