Deep Tissue Hypersensitivity to Pressure Pain in Individuals with Unilateral Acute Inversion Ankle Sprain

Abstract

The objective of this study was to investigate whether pressure hypersensitivity over deep tissues is a feature of acute inversion ankle sprain. This is a cross-sectional study. No study has previously investigated peripheral and central sensitization mechanisms in a clinical acute pain model such as inversion ankle sprain. Twenty individuals with unilateral inversion ankle sprain (10 women/10 men, age: 31 ± 7 years) and 19 comparable healthy controls (11 women/8 men, age: 30 ± 6 years) participated in this study. Pressure pain thresholds (PPTs) over anterior talofibular, calcaneofibular, and deltoid ligaments; the lateral and medial malleolus; the tibialis anterior muscle; second metacarpal; and median, radial, and ulnar nerves were bilaterally assessed. The analysis of variance (ANOVA) revealed that PPT levels over the affected anterior talofibular (P = 0.048) and calcaneofibular (P = 0.002) ligaments, and over the affected lateral malleolus (P < 0.001) were lower compared with the non-affected side within patients and both sides in controls. The patients also showed bilateral lower PPT levels over the deltoid ligament than controls (P < 0.05). No significant differences for PPT over the medial malleolus; the second metacarpal; the tibialis anterior muscle; and the median, ulnar, radial nerves were found. Significant negative correlations between intensity of ongoing pain and PPT over the anterior talofibular and deltoid ligaments were found: the higher the pain intensity, the lower the PPT. This study showed the presence of localized pressure pain hypersensitivity over ankle ligaments in patients with unilateral acute inversion ankle sprain, confirming the presence of localized peripheral sensitization.