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Objective. Malalignment is known to alter medial-to-lateral femorotibial load distribution and to affect osteoarthritis (OA) progression in the mechanically stressed compartment. We investigated the pattern of cartilage loss in neutral, varus, and valgus knees. Methods. Alignment was measured from full-limb radiographs in 174 participants with symptomatic knee OA. Coronal magnetic resonance images were acquired at baseline and a mean SD of 26.6 5.4 months later. The weight-bearing femorotibial cartilages were segmented from paired images. Cartilage volume, surface area, and thickness were determined in total cartilage plates and defined subregions using proprietary software. Results. The medial-to-lateral ratio of femorotibial cartilage loss was 1.4:1 in neutral knees (n 74), 3.7:1 in varus knees (n 57), and 1:6.0 in valgus knees (n 43). The relative contribution of cartilage thickness change tended to be greater in knees with mild cartilage loss, whereas the increase of denuded area was greater in knees with accelerated cartilage loss. In both varus and neutral knees, the greatest changes were observed in the same subregions of the medial femorotibial compartment (central and external medial tibia, and central medial femur). In valgus and neutral knees, the subregions with the greatest changes in the lateral femorotibial compartment were also similar (internal and central lateral tibia, external lateral femur). Conclusion. The medial-to-lateral rate of femorotibial cartilage loss strongly depended on alignment. Subregions of greater-than-average cartilage loss within the stressed compartment were, however, similar in neutral, varus, and valgus knees. This indicates that the medial-to-lateral loading pattern is different, but that the (sub)regional loading pattern may not differ substantially between neutral and malaligned knees.

Objective Progressive knee osteoarthritis (OA) is believed to result from local factors acting in a systemic environment. Previous studies have not examined these factors concomitantly or compared quantitative and qualitative cartilage loss outcomes. The aim of this study was to test whether meniscal damage, meniscal extrusion, malalignment, and laxity each predicted tibiofemoral cartilage loss after controlling for the other factors. Methods Laxity and alignment were measured at baseline in individuals with knee OA. Magnetic resonance imaging included spin-echo coronal and sagittal imaging for meniscal scoring and axial and coronal spoiled gradient echo sequences with water excitation for cartilage quantification. Tibial and weight-bearing femoral condylar subchondral bone area and cartilage surface were segmented. Cartilage volume, denuded bone area, and cartilage thickness were quantified in each plate, with progression defined as cartilage loss >2 times the coefficient of variation for each plate. Qualitative outcome was assessed as worsening of the cartilage score. Logistic regression analysis with generalized estimating equations yielded odds ratios for each factor, adjusting for age, sex, body mass index, and the other factors. Results We studied 251 knees in 153 persons. After full adjustment, medial meniscal damage predicted medial tibial cartilage volume loss and tibial and femoral denuded bone increase, while varus malalignment predicted medial tibial cartilage volume and thickness loss and tibial and femoral denuded bone increase. Lateral meniscal damage predicted every lateral outcome. Laxity and meniscal extrusion had inconsistent effects. After full adjustment, no factor except medial laxity predicted qualitative outcome. Conclusion Using quantitative cartilage loss assessment, local factors that independently predicted tibial and femoral loss included medial meniscal damage and varus malalignment (medially) and lateral meniscal damage (laterally). A measurement of quantitative outcome was more sensitive at revealing these relationships than a qualitative approach.

Objective Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to examine the distribution of glycosaminoglycan in cartilage. This study sought to characterize dGEMRIC in the evaluation of knee osteoarthritis (OA) according to various radiographically determined disease parameters, and to examine the relationship between alignment of the knee joint and the lateral:medial dGEMRIC ratio. Methods Thirty-one patients with knee OA underwent MRI with a dGEMRIC protocol at 1.5T. Semiflexed knee radiographs and full-limb radiographs were also obtained for assessment of alignment. Results Compartments of the knee joint without joint space narrowing had a higher dGEMRIC index than those with any level of narrowing (mean 408 msec versus 365 msec; P = 0.001). In knees with 1 unnarrowed (spared) and 1 narrowed (diseased) compartment, the dGEMRIC index was greater in the spared versus the diseased compartment (mean 395 msec versus 369 msec; P = 0.001). In spared compartments, there was a trend toward a lower dGEMRIC index with increasing Kellgren/Lawrence (K/L) radiographic severity grade; the spared compartments of knees with a K/L grade 2 had a higher dGEMRIC index than those of knees with a K/L grade 4 (mean 425 msec versus 371 msec; P < 0.05). There was a range of dGEMRIC values in the spared compartments within a given K/L grade, demonstrating biochemical differentiation of disease in radiographically comparable compartments. Almost all compartments with narrowing had dGEMRIC indices of