physical examination like doing SLR and other tests would definetly help to some extent to localize the source of symptoms.However to exactly find out the extent of severity and nature of lesion Wikipedia reference-linkMRI has its own role.In some cases pain may limit the examination is such cases to radiological examination helps.So the physiotherapist should do the examination even if the physician has already diagonsed which helps him to formulate his hypothesis and work out on the cause.