Difficulty with balancing and walking can occur in all stages of HD including premanifest and prodromal stages. Several factors related to HD make a person more likely to fall.
Walking evenly can be thrown off due to bradykinesia which is when walking pace is slowed or disrupted by stops and hesitations. Involuntary body movements caused by chorea can also throw off balance.
Declining cognition can also affect balance and movement because a person may have reduced visual perception and lack the focus necessary for avoiding hazards to prevent falls.
People with late-onset HD are most likely to experience issues with walking and balance as their first symptom.
Read here for tips on preventing slips and falls.