How do I tell if my puppy has myotonia congenita?

That description — stiffness that improves with movement — is the hallmark of myotonia congenita. Signs often appear when puppies start walking. Affected dogs have a stiff, uncoordinated gait sometimes described as 'wooden' or 'bunny-hopping,' and muscles may visibly bulge or appear overdeveloped. The stiffness is most noticeable after rest and typically improves with activity. It's caused by a mutation in the CLCN1 gene affecting chloride channels in muscles. It's seen in Australian Cattle Dogs and Border Collies. A DNA test for CLCN1 confirms the diagnosis. Our vets can help you get a proper workup started.