Many rabbits suffer from what is commonly called "hock sores." These result when increase pressure on the bottom of the hock joint (the heal) causes the bone to push right down against the skin. Most rabbits have fur covering this area and many will have small callouses. In some rabbits whether it be breed (Rex) changes in posture due to arthritis or injury, obesity, poor housing (i.e., wire bottom cages) this condition becomes so severe that the area abscesses and ulcerates. Even running or sitting on an abrasive surface such as carpet can wear the hair away and leave the rabbit's foot vulnerable to what are essentially pressure sores. Overgrown toe nails force the rabbit to shift their weight off the toes and back on the heal - this will cause hock sores even in the fluffiest footed rabbits. The infection can quickly spread to the hock joint and into the bones of the foot and lower leg. This condition is not one of just the hock but, of the mid-hind feet and the front and back paws/toe pads as well. This condition can have serious and devastating consequences such as long term treatment/antibiotics, amputation, and even death.
Faith has ulcerative pododermatitis on all four feet. Recently, she developed an abscess along the midline of one hind foot despite already living on straw bedding - she now needs to be on long term duplocillin injections. I have recently made changes to her pen to prevent her from eating the walls (a whole other weird Faith problem) and at the same time added more straw to her pen to provide additional cushioning - it is now well over a foot deep in the back corner. I have used choroplast boards along the front of the pen as well to keep the straw from spilling out of the pen and all over the floor. Choroplast can be easily bent by scoring just one side of the board along the desired fold line and you can essentially form a large cage bottom or square pool and then set an xpen or NIC pen right inside. You could also use a toddler's wading pool surrounded by an NIC pen. Bales of straw can be purchased at local farms, feed stores, co-ops, TSC.
For anyone that has a rabbit that is struggling with "hock sores" or pododermatitis, I highly recommend building them a straw habitat. Even if they are only enclosed while you are at work and at night that will give them a tremendous amount of time where they do not have that direct pressure on their feet. I think this is a better solution than bandaging as it is preventative and curative. I also like to apply Harrison's HealX to the any sore or inflamed areas once of twice a day. Monitoring areas closely, for signs of abscess (swelling, heat, change in colour) are very important as well. BTW - straw is not nearly as dusty as hay and it is easy to keep the area clean. I scoop out any well used or soilded areas and replace with straw from other areas of the pen. Then, spread fresh straw in those areas. (Kind of like a horse stall.)
Anyway, it looks like a barn in that room, but Faith's feet are looking much better, and she is having a great time digging and tunnelling and burrowing down for naps. (I think the other rabbits are jealous!) This is about three-four bales of straw and she uses an extra one to sit and sleep atop. Aspen shavings are mixed in as well but, I will not add them anymore - I will just stick with the straw. Aspen is useful if your bunny pees in the straw.