Prognostic factors associated with outcomes after knee cartilage repair across different procedure types: a systematic review.

PURPOSE: To identify and describe the prognostic factors associated with outcomes after knee cartilage repair within distinct procedure and disease contexts. METHODS: PubMed, Embase, the Cochrane Library, and Google Scholar were searched from inception to 29 August 2026; backward and forward citation searching was also performed. Eligible reports quantitatively evaluated baseline factor-postoperative outcome associations after knee cartilage repair. Two reviewers independently selected reports, extracted association-level data, and applied the quality in prognosis studies tool. Because effect measures could not be harmonized, findings were synthesized without meta-analysis by disease context, procedure, factor, outcome, and follow-up. RESULTS: Thirty-one reports were included, with report-level sample sizes totaling 13,022; cohort overlap prevented determination of the number of unique participants. Of 37 study-analysis units, 29 were at high risk-of-bias and 8 at moderate risk; none were at low risk. In isolated marrow stimulation, increasing age was associated with less favorable short- and long-term outcomes in two multivariable analyses at high overall risk-of-bias, whereas lesion-size findings varied across outcomes and follow-up. Autologous chondrocyte implantation (ACI)/matrix-induced autologous chondrocyte implantation (MACI) studies reported outcome-specific associations involving age, sex, body mass index, baseline status, defect characteristics, previous surgery, and manufacturing variables. Adjusted osteochondral-allograft failure analyses identified age, body mass index, diagnosis, graft area, and bony realignment as candidate factors; clinical-threshold and machine-learning findings remained context dependent. In osteoarthritis-associated cell-based cohorts, older age and bipolar lesions were associated with long-term failure in one adjusted analysis, while other findings were imprecise or derived from overlapping cohorts. No factor was consistently established across procedures or outcomes. A formal certainty-of-evidence framework was not applied because of marked heterogeneity, sparse context-specific evidence, and generally high risk-of-bias; definitive between-procedure comparisons were not possible. CONCLUSIONS: Available evidence identifies candidate prognostic associations within specific disease, procedure, outcome, and follow-up contexts. However, substantial clinical heterogeneity, potential confounding, cohort overlap, and sparse context-specific evidence limit the certainty and generalizability of the findings. The evidence does not support universal clinical cutoffs or conclusions that prognostic effects differ between procedures. LEVEL OF EVIDENCE: level IV, systematic review of level I-IV studies.