When you take mag ox orally you get about 8mg absorbed.
That is the amount in an egg.

It is NOT enough. You need 350-400mg a day ABSORBED.

And yes, you can have asymmetric cramping. If your circulation is not good on one side, less blood supply, more demand (you are favoring your injured leg) etc.

There is a nice adjustable shower stool that fits in a tub. I bought mine at Amazon.
http://www.amazon.com/Duro-Med-522-1...7892141&sr=1-3

It has been a life saver and way less expensive than the bath chairs in hospital supply stores locally.
You can sit on it comfortably and soak the legs in the tub,
Which is what I do. (my adductor injury precludes getting in and out of a tub anymore). It is very sturdy, and does not corrode!

There is also a magnesium cream:
http://www.kirkmanlabs.com/ViewProdu...ct_ID@124.aspx

You can rub this into the muscles but it is more pricey this way.

In a pinch I have made epsom salt soaking cloths and put them on my knee (on vacation-- where there is no bathtub)
This works, if you use a concentrated solution, and several applications, leaving them on for 10 minutes each. This is more time consuming, but it did work on my knee one summer.
You could make these compresses in the sink and sit on the toilet seat cover.. and not need to carry any heavy pans around.

Which ever way you choose, I think you will find huge changes with magnesium.

If you have poor circulation in that left leg, then oral mag cannot get to the endpoints in the tissue. So some heat on the back of the thigh, (not really hot) may improve that.
Too much heat, and for longer than 20 min actually stimulates nerve pain for many people..and causes a pain loop of worse symptoms.