Hi. I Had TKR On November 28. Recovery Is Proceeding

Hi. I had TKR on November 28. Recovery is proceeding normally. Flexibility is 115 degrees and I can get to 120 when my PT tortures me. However I get an ache/pain at the joint / surgical site when I sigh or exhale hard. It lasts as long as the exhale takes then goes way until my next one, about every 15 - 30 seconds. It doesn't happen during exercise. Is this something to be concerned with? Thank you.