Sorry to here about your hip mate.

Any exercise burns calories Ben, but if you consume to many you wont loose any weight.

You need to consume 6 small regular meals every three hours through out the day to boost your matabolism which will also burn calories along with the walking.

Take your weight in stones x 14 = ? then ? x 10 = daily calories needed to loose weight.

Hope that helps as a start mate with out getting to in depth.