Perhaps the biggest challenge Wheatgrass faced after the loss of her hindlegs, was the “handstand” where she balanced her remaining mass on her front hooves.  
Being able to lift her hindquarters like this would be crucial for her to get in and out of a hindcart or getting up from a sitting position.  
Learning to do this in a smooth motion without just dropping her tender rear into the ground took weeks of training at the Canterlot rehabilitation clinic.