Deep tissue hypersensitivity to pressure pain in individuals with unilateral acute inversion ankle sprain.

Objective: The objective of this study was to investigate whether pressure hypersensitivity over deep tissues is a feature of acute inversion ankle sprain.

Design: This is a cross-sectional study.

Setting: No study has previously investigated peripheral and central sensitization mechanisms in a clinical acute pain model such as inversion ankle sprain.

Patients: 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.

Outcomes: 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.

Results: 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.

Conclusions: 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.