From the RWAF:
Older rabbit books blame sore hocks solely on filthy living conditions or wire floored cages. There's some truth in this, but some beautifully cared for houserabbits develop sore hocks, so it's not the whole story.
There are many predisposing factors, including:
1. Poor hygiene and damp bedding
2. Rex coats - less fur to protect the hock
3. Long nails - throw too much weight onto the heel
4. Obesity - increases the pressure on the foot
5. Immobility
6. Unsuitably flooring
7. Large breeds
8. Poor physical confirmation
Why do rabbits develop sore hocks?
As in so many other situations, to understand why rabbits develop sore hocks it's worth looking at the wild rabbit, and the conditions rabbit feet evolved to function well in.
The wild rabbit spends it's time moving about on grass and earth. These surfaces are compliant: they allow the toe nails to sink into the ground, encouraging the whole bottom of the foot to contact the ground and hence reducing the pressure on the foot (pressure = force divided by area).
In contrast, hard flooring means that the rabbit's toenails can't sink in. It doesn't make any difference whether the flooring is carpet, wood, vinyl, or plastic (with or without a covering of newspaper or wood shavings, for instance), all give the same result. Because the toe nails can't sink in, the front part of the foot is lifted off the ground, and the majority of the weight of the bunny is thrown onto the hocks, causing problems rather like a pressure sore. If the rabbit is heavy, or obese, the pressure on the hock is greater and problems more likely. Similarly, an immobile rabbit won't be hopping about in order to relieve the pressure on the hock area.
If the surface upon which bunny spends most time is abrasive (e.g. carpet), then additional problems can arise. This explains why spotlessly clean, dry houserabbits can run into problems with sore hocks.
What to look out for
Of course, not all rabbits develop sore hocks! If you take a close look at the heels of an adult rabbit, you'll usually find a small, bare, pale pink callused area right at the tip of the heel, covered by a fold of fur. This is normal.
"Sore hocks" are different - red and inflamed rather than the pale pink callused area. They may weep or become infected. In very severe, untreated cases, the tendons that run over the hock may move out of position, crippling the rabbit.
The usual site of trouble is at the tip of the heel, but severe cases may involve any or all of the weight-bearing part of the foot - and don't forget to check the front feet, too. It is worth making a habit of checking your rabbit's hocks every time you clip his/her claws.
Help, my rabbits has sore hocks! What happens now?
Sore hocks are notoriously difficult to treat, which accounts for the abundance of old wives tales for tackling the problem.
The first step is to tackle any underlying cause. Nails should be clipped as short as possible without damaging the "quick". Old, fat, immobile bunnies need to lose weight and may benefit from long-term pain killing medication to make them more comfortable and willing to move about. Any rabbit kept in damp conditons must have a far better level of care, and if the patient is a child's rabbit, the parents must take over responsibility for the care of the bunny.
Next, look at the surface the rabbit spends most time on. The perfect flooring for a rabbit with sore hocks is clean, dry grass, but indoor rabbits or those in hutches don't have access to lawns. Instead, you should aim to provide a compliant surface (where the toe nails can sink in, allowing the foot to function more as nature intended) where the rabbit spends most of its time.
We used to recommend that houserabbits with sore hocks should be "switched onto vinyl or plastic rather than carpet or vice versa". Now we have a better understanding of how sore hocks develop, we realise vinyl is a poor choice, unless the fundamental problem was dirty, damp conditions. Vinyl just isn't compliant enough to restore proper mechanics of the foot.
A far better option is to provide the rabbit with a deep bed of straw, perhaps on top of a towel or layer of peat, and place it where the rabbit likes to hang out. This needn't be too messy indoors if you find a big box with sides several inches high. The large under-bed storage boxes boxes work well. Veterinary fur-fabric bedding is also an excellent surface for your rabbit to rest upon, as it helps to spread the pressure on the whole bottom of the foot.
Don't forget that carpet is abrasive - some bunnies develop friction burns when leaping about on synthetic carpets, particularly when jumping off sofas and beds (it's not just the hind feet that are affected in some rabbits!) so you might need to discourage your rabbit from taking flying jumps off the furniture!
If your rabbit lives in a hutch all the time, you will need to undertake a full review of his living environment. Hutch-kept rabbits are likely to be relatively immobile and have spinal problems from lack of exercise over the years. As well as sorting out the flooring (switch to a deep bed of straw - wood shavings are abrasive, although you could use them on the floor and put the straw on top) your rabbit will need more exercise and space to move around in.
Most cases of sore hocks need to see the vet, for a thorough health check as well as treatment of the actual sore hock. More stubborn cases may benefit from referral to a veterinary dermatologist.
Treatment may include antibiotics; anti-inflammatory and pain-killing drugs; topical "artificial skin" preparations; and possibly bandaging, which is jolly good fun - bunnies usually hate bandages! Beware of applying creams and ointments without veterinary supervision - you may make the problem worse and prevent proper assessment of the affected area. And don't forget that unless the underlying problems are addressed, treatment is likely to be frustrating.
Also on the bunny forum on FB about this subject:
http://www.facebook.com/topic.php?uid=2220484255&topic=4817&nctrct=1239188696502
