A chondroplasty means the cartilage
is being smoothed out, and loose or unstable parts are removed.
The patella is the kneecap, and the medial side is the inner side. In short, the answer is the cartilage of the inner side of the kneecap was smoothed out.
Tilting of the kneecap can occur for a number of reasons. Treatment most often is done with therapy, but surgery may be an option.