I'm starting to think my GSD might have this........for the past year every 3/4 months she'll jump off the couch after a long sleep and her back legs can't take her weight for about 5 mins. At the start I put it down to cramp but as time goes on I'm thinking its leading onto something more serious
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She's 6 now, and this only happens once in a blue moon. I've googled other symptoms but she doesn't seem to be showing any ie she's happy to stand on back legs, chase a ball for ages, she goes up and down stairs fine.