Bridging the Gap: Do Patient-Reported Outcome Measures Reflect Objective Knee Function After Cartilage Repair?

Background/Objectives: Focal cartilage defects of the knee are a common cause of pain and functional impairment. While several patient-reported outcome measures (PROMs) and objective scores have been developed to assess clinical knee status and functional impairment, the correlation between subjective PROMs and objective clinical findings after cartilage repair surgery remains unclear. A better understanding of this relationship could enhance the interpretation of registry data and improve clinical decision-making. Methods: This study analyzed 52 patients from the German Cartilage Registry (KnorpelRegister DGOU) who underwent cartilage repair surgery of the knee at a single orthopedic university center in Germany. All patients were re-evaluated in a standardized follow-up examination. PROMs from either the registry or the follow-up examination and objective findings, summarized using a modified objective International Cartilage Repair Society [ICRS] score, derived from the International Knee Documentation Committee (IKDC) 2000 knee examination form, were correlated using Spearman's rank correlation coefficient. Results: Moderate and statistically significant negative correlations were observed between the objective ICRS score and Knee Injury and Osteoarthritis Outcome Score (KOOS) Symptoms (ρ = -0.420, p = 0.005), KOOS Quality of Life (QoL) (ρ = -0.377, p = 0.013), and the subjective IKDC score (ρ = -0.305, p = 0.028) The subjective IKDC score (IKDC-Subjective Knee Form) was also moderately and significantly correlated with the objective ICRS score (ρ = -0.305, p = 0.028). Other KOOS subscales (Pain, Activities of Daily Living (ADL), Sport) did not show statistically significant correlations with the objective ICRS score. Conclusions: PROMs provide valuable insights into patients' perceived outcomes after cartilage repair surgery, but do not fully reflect objective functional recovery, underlining the importance of combining them with clinical assessments. Level of Evidence: III.