Signs: Looking red and inflamed and sore, sores developing on the feet, reluctance to walk, reluctance to eat due to pain.
To help prevent: keeping nails trimmed, ensuring cage is always clean so they aren’t walking on soiled bedding, giving a good hay based diet with some good Vit c veggies included
However, Piggies hide their injuries and illnesses very well so being aware of what is normal so you can see the moment things start to look abnormal is going to go a long way to dealing with a problem early. By the time a piggy is in pain to stop eating, it could already be a well established problem.