This study is a prospective, longitudinal, multi-center, within patient evaluation of patients with articular cartilage defects of the knee who have had an inadequate response to a prior non-Carticel surgical treatment. Patients who met eligibility criteria were enrolled in the study. Subsequent to implantation with Carticel patients have follow-up every 6-months up to 48-months.

Inclusion Criteria:

• Provided written informed consent
• Documented history of at least one Grade III or Grade IV defect (modified Outerbridge classification) on the medial or lateral femoral condyle or trochlea
• Failed prior treatment for articular cartilage defects of the knee, e.g. inadequate response to a non- ACI surgical procedure to treat the lesion, within past 3 yrs
• Patient reported overall knee condition of 5 or less on the Modified Cinn Rating System
• patients must have had a cartilage defect located on the medial or lateral femoral condyle or trochlea which had an inadequate response to a prior arthroscopic or other non-Carticel surgical repair procedure

Exclusion Criteria:

• see above