• degree of filling of the lesion by repair tissue at 12 months through delayed gadolinium enhanced magnetic resonance imaging of cartilage (dGEMRIC) [ Time Frame: 12 months ] [ Designated as safety issue: No ]
  
• repair tissue quality at 12 months [ Time Frame: 12 months ] [ Designated as safety issue: No ]
  

• Knee-related pain, stiffness and function at 12 months (WOMAC parts A, B, C) [ Time Frame: 12 months ] [ Designated as safety issue: No ]
  
• Frequency and severity of adverse events between study groups [ Time Frame: 12 months ] [ Designated as safety issue: Yes ]
  

Cartilage repair currently remains a problematic orthopedic concern with no effective solution. The development of new surgical techniques or therapies is critical in meeting this medical need.

This Canadian trial will be a pivotal protocol study, conducted as a randomized, controlled trial. A total of 80 subjects, 40 subjects in each of the two groups (BST-CarGel applied to a microfractured lesion or microfracture alone), will be enrolled in this study. The subjects and investigative medical staff will not be blinded to treatment due to the difference in surgical incision size. However, although the treatment will not be blinded, the primary effectiveness assessment will be blinded. The primary endpoint of this study will be cartilage repair at 12 months proved by demonstrating that BST-CarGel treatment effectively fills cartilage lesions with high quality cartilaginous tissue. The secondary endpoints will be pain, stiffness and function while other tertiary endpoints will include safety, quality-of-life (QOL), as well as macroscopic characterizations of tissue repair. The primary measure of this study will occur at 12 months, when imaging of repair tissue using magnetic resonance (MR) and associated analyses will compare tissue volume, quality and other anatomical variables. Radiographic evaluations will be blinded. Volunteer biopsies at 13 months may be obtained. Pain, stiffness, function and QOL will be assessed prior to treatment, and at 3, 6 and 12 months following treatment using self-administered validated scores (WOMAC and SF-36). In addition, subject safety will be assessed through a record of adverse events.

Inclusion Criteria:

• Between 18 and 55 years of age
• Focal articular cartilage lesion on the medial femoral condyle
• Grade 3 or 4 acute (traumatic) or chronic (degenerative) lesion
• Stable knee

Exclusion Criteria:

• Multiple lesions or kissing lesions
• Clinically relevant compartment malalignment (> 5 degrees)
• Undergone ligament treatments in the affected knee within 2 years prior to trial
• Inflammatory arthropathy, such as rheumatoid arthritis, systemic lupus, or active gout
• Previous surgical cartilage treatments in the affected knee in the last 12 months