Plantar fasciitis, the most common cause of heel pain, accounts for approximately 11-15% of foot symptoms presenting to physicians. In the United States, more than two million individuals are treated for PF on an annual basis. The term Plantar Fasciitis implies an inflammatory condition by the suffix 'itis'. However, various lines of evidence indicate that this disorder is better classified as 'fasciosis' or 'fasciopathy'. Details about etiology, pathogenesis, risk factors, diagnosis and general treatment strategies for plantar fasciitis have been provided in a series of comprehensive reviews recently. Briefly, both athletes and the elderly commonly present to physicians with plantar fasciitis, and the diagnosis of plantar fasciitis is usually based on the patient's history and clinical examination. It has been recommended in the literature to start treatment of plantar fasciitis with conservative treatment modalities, including physical therapy, stretching, inserts/orthotics etc. For patients not responding to conservative treatment for 6 months (between 10% and 20% of all patients) extracorporeal shock wave therapy (ESWT) should be considered. In case a patient does not benefit from ESWT either, surgical intervention should be taken into account.

Several randomized, controlled trials of ESWT with focused shock waves for chronic plantar fasciitis were published, demonstrating favourable results in the range of 50% to 70% after a followup period of three months after treatment. Besides this, a recent study demonstrated safety and efficacy of radial extracorporeal shock wave therapy (rESWT) for chronic plantar fasciitis (Gerdesmeyer et al., Am J Sports Med 2008 Nov;36(11):2100-9). These authors administered rESWT or placebo treatment in three sessions, each two weeks (±4 days) apart and evaluated the treatment outcome at twelve weeks and twelve months after the first session. The authors found a statistically significant (p \< 0.05) difference in the reduction of the mean Visual Analog Scale composite score between the patients treated with rESWT and the placebo-treated patients both at twelve weeks and twelve months from baseline.

To further evaluate the potential of rESWT to become a routine therapeutic modality in the treatment of chronic plantar fasciitis, the investigators of the present study identified the following questions not addressed in the study by Gerdesmeyer et al. (2008). First, it is unknown whether treatment success can also be reached by two rESWT sessions one week apart, rather than by three rESWT sessions each two weeks apart as applied by Gerdesmeyer et al. (2008). Anecdotal reports by colleagues in Europe indicated that this could indeed be the case. Second, immediate return to normal daily life activities (including sports activities) and normal daily shoe wear indicates that patients suffering from chronic plantar fasciitis and treated with rESWT experience profound pain relief already much earlier than three months after the first rESWT session, applied as first followup in the study by Gerdesmeyer et al. (2008).

Therefore the hypothesis was tested in the present prospective, randomized, double-blinded, placebo-controlled study that treatment of chronic plantar fasciopathy with two rESWT sessions one week apart will result in profound pain relief compared to placebo treatment already four weeks after the first rESWT treatment, lasting for at least six months.