Can I sue a landlord for an injury caused by a broken staircase or railing in Ontario?

Yes. A landlord responsible for maintaining a rental property's structural elements can be liable under the Occupiers' Liability Act for an injury caused by a defective staircase or railing, provided the landlord knew, or reasonably should have known, about the defect and had a reasonable opportunity to fix it before the injury happened. This is why the strength of a claim often turns heavily on how visible or previously reported the problem was - a wobbly railing that a tenant complained about weeks earlier makes for a much stronger case than a hidden structural flaw that no one could reasonably have detected through ordinary observation.

Applicable building code requirements can be relevant context for what a reasonably safe staircase or railing should look like, though a code violation on its own does not automatically prove negligence; it is one factor among several a court considers. Maintenance request records, photographs of the condition before and after the incident, and any prior complaints from you or other tenants are usually the most important evidence in claims like this, which is why documenting a hazard as soon as it is noticed is genuinely worth doing, even before anyone is hurt.