Healthy cartilage cells called chondrocytes can be harvested from a patient, grown in a lab, and transplanted back into the knee. The entire process takes about four to six weeks.
Since the patient donates his or her own chondrocytes, the procedure is called autologous chondrocyte implantation (ACI).
ACI is a fairly new procedure. Long-term studies are not available yet. Some of the earlier studies do show positive results. After having an ACI, symptoms improve. The patients report less pain and better function.
Activities of daily living are restored and quality of motion returns to normal. ACI clearly helps many patients who are in pain but do not have enough knee damage to need a total knee replacement.
At least one study followed patients for four years with good results. The main problem after ACI involves hypertrophy or overgrowth of tissue. Additional surgery may be needed after ACI to remove the excess tissue and smooth the surface over.