What To Do
Assess your horse's general health using the Whole Horse Exam (WHE), paying particular attention to rectal temperature and heart rate. Assess the foot for digital pulse and heat. Assess lameness at the walk. Look and feel for swelling in the heel and rear part of the pointing lower limb.
Share your findings and concerns with your vet. The severity of the problem usually depends on the degree of lameness and pain.
What Not To Do
Do not assume that this stance is normal for your horse. Usually it results from pain in the limb. Do not force the horse to walk forward if they strongly resist.