What Causes Pain In The Hips?

My mum is 65 years old and generally well unless for the fact that she is experiencing pain in both hips. This pain occurs suddenly when she is about to make some movement and after short walks to the point of impeding her mobility. She lives in a country where adequate health service is not readily available. She has been active all her life. She is generally well an a bit overweight. What might be the problem?