Widespread Pressure Pain Hypersensitivity in Musculoskeletal and Nerve Trunk Areas as a Sign of Altered Nociceptive Processing in Unilateral Plantar Heel Pain

Our aim was to investigate the differences in pressure sensitivity over musculoskeletal and nerve symptomatic and distant areas between individuals with plantar heel pain and healthy subjects and to determine the relationship between sensitivity to pressure pain, foot pain, and fascia thickness. Thirty-five patients with unilateral chronic plantar heel pain and 35 matched healthy controls participated. Pressure pain thresholds (PPTs) were assessed bilaterally over several nerve trunks (median, radial, ulnar, common peroneal, tibial, and sural nerve trunks) and musculoskeletal structures (calcaneus, medial gastrocnemius, tibialis anterior, and second metacarpal) by an assessor blinded to the subject's condition. Pain was assessed with a numerical pain rating scale (0-10), impact of foot pain was assessed with the Foot Function Index, and plantar fascia thickness was measured via ultrasound imaging. Analysis of covariance revealed lower widespread and bilateral PPTs over both nerve trunks and musculoskeletal structures in individuals with plantar heel pain (P < .001). Female patients showed lower PPT than male patients in almost all points (P < .001). PPT over the peripheral nerve trunks of the lower extremity were significantly associated with the intensity of pain at first step in the morning and with the foot function disability scale of the Foot Function Index (P < .05). This study found widespread pressure pain hypersensitivity over both nerve trunks and musculoskeletal structures in individuals with unilateral chronic plantar heel pain, suggesting the presence of a central altered central nociceptive pain processing. Pressure hypersensitivity over nerve trunks on the lower extremity was associated with higher pain intensity and related disability. PERSPECTIVES: This study found widespread pressure hypersensitivity over both nerve trunks and musculoskeletal structures in individuals with unilateral chronic plantar heel pain, as a manifestation of a centrally altered central nociceptive pain processing.