I'm 5-feet 4-inches tall and only 107 pounds, but have extremely loose skin at my...
Generally speaking, lipoplasty (liposuction) does not tighten loose skin. It is difficult to design skin-tightening procedures around the knees because the necessary scars are difficult to hide; however, there are procedures that can achieve improvement in this area. A combination of lipoplasty with some type of skin tightening procedure could be the answer, but this would have to be evaluated in a personal consultation with a qualified plastic surgeon.
This is an extremely difficult area and a common cause of disappointment for patients after liposuction of the knees in the presence of excessive wrinkled skin. I would recommend a thigh lift if the excess skin is also present in the mid and upper thighs. This may alleviate some of the excess in the knees. There is no way to fully rid the area of the excess skin, however.