I have sciatica and have been prescribed tramadol I have now noticed a lot of unexplained bruises on my legs could this be connected to sciatica?

No. Bruising is not related to sciatica. It could be related to any medications you could be taking. See your doctor to evaluate thus further.
Bruises. I'm not aware that sciatica causes bruises. You might experience some side effects from medication or drug interaction. Please see your doctor for evaluation.
Erythema nodosum. If, as it sounds, your bruises may be erythema nodosom which can arise for a multitude of reasons, one of which is a drug reaction. Normally these bruises will subside over time without treatment. If the bruises become very painful consult your doctor for relief.