It is an arthroscopic procedure in which they cut out much of the scar tissue. They will usually do a manipulation at the same time as you are already under anesthesia. I had a manipulation planned and my Dr. wanted to scope me while I was out. He said there was so much scar tissue that I would not have been able to overcome it with P.T. So he performed the lysis procedure and it helped quite a bit.
https://www.arthroscopytechniques.org/article/S2212-6287(17)30061-0/fulltext