This is a phase III, randomised controlled trial of matrix-encapsulated chondrocyte implantation procedure compared to the microfracture procedure in the repair of symptomatic cartilage lesions of the knee. Eligible patients were asked for informed consent preoperatively and randomised for chondrocyte implantation of microfractures. Those patients allocated to the chondrocyte implantation group will be harvested at time of first arthroscopic procedure and concurrent lesions were treated, as meniscus repair, ligament reconstruction, or malalignment corrected. The patients allocated to microfracture will be treated at the time of the only arthroscopic procedure. Both groups will have the same rehabilitation program. Prospective clinical, radiographic and magnetic resonance imaging will be performed as main outcomes.

Inclusion Criteria:

• Patients with symptomatic single chondral lesions of the knee from 1 to 4 cm2.
• Signed patient informed consent.
• Agree to adhere to rehabilitation protocol.

Exclusion Criteria:

• Inflammatory arthritis, septic arthritis, gout, pseudogout, Paget's disease, ochronosis, acromegaly, hemochromatosis, tumors, collagen mutations.
• Total meniscectomy
• Malalignment
• Evidence of osteoarthritis