Comprehensive assessment of lower limb coordination during the heel strike phase in Parkinson’s disease

Parkinson’s disease (PD) is character rised by numerous motor symptoms, including impaired coordination of the lower limbs, which reduces stability. The heel strike phase is crucial in gait, as it follows the single step phase and precedes the transfer of weight between limbs, requiring precise control to maintain balance. Impaired coordination during this phase can therefore compromise gait and stability. Therefore, this study aimed to investigate physiological coordination patterns of the lower limbs during the heel strike phase and identify potential alterations in patients with PD. Twenty-three patients with PD and 23 healthy controls participated in this study. Gait of each participant was recorded with a stereophotogrammetric system with 55 reflective markers and data were trimmed to ±15 milliseconds and analysed to assess joint coordination of ankles, knees and hips. Lower limb joint coordination was assessed through pairwise correlations of their acceleration time series. The results showed that PD patients exhibited reduced coordination during the left heel strike, involving all three joints of the left lower limb and ankle and hip of the right lower limb. However, increased coordination between knees was observed, possibly indicating compensatory mechanisms. Furthermore, the difference in coordination between each PD patient and the average coordination of the healthy control group significantly correlated with both disease duration and UPDRS-III scores, highlighting the association between coordination impairments, PD severity, and disease progression. In conclusion, individuals with PD show significant alterations in lower limb coordination during the heel strike phase. These alterations are associated with disease severity and progression, emphasising the need for targeted interventions to address gait dysfunction in PD.