I am so very sorry to hear about your little Nikki. My primary concern is an injury to the neck, not necessarily doing something like jumping off the furniture and crying out, they can be walking around the house and have a disc herniation because of their anatomy. When she moves a certain way or lays in a position it likely causes her pain and extension of her leg provides some relief.
Here is more information on this condition:
Ideal is to have your veterinarian evaluate your dog to definitively diagnose the problem and start on appropriate medication to control the discomfort. Until you are able to do this please restrict activity (which often they are already doing themselves but that means no steps/ stairs and only carrying to go potty) and rotating warm and cool compresses on the shoulders/ neck in ten minute intervals to reduce pain and increase blood flow.
The only safe pain medications over the counter for dogs is aspirin. An aspirin dose for dogs is 5 mg/ pound every 12 hours with food
Please let your veterinarian know that you have administered aspirin if you take your pet into the office because it will effect what medications would be dispensed since aspirin requires a “washout period” of 48+ hours prior to changing to another non steroidal such as rimadyl, metacam, previcox.
Administer aspirin with food and if you note any reduced appetite, vomiting, diarrhea with administration then please discontinue its use. I would definitely advise not treating with aspirin at her age and a veterinary evaluation instead because they can dispense safer medication for her to control her pain with less potential side effects
You can also do light circular massage up and down the neck to stimulate blood flow if this is not too painful and will allow it.
To pick your dog up please use one hand between front legs and then scooping behind back legs to avoid pressure in the middle of the back. I have actually trained my little dogs to put their front legs on my forearm to minimize pressure on their backs / shoulders and the associated discomfort because they too will cry out if picked up a certain way due to back pain.
Please let me know if you have any additional questions I can assist with. I hope you are able to get your little one comfortable soon, truly.
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