Dunne,
I would suggest that you get a physiotherapist/athletic trainer to palpate the glute medius. Often times it has been found that this area is very tender and the muscle is almost in spasm.
The glute medius muscle is responsible for a large amount of control at the knee. If this is not working to its full potential it only leads to problems.
The ankle joint might also have limited range of motion (loss of dorsiflexion) which might be causing the problem.
You have to think of it in terms of “pain site vs pain source”.
Personally I would try all avenues prior to injecting.
Thanks,
Jim