Unsteady gait, dragging one leg, growling! HELP!!

I'm new to this forum, but need advice ASAP. My cat, Mary, is a 5 year old mixed breed. She is obese, 22 1/2 pounds. My other cats are all normal weight. Yesterday when I was brushing her, she was stressed. About a half hour later she was on the back porch walking and she all of a sudden growled, fell to her side her left leg stretched out and when she tried to stand up, she had an unsteady gait and walked in circles. She then laid down on the chaise lounge and my other cats gathered around her to lay next to her. The rest of the night I watched her very closely and she seemed okay. Today it happened again. I'm wondering if she is having mini strokes or threw a blood clot? I will take her to the vet in the morning, she is resting quietly now. Any ideas?

Yes, it's definitely a vet matter.

Does she seem confused or weird in the eyes or anything like that? If not, I wonder if it's arthritis or a pulled muscle---something to do with her leg and not a neurological thing. I think if it were a stroke she'd be disoriented and have erratic eye movements.

I hope everything works out!!

No, her eyes are normal, pupils not dilated or constricted. What about hypertension? 

It's difficult to get a blood pressure reading on a cat. Whatever happens it probably is time to start focusing on dropping some weight.

Emergency vet now.

I'd take her to the emergency clinic.  This could be life threatening.  Poor baby.  Hope she's OK.

Emergency vet now!!

On our way to the vet right now! Thanks everyone!

What did the vet say?