Without seeing the horse, the signs you are describing sound like a laminitic event. I would recommend having you vet out to assess your horse. Many times, acute laminitis is a secondary complication to a primary disease elsewhere in the body. Treatment of laminitis can only be successfully when treating the primary disease. Older horses can develop equine cushings disease which can predispose horses to laminitis. Here is a link to a paper on cushings and metabolic disease (Click Here
Management of the inflammation initially is critical in preventing acute laminitis from becoming chronic. Support of the foot in deep bedding, foam padding, setting the heels and toes back can help. Use of anti-inflammatories like bute are also advised.
It may only be associated with being out on lush pasture, in which case removing from pasture is critical, treating with bute, ect. However, I would have your vet out to assess the horse and determine if there is any underlying disease predisposing your horse to laminitis.
Hope this helps.