Your back pain
may have offset your gate and irritated your kn ee cause swelling of the knee. However, it is not uncommon for people with herniated discs or back problems to experience episodes of generalized swelling of one or both lower extremities. Sinceback problems are neurologic in nature the homeostasis of the circulatory system can be affected. Of course there's also concern for reflex sympathetic dystrophy
. We would need specific information on your physical exam and history. We would combine this with imaging
studies to get a diagnosis. I would also start with an x-ray of the affected me.