I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is XXXXX XXXXX I'm a biologist with many years experience breeding rabbits. I'm sorry to hear of this incident.
While it's possible your rabbit has a broken bone, there are more common causes of hind leg paralysis. If Bun Bun was dropped, fell, or was twisted in some way, she may have an injury. It's common for injury to the spine, pelvis, or limbs to result in hind leg paralysis. Sometimes administering corticosteroids can help the rabbit heal.
Arthritis is another possible cause, but in a rabbit as young as yours, this is less likely. It can be treated with Rimadyl and/or glucosamine supplementation.
Degenerated or ruptured vertebral discs also cause this condition, but again, that would be uncommon in a rabbit so young.
The sporozoan parasite, Encephalitozoon cuniculi, is yet another possibility. It is treated with anti-parasitic medications, such as febendazole. I have found this to be the most common cause of hind leg paralysis in young rabbits which have not suffered an injury. Here's a site with much more information on hind leg paralysis and weakness:
Regardless of the cause, you'll need to take Bun Bun to a rabbit vet to diagnose the problem. She is not likely to get better on her own. The above causes are very different in their treatment, and the necessary drugs are available by prescription only. Here's a directory that will help you find a rabbit vet near you:
If you have further questions, just let me know in a REPLY. I hope Bun Bun recovers quickly.
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