Dog is wiggling butt when walking after TPLO surgery

My dog had a TPLO surgery almost 4 weeks ago. Overall he’s doing well - started to walk a little right after the surgery and now walking on the leash for 10-15 minutes at a time. He’d limp a little after longer walks, but usually recovers quickly. I noticed that he walks a little different - his butt moves side to side way more than before the surgery. This is especially noticeable when he’s excited and walks a little faster. He’s overweight. Should I be concerned? Thank you.