I didnt get an MRI when I tore my leg, if you're all for saving money, ask yourself, or the practitioner, 'Does the treatment change?'
The answer should be no, unless you need an operation, which is HIGHLY unlikely.
They should be able to find the problem without getting a scan, muscle tear treatment is all the same - breakdown scar tissue, increase bloodflow, allow to heal, repeat.
Learning more about the body, muscle groups, attachment points, referal pains etc. helps as well. Allows you to give the practitioner more of a detailed idea if you 'think' thats what might be causing the issue.