Henderson, 33 cost the Blades in access of £2,000,000 from Watford in July 2008 but following his released from relegated Leyton Orient this summer has joined the Iron on a free transfer. Despite joined Forest on trial he was in the last few days linked with a return to Bramall Lane as Nigel Adkins looks to bolster his strike force.
Elsewhere, former Blades Academy striker Jonathan Forte has seen his move to Barnsley (from Oldham Athletic) collapse after failing to agree terms.