Rates of change and sensitivity to change in cartilage morphology in healthy knees and in knees with mild, moderate, and end-stage radiographic osteoarthritis: results from 831 participants from the Osteoarthritis Initiative.
OBJECTIVE
To study the longitudinal rate of (and sensitivity to) change of knee cartilage thickness across defined stages of radiographic osteoarthritis (OA), specifically healthy knees and knees with end-stage radiographic OA.


METHODS
One knee of 831 Osteoarthritis Initiative participants was examined: 112 healthy knees, without radiographic OA or risk factors for knee OA, and 719 radiographic OA knees (310 calculated Kellgren/Lawrence [K/L] grade 2, 300 calculated K/L grade 3, and 109 calculated K/L grade 4). Subregional change in thickness was assessed after segmentation of weight-bearing femorotibial cartilage at baseline and 1 year from coronal magnetic resonance imaging (MRI). Regional and ordered values (OVs) of change were compared by baseline radiographic OA status.


RESULTS
Healthy knees displayed small changes in plates and subregions (±0.7%; standardized response mean [SRM] ±0.15), with OVs being symmetrically distributed close to zero. In calculated K/L grade 2 knees, changes in cartilage thickness were small (<1%; minimal SRM -0.22) and not significantly different from healthy knees. Knees with calculated K/L grade 3 showed substantial loss of cartilage thickness (up to -2.5%; minimal SRM -0.35), with OV1 changes being significantly (P < 0.05) greater than those in healthy knees. Calculated K/L grade 4 knees displayed the largest rate of loss across radiographic OA grades (up to -3.9%; minimal SRM -0.51), with OV1 changes also significantly (P < 0.05) greater than in healthy knees.


CONCLUSIONS
MRI-based cartilage thickness showed high rates of loss in knees with moderate and end-stage radiographic OA, and small rates (indistinguishable from healthy knees) in mild radiographic OA. From the perspective of sensitivity to change, end-stage radiographic OA knees need not be excluded from longitudinal studies using MRI cartilage morphology as an end point.
Institute of Anatomy and Musculoskeletal Research, Paracelsus Medical University, Salzburg, Austria. felix.Eckstein@pmu.ac.at
Felix
F
Eckstein
Michael
M
Nevitt
Alberto
A
Gimona
Kristen
K
Picha
Jennifer H
JH
Lee
Richard Y
RY
Davies
Donatus
D
Dreher
Olivier
O
Benichou
Marie-Pierre Hellio
MP
Le Graverand
Martin
M
Hudelmaier
Susanne
S
Maschek
Wolfgang
W
Wirth
D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000473:pathology*; D016022:Case-Control Studies; D018450:Disease Progression; D005060:Europe; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011859:Radiography; D012720:Severity of Illness Index; D013997:Time Factors; D014481:United States