Normal wear-and-tear on the knee can cause tissue, or cartilage, in the knee to soften over time forming chondral lesions. Worn out cartilage is often found during knee surgery for other conditions. Typically, surgeons will remove any worn out cartilage that is found using a procedure called debridement. However, the investigators do not know if surgically treating the worn out cartilage is better than leaving the tissue untreated, so it is necessary to compare the two. Patients who are found to have worn out cartilage during arthroscopy, will be randomly assigned to either receive treatment (debridement) or non-treatment (observation) of their cartilage. Patients without worn out cartilage will also be included in this study and observed postoperatively.