I'm using co codamol and diclofenac for sciatica but have also started taking my partner's tramadol as pain is sharp up anddownleftleg. why is this?

Need additional eval: Sciatica is mostly caused by disc pathology such as a herniation or an annular tear. When sciatica becomes refractory and lasts more than 6 weeks despite medication, then you need to seek medical attention. Commonly you will be evaluated by MRI to see what the issue is along with a physical examination. Tramadol is an opioid medication that should be taken under the direction of a physician.

Spine Injury: This chronic pain in the distribution as you suggested is the result of an irritated nerve or facet joints or other injury typically in the lumbar spine (low back) which are caused by herniated disks, spinal stenosis or degenerative disc disease, etc requiring further evaluation by a spine specialist.