BACKGROUND:A variety of strategies have been employed for managing articular cartilage defects of the knee, including drilling and abrasion arthroplasty. These treatments are not always effective and when they are, the benefits may only be transitory. Unsuccessfully treated cartilage damage may progress to degenerative disease states and result in the need for a total knee replacement. In recent years the surgical implantation of healthy cartilage cells (autologous cartilage implantation [ACI] ) into damaged areas has been seen as an alternative option and is currently under investigation as a potential improvement over the current strategies for the management and treatment of articular cartilage defects. OBJECTIVES:To determine the effectiveness of ACI in patients with full thickness articular cartilage defects of the knee. SEARCH STRATEGY:We searched the Cochrane Musculoskeletal Injuries Group specialised register (May 2002), Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2002), MEDLINE (1966 to June Week 4 2001), CINAHL (1982 to July Week 2 2001), EMBASE (1980 to 2001 Week 27), SPORTDiscus (1949 to June 2001), Current Contents (1993 Week 26 to 2001 Week 30) and the National Research Register (Issue 2, May 2002). SELECTION CRITERIA:Randomised and quasi-randomised trials comparing ACI with any other type of treatment (including no treatment or placebo) for symptomatic cartilage defects of the medial or lateral femoral condyle, trochlea or patella. DATA COLLECTION AND ANALYSIS:Two independent reviewers applied the entry criteria to identified studies. MAIN RESULTS:No completed randomised controlled trials investigating this treatment were identified through the above searches. One possible trial has been placed in Studies Awaiting Assessment, awaiting translation of the full trial report. Ongoing trials currently underway will be incorporated in future updates of this review. REVIEWER'S CONCLUSIONS:No information is available from RCTs which can influence current practice. Therefore, since current evidence is subject to the inherent weaknesses of case series or reports, ACI must currently be considered as a technology under investigation whose effectiveness is yet to be determined in well designed and conducted clinical trials. The results of ongoing randomised clinical trials will help improve this situation.