Efficacy and Safety Study of Intra-Articular Injections of Autologous Peripheral Blood Stem Cells Following Subchondral Drilling Surgery for the Treatment of Articular Cartilage Injury in the Knee

Inclusion Criteria: * Aged between 18 to 55 years at screening (20 to 57 years for the open-label extension) * Present for evaluation and treatment of knee pain, knee swelling, or knee mechanical symptoms due to cartilage lesions * Provide written informed consent * International Cartilage Repair Society (ICRS) Grade 3 or 4 lesions diagnosis from MRI scans of the target knee * All subjects must also satisfy at least 1 of the following inclusion criteria: * Isolated knee articular cartilage lesion (single lesion) estimated to be ≥3 cm2 as demonstrated on MRI scanning. Multiple knee articular cartilage lesions (multiple lesions) with at least 1 lesion estimated to be ≥3 cm2 as demonstrated on MRI scanning. Bipolar cartilage defects demonstrated on MRI scanning with at least 1 articular surface lesion to be ≥3 cm2. One or more cartilage defects involving the patello-femoral joint as demonstrated on MRI scanning with at least 1 lesion ≥3 cm2. One or more cartilage defects involving the tibio-femoral joint as demonstrated on MRI scanning with at least 1 lesion to be ≥3 cm2. Previously failed cartilage repair procedures (i.e., microfracture, osteochondral autograft transplantation surgery (OATS), ACI) Exclusion Criteria: * Three or more previous surgical interventions on the knee in question. * Preoperative flexion deformity greater than 10 degrees. * Presence of ligamentous injury which would require reconstruction, varus or valgus deformity requiring osteotomy, or cases that require complex surgery prior to cartilage regeneration