Myofascial pain syndrome of the peroneus longus: biomechanical approach

OBJECTIVE: The aim of the study was to investigate the role played by anatomical (lower limb length discrepancy) and biomechanical (alterations in the dynamics of movement) factors in the pathophysiology of myofascial pain syndrome (MPS) of the peroneus longus. DESIGN: Patients affected with MPS of the peroneus longus of one side were submitted to either correction of their lower limb discrepancy by heel lift (6 patients) or normalization of altered biomechanical parameters during movement, as measured via ground-foot reaction analysis (g-f) by dynamic insoles (6 patients) for 60 days. At days 7, 15, 30, and 60, the effect of treatment was verified on painful symptoms [VAS scale, presence of the active trigger point (TrP) in the muscle] and on g-f parameters [peaks of vertical force (F1 and F3 of Fz) and of lateral shear force (Fx)]. RESULTS: Treatment with heel lift produced a moderate, significant reduction of the spontaneous pain and of the abnormal Fx peak in the affected leg after 7 to 14 days with no further improvement afterward. Treatment with dynamic insoles caused a marked, significant reduction of the pain at 7 days, with complete resolution of the painful symptoms at 30 days and concomitant disappearance of the active TrP in the muscle. It also produced a significant and progressive reduction of the abnormal Fx peak in the affected leg starting at the 7th day and continuing until the 60th day. CONCLUSION: Both anatomical and biomechanical alterations of the dynamics of movement play a role in the painful symptoms of MPS of the peroneus longus, but the biomechanical factor is by far the more prominent.