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.

Objective Pain experienced by patients with plantar heel pain has been associated with fascia thickness. It is possible that referred muscle pain may also be related to symptoms experienced by these patients. Our aim was to systematically investigate if the referred pain elicited by trigger points in the leg and foot musculature reproduces the symptoms in individuals with plantar heel pain and to determine the association of trigger points (TrPs) with pain and related disability. Methods A case–control study was conducted. Thirty-five individuals with unilateral chronic plantar heel pain and 35 matched comparable healthy controls participated. An assessor blinded to the subject’s condition explored TrPs in the flexor hallucis brevis, adductor hallucis, quadratus plantae, and internal gastrocnemius. Pain and related disability were assessed with a numerical pain rating scale (0–10), the Foot Function Index, and the Foot Health Status Questionnaire. Results The number of TrPs for each patient with plantar heel pain was 4 ± 3 (2.5 ± 2 active TrPs, 1.5 ± 1.8 latent TrPs). Healthy controls only had latent TrPs (mean = 1 ± 1). Active TrPs in the quadratus plantae (N = 20, 62.5%), and flexor hallucis brevis (N = 19, 59%) were the most prevalent in patients with plantar heel pain. A greater number of active, but not latent, TrPs was associated with higher foot pain variables (0.413 < rs < 0.561, P < 0.01), higher impact of foot pain (0.350 < rs < 0.473, P < 0.05) and worse related disability (–0.447 < rs < –0.35456, P < 0.05). Conclusions The referred pain elicited by active TrPs in the foot muscles reproduced the symptoms in patients with plantar heel pain. A greater number of active TrPs was associated with higher pain and related disability in patients with plantar heel pain.

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Objective To assess the potential relationship between demographic (age, gender, body mass index, height, weight), clinical (affected side, duration of symptoms, health-related quality of life), psychological (depressive levels) or neuro-physiological (pressure pain sensitivity and number of trigger points -TrP-) outcomes with foot function and pain intensity in patients with unilateral plantar heel pain (PHP). Methods Fifty-four patients with PHP (48% females) were recruited. Demographic data, months with pain, time in standing position, depression, pressure pain thresholds (PPTs), number of TrPs, health-related quality of life, function and pain intensity were collected. A multivariable correlation analysis was performed to determine the association between the variables and a regression analysis was conducted to explain the variance in function and pain intensity. Results Pain intensity was negatively correlated with symptoms duration and calcaneus bone PPT and positively associated with gender, time in standing position and number of TrPs. Function was negatively correlated with PPTs on calcaneus bone, flexor digitorum brevis and abductor hallucis muscle and quality of life, and positively correlated with age, gender and depressive levels. Stepwise regression analyses revealed that 60.8% of pain intensity was explained by female gender, calcaneus PPTs, time in standing position, and function. Further, gender, quality of life, age, depressive levels and calcaneus bone PPTs explained 52.4% of function variance. Conclusions This study found that demographic, clinical, psychological and neuro-physiological variables can play a mutual interaction in function and pain intensity in patients with unilateral PHP. These findings could guide clinicians into the identification, prevention and treatment of PHP risk factors.