The Lanarkshire team are still in the chase for a Europa League qualifying spot, with Aberdeen and Dundee United.
But Kerr is happy to be available once more after a mysterious back problem tuned out to be growing pains, as he looks to start his third game in succession.
The former Birmingham player hopes he has put the problems behind him so he can get on with his career, starting with the visit from Celtic.
Kerr said: "It's always a game you look forward to and I'm just pleased that I am available for selection.
"It was a really strange one. I had this back niggle that I couldn't get rid of and seemed to be getting worse whatever we did.
"It turned out that I had gone from 6'3 to 6'4 ½ and that had been what the problem was. I hadn't expected my body to still be growing! Now I'm fully fit and raring to go.
"I'm a Motherwell lad and they stuck by me when we didn't know what was wrong with me.
"It's my job to repay them and now that I'm fit again I'll give them everything I've got whenever I'm selected to play."