SPONTANEOUS CARTILAGE THICKENING IN OSTEOARTHRITIS KNEES: DATA FROM IMI-APPROACH AND THE OAI

INTRODUCTION

Articular cartilage was thought to have minimal repair capacity, but treatments like knee joint distraction show that regeneration is possible. Preliminary analyses have also suggested the possibility of spontaneous thickening of cartilage: thickening without external regenerative intervention.

OBJECTIVE

This study aims to evaluate spontaneous thickening in osteoarthritic knees.

METHODS

Patients from IMI-APPROACH and OAI cohorts were included. MRI-based mean medial and lateral cartilage thickness (ThCtAB; Chondrometrics) and knee radiographs were obtained at baseline, 1-year, and 2-year follow-up. Minimum medial and lateral joint space width (mJSW) and Kellgren-Lawrence grade (KLG) were automatically assessed from radiographs using KOALA (ImageBiopsy Lab). For each knee, mean whole-joint mJSW and ThCtAB changes over 2 years were calculated using linear regression. Knees were categorized as ‘thickening’ if both the mJSW and ThCtAB change were positive and as ‘thinning’ if both were negative; knees with inconsistent results were excluded. This approach was chosen because an increase in mJSW may reflect joint wedging or positional changes and increased ThCtAB may indicate swelling; especially in these expectedly relatively small changes, only an increase in both likely reflects true structural thickening.

Patient characteristics and two-year changes were compared using Mann-Whitney U and chi-square tests.

RESULTS

Out of 1,457 knees analyzed, 203 (14%) demonstrated thickening and 658 (45%) thinning. Patients with thickening were younger, predominantly female, had less pain and a lower KLG compared to those with thinning (all p<0.05). Over 2 years, knees with thickening received significantly fewer injections (p=0.043) and showed greater improvements in both mJSW and ThCtAB (both p<0.001). Complete results are presented in Table 1.

CONCLUSION

Spontaneous cartilage thickening can occur in osteoarthritic knees and is more prevalent in younger females with less severe joint damage. Future research is needed to determine whether this thickening (repair) potential can be predicted and may guide regenerative treatment options.