Sudden Knee Buckling During Gait Caused by Infarction of the Paramedian Pontine Artery: A Case Report.

This case report describes a female in her 90s with an infarction of the left paramedian pontine artery (PPA) who presented with sudden knee buckling during gait. Upon admission to the convalescent rehabilitation ward, she exhibited motor paralysis, ataxia, and contralateral body lateropulsion, making standing difficult. At the interim evaluation, she was able to ambulate under supervision with a walker; however, knee buckling occurred at gait initiation and during turning. Surface electromyography of the right rectus femoris and biceps femoris during these episodes showed abnormal muscle activation. It was inferred that reduced antigravity muscle output via the vestibulospinal tract, impaired motor processing due to paresis, delayed activation timing from ataxia, and global postural control deficits collectively contributed to the knee buckling. A comprehensive physiotherapy program was implemented. Subsequently, her functional scores improved substantially from admission to discharge, including a marked increase in the Berg Balance Scale (BBS: 4 → 47) and motor items of the Functional Independence Measure-Motor domain (FIM-M: 17 →52). Motor paresis, ataxia, vestibular dysfunction, and postural control deficits improved, and knee buckling resolved. To our knowledge, this is the first report indicating that PPA infarction can cause sudden knee buckling during gait.