How should I proceed with claiming for my treatment with the AIA policy?

Base on your description of your symptoms, it doesn't warrant a hospitalisation. Nowadays AIA is getting very strigent with claims vetting. Even if u can get the specialist to ward u just for the MRI, there will still be a risk claims can be denied on the basis of 'medically unnecessary'. If u are using their panel of doctors, the chance of warding will be likely lower. It isnt just about the doctor's diagnosis, it is also whether certain actions are in line with common practice, and necessary. There needs to be justification to why MRI needs to be done in-patient rather than out-patient.

You might want to just consult with an orthopedic specialist first. Based on my experience, MRI are typically not needed for an experienced orthopic specialist. They are usually able to make clinical diagnosis, without the need for radiology. Radiology will typically be needed if the specialist needs to confirm his diagnosis for surgery/suspicion of complications. A typical first consultation with specialist will cost about $200-$300. If radiology is needed to confirm any suspicion, u can decide again later. In event of hospitalisation is required after that, u will be able to claim them as prehospitalisation benefits.

Do you have a personal accident policy that has a medical reimbursement/expenses portion?

Add me on facebook if u require more assistance.

Well, the main aim of hospitalisation plans are to cover for medical conditions that are more serious and require treatment from the hospital.

It would be good if you can consult your agent first, but if the problem is really that serious, you should seek professional help immediately instead of worrying about bills. No agent can guarantee that your treatment can be 100% claimable by through the hospital plan, what matters most is the diagnosis from the doctor itself and it is the doctor's diagnosis that affects the claims.

Perhaps you can try approaching a poly clinic first, so that you get a referral into the hospital/specialist if the doctor deem it serious enough. Do also note that you can claim up to $600 per year from your Medisave for MRI scans.

On a separate front, is your pain due to an accident, if you have a PA plan, it should be a problem claiming from that.