I have pain on the side of the leg just below the knee. i was treated for acl but it does not seem to help. is it some other ligament?

Possibly: Quite possibly it is something else. An ACL injury would usually not cause pain in that area. Did you have an MRI? That would have shown which ligaments were involved. The lateral collateral ligament is in that area, as is the proximal fibula, and it is also an area supplied by the L5 nerve as well.

Possibly.: See a sports medicine orthopedic knee surgeon, who can determine the root of your problem.