Painful Flexible Flatfoot Deformity: A Description of Posterolateral Ankle Trigger Point for Pain.

Background Flexible flatfoot deformity may be painful, and it is often difficult to pinpoint one painful area. Considerable variability of symptoms and areas of pain are noted in this condition. This study aimed to identify a reproducible area of pain and tenderness in these types of feet, implying a painful flatfoot. Methodology This study included 35 patients, comprising 23 males and 12 females, with 66 painful flexible flatfoot deformities representing the study group. The average age was 7.8 years (range = 2-15). In total, 31 patients had bilateral pain, and four patients had unilateral pain. The control group included 20 age-matched patients with normal painless feet. Results In 28 patients, pain was non-localized in the lower extremity. Overall, seven patients had non-localized pain in the foot and could not identify a point of maximal tenderness. A new trigger point for pain was identified in all patients, 1.5-2 cm below and 1.5-2 cm posterior to the tip of the lateral malleolus, well behind the peroneal tendons. No pain was reported by the control group. Conclusions A new constant trigger point for pain was identified in all patients with painful flatfoot deformity. It is hypothesized to be due to the overloading of the posterolateral corner of the talocalcaneal joint or impingement on the calcaneofibular ligament secondary to the heel valgus. We believe that the presence of this trigger point will help clinicians confirm flatfoot deformity as the source of pain, adding another tool in the evaluation and diagnosis of this condition.