Yes, the connection has to do with the hip are as previously mentioned. Spasticity is at it's worst when legs are straight in extended position, as in standing or lying with legs straight. For most of us there is a point at which the spasticity releases when you start to bend from the hip. I am capable of mo ing my leg and foot enough to drive when I am seated and most of my leg is supported by the drivers seat.
One theory abou spasticity that makes sense to me is that it is our body's way of compensating for increased weakness. It allows us to stand and even do some stiff legged walking. Our bodies have amazing adaptive qualities. We used to say "even dysfunctional behavior has a function" when I practiced social work, meaning that it was all about meeting needs. The same may be true for our physical selves, so that spasticity is an attempt at maintaining function by our bodies.
I have also heard it described as classic symptom of central nervous system insult or injury, so in that way I suppose you could say it is related to nerve damage.
Kathy, 49 with PPMS,full time scooter.
Married to a wonderful man, mother to a darling 9 yr old boy