How easy is it?

Ok i put my hands up i am a worrier, most the times over nothing and make something more than it is.. BUT how easy is it for a pup to pull a muscle or something .. I watch my dogs back legs constantly because of what happend with my previous staffy and him loosing the loss of his back legs due to spinal damage and sometimes i make myself believe his walking funny and no one else thinks he is (<-WORRIER!) BUT today i THINK vin has pulled a muscle in his one back leg .. he has a habbit of jumping onto the back of the setea and watching outside but sometimes he'll walk up the back of it and his one leg slips down the back of the cushion and i THINK he's pulled it doing it this morn?? i just wanna no how easy it is for em to pull a muscle he also runs round like a loon jumps of n on chairs when his in a hype and lately after this fly that wont b**ger of! lol ?
I HOPE its not spinal and if im right he wont have cuz his not fell on his back or anything and he dont seem to be in any pain when i touch his back or legs ?
Im doing everyones head in with worrying lol.

Poor Vinnie, they do run about like loons, and the problem is cause of there high pain threshold they rarly show any symptoms of pain. Just because what happened to first dog though doesn't mean it will happen again so please stop worrying slightly. If you are seriously worried then the only thing is to have a vets check him over. I always ask to see the nurse as they generally don't charge me. I hope he's ok let us know

Thankyou! i will try lol