Sudden dog aggression - pain related??

Sandi has always got on fine with other dogs, but now she seems to have suddenly turned aggressive towards other dogs when she first meets them. She will sniff and wag her tail, and then suddenly snap at them. She has never done this before and I am trying to understand what is causing it. She is currently undergoing tests at the vets - they think she has something wrong with her hips or knee, as she is bunny hopping and limping a lot at the moment. Nothing obvious showed up on the x ray but they have referred it to a specialist. Could her joint pain be causing her aggression?? I have read on some websites that pain can cause dogs to be aggressive. I can't think of anything else that could cause this. We have also recently moved house, and she has started barking a lot more as well. I am just so confused as she was perfect before. We have just spent the weekend with family and 2 other dogs. Sandi snapped and jumped at them both on first greeting them, but after she had settled she got on with them fine. Any advice would be appreciated!

Any upset or unsettlement can cause her to react strangely if I walk my 2 a different place they have a look on there faces as if to say (you stark raving mad) they are such habbitual little creatures maybe she will need a little time to adjust to new surroundings and if she is in pain or discomfort then she may be showing aggression as a protection she cant understand whats going on she just knows things are not quite right.

She's probably anxious with the move, and possibly in discomfort with her hips/knees. Either of thees things could cause her to be a bit snappy.

I think you might need to be a little careful around other dogs until a) she's a bit more settled & b) her hips/knees have been sorted.

Thanks for the reassurance! We have been keeping sandi on the lead for the moment, but still making sure she sees lots of other dogs. Since doing this, there have been no problems. she has met, sniffed and wagged her tail on meeting lots of dogs. I am just going to be cautious with letting her off lead for a while in case she snaps again. We are going to the park tomorrow to make sure she can meet lots of dogs (keeping her on lead for now). I just hope plenty of socialisation will help ensure she doesnt make snapping at dogs a habit. Hopefully the vets will find out what is wrong soon and we can get her sorted out.

The move and pain could definately cause her to be a bit aggressive. I think you are right to keep her on lead. I would also avoid any high impact exercise so you don't make the problem any worse.