Reducing lag and easing hip pain

I caught meningitis shortly after birth and clearly received a lot of injections, presumably in my bottom as my hip went stiff in the process. When I started walking, this stiffness "transferred" to my knee and I had an op to extend my quads when I was 5. The ensuing physiotherapy being painful/unpleasant/whatever, I only ever remember having some 70 degrees of flexion at the knee. This gradually reduced to less than 50 and I had the op repeated when I was 18 and now can flex to more than 90 degrees. I had some three months of physio afterwards to help build the quads etc. However, despite this, the later op left me with about 10 degrees fixed lag and another 5-10 variable. This means that it's not much good for standing on (especially one-legged :)) and when I do walk on it for any length of time, my hip starts to hurt. I can also add that after a year or more of cycling over 20 miles a day, the outer quad muscle just above the knee (sorry for not knowing its technical name!) appeared to be missing, developing instead a much larger muscle (comparing with my left leg) crossing from my right hip to the inside of my knee and a pronounced small triangle of muscles immediately above the knee.
The results of all this mean that when I try to use my leg for longer periods of time, walking/running, my hip starts to hurt and a small spasm in the muscle in front of the hip.
My question is whether there are exercises I can do to reduce these lags any further and anything else I can do to avoid the hip pain?