Howard hasn't played since Jan. 30 because of edema in his right knee.
"He is starting to do a combination of treadmill and floor stuff, which is a good sign," McHale said Saturday night. "They're going slow. They want to make sure that they have a handle on it."
In early February, Howard underwent a bone marrow aspirate injection and started rehab immediately. The team said Howard would be out four to six weeks and that Howard's status would be evaluated after four weeks.
McHale has said he is not sure when Howard will return but expects him before the end of the regular season.
Howard is averaging 16.3 points and 11 rebounds in 32 games this season.
Information from The Associated Press was used in this report.