DeNovo NT Ankle LDC Study

Potential subjects are screened for study entry based on a preliminary review of the inclusion and exclusion criteria as it applies to their pre-operative status (unless otherwise noted). Inclusion Criteria: * Has an articular cartilage lesion(s) in the ankle for which arthroscopic or surgical intervention with DeNovo NT Graft is warranted or has had prior treatment with DeNovo NT Graft for an articular cartilage lesion(s) in the ankle * Has voluntarily signed the IRB approved informed consent * Is of stable health and is able to undergo surgery * Is male or female over the age of 18 at the time of consent * Is physically and mentally willing and able to comply with post-operative rehabilitation and routinely scheduled clinical visits. Exclusion Criteria: * Displays a high surgical risk as determined by the investigative surgeon * Is pregnant or breast-feeding * Has a clinically diagnosed autoimmune disease * Has an active joint infection or history of chronic joint infection at the surgical site * Has medical history that would likely make the subject unreliable for the study, or any combination of variables in the investigator's judgment that should exclude a potential subject