Gait and any form of locomotion are highly complicated with many pieces necessary to achieve clean, smooth, coordinated motion.
Failure in only one piece of the puzzle can result in profound unhinging of the entire system because of the entangled nature of the feedback loops.
“ Proprioceptive feedback from extensor muscles during the stance phase ensures that the leg does not go into swing when loaded and that the magnitude of extensor activity is adequate for support. Proprioceptive feedback from flexor muscles towards the end of the stance phase facilitates the initiation of the swing phase of walking. Evidence that muscle afferent feedback also contributes to the magnitude and duration of flexor activity during the swing phase has been demonstrated recently. The regulation of the magnitude and duration of extensor and flexor activity during locomotion is mediated by monosynaptic, disynaptic, and polysynaptic muscle afferent pathways in the spinal cord. In addition to allowing for rapid adaptation in motor output during walking, afferent feedback from muscle proprioceptors is also involved in longer-term adaptations in response to changes in the biomechanical or neuromuscular properties of the walking system.” - Lam and Pearson
Neuroscientist. 2004 Jun;10(3):247-59. Cerebellar control of balance and locomotion. Morton SM1, Bastian AJ.