Topographic Patterns of Cartilage Lesions in Knee Osteoarthritis

Objective: Treatments for articular cartilage lesions could benefit from characterization of lesion patterns and their progression to end-stage osteoarthritis. The objective of this study was to identify, quantitatively, topographic patterns of cartilage lesions in the human knee. Design: Photographs were taken of 127 unilateral distal femora (from 109 cadavers and 18 arthroplasty remnants) with full-thickness cartilage lesions. Using digital image analysis, the lesions were localized, and normalized lesion size was determined for the patellofemoral groove (PFG) and the lateral and medial femoral condyles (LFC and MFC, respectively). Samples were classified into patterns using cluster analysis of the lesion size at each compartment. For each pattern, maps showing the extent and frequency of lesions were created. Results: Four main patterns (a-d) were identified (each P < 0.001), with the lesion size varying from small (a) to large in distinct regions (b-d). Pattern b had a predominant lesion (23% area) in the MFC and smaller (< 3%) lesions elsewhere. Pattern c had predominant lesions in the LFC (19%) and MFC (10%). Pattern d had a predominant lesion in the PFG (15%) and smaller lesions in the MFC (6%) and LFC (2%). The subpatterns of a (a1-a3) had relatively small lesions, with similarity between a2 and b and between a3 and d. Conclusion: The present methods facilitated quantitative identification of distinct topographic patterns of full-thickness cartilage lesions, based on lesion size and location. These results have implications for stratifying osteoarthritis patients using precise quantitative methods and, with additional longitudinal data, targeting cartilage treatments.