Objective

To explore whether baseline to 12-month followup change in femorotibial cartilage thickness differs between subjects who received a total knee arthroplasty (TKA) between 24 and 60 months from those without TKA (non-TKA).

Methods

In this prospective cohort study, 531 right knees from Osteoarthritis Initiative participants with definite radiographic knee osteoarthritis (Kellgren/Lawrence [K/L] grades 2-4) were studied. Segmentation was applied to coronal fast low-angle shot magnetic resonance images, to quantitatively determine cartilage thickness in 16 femorotibial subregions. Unadjusted P values (t-tests) and P values adjusted for age, baseline body mass index (BMI), K/L grade, and sex (generalized estimating equation models) were used to evaluate differences in longitudinal 1-year rates of cartilage thickness between TKAs and non-TKAs, with total knee arthroplasty status as fixed effect.

Results

Of the 531 participants (mean ± SD ages 63 ± 9 years, BMI 30 ± 4.8 kg/m(2)), 40 received a femorotibial TKA within 4 years. At baseline, TKAs had thinner medial and lateral femorotibial cartilage (-15%; P < 0.001) than non-TKAs. Longitudinal cartilage thickness change was significantly greater in TKAs than in non-TKAs in the total femorotibial joint (area under the curve [AUC] 0.64), the lateral compartment (AUC 0.66), both tibiae (AUC ≥ 0.61), and the first 9 (of 16) ordered values of subregion change (AUC 0.64-0.69). Discrimination was stronger for TKAs that occurred at 24 and 36 months (n = 18) than for those at 48 and 60 months (n = 22).

Conclusion

Knees with incident TKA displayed smaller baseline cartilage thickness and greater lateral as well as location-independent ordered value femorotibial cartilage loss than non-TKAs. Discrimination of cartilage loss was greater for TKAs occurring within 2 years after the measurement than for those occurring later.

Purpose

To assess whether magnetic resonance (MR) imaging-based cross-sectional measures of structural joint damage can be used to predict knee replacement during the following year.

Materials and methods

Participants were drawn from the Osteoarthritis Initiative, a longitudinal observational study that includes 4796 participants who have knee osteoarthritis or are at risk. The HIPAA-compliant protocol was approved by the institutional review boards of all participating centers, and written informed consent was obtained from all participants. During the 5 years of follow-up, 199 knees underwent knee replacement and were matched with 199 control knees that did not undergo knee replacement. Knees were matched according to radiographic disease stage and patient sex and age. All knees that underwent knee replacement and had MR images available from the year before surgery were included. MR images were assessed for cartilage damage, bone marrow lesions, meniscal damage, meniscal extrusion, synovitis, and effusion prior to reported knee replacement. Conditional logistic regression was applied to assess the risk of knee replacement. Analyses were performed on a compartmental and knee level.

Results

Participants had a mean age ± standard deviation of 64.2 years ± 8.4 (range, 47-82 years) and were predominantly women (232 of 398 participants, 58.3%). Risk for knee replacement was significantly increased for knees that exhibited two or more subregions with severe cartilage loss (odds ratio [OR], 16.5; 95% confidence interval [CI]: 3.96, 68.76), more than two subregions with bone marrow lesions (OR, 4.00; 95% CI: 1.75, 9.16), medial meniscal maceration (OR, 1.84; 95% CI: 1.13, 2.99), effusion (OR, 4.75; 95% CI: 2.55, 8.85), or synovitis (OR, 2.17; 95% CI: 1.33, 3.56), but not extrusion (OR, 1.00; 95% CI: 0.60,1.67), when compared with knees that did not exhibit these features as the reference standard.

Conclusion

Apart from meniscal extrusion, all features of tissue abnormalities at MR imaging were related to clinical prognosis and could be used to predict knee replacement in the following year.

Objective

To evaluate whether change in fixed-location measures of radiographic joint space width (JSW) and cartilage thickness by MRI predict knee replacement.

Methods

Knees replaced between 36 and 60 months' follow-up in the Osteoarthritis Initiative were each matched with one control by age, sex and radiographic status. Radiographic JSW was determined from fixed flexion radiographs and subregional femorotibial cartilage thickness from 3 T MRI. Changes between the annual visit before replacement (T0) and 2 years before T0 (T-2) were compared using conditional logistic regression.

Results

One hundred and nineteen knees from 102 participants (55.5 % women; age 64.2 ± 8.7 [mean ± SD] years) were studied. Fixed-location JSW change at 22.5 % from medial to lateral differed more between replaced and control knees (case-control [cc] OR = 1.57; 95 % CI: 1.23-2.01) than minimum medial JSW change (ccOR = 1.38; 95 % CI: 1.11-1.71). Medial femorotibial cartilage loss displayed discrimination similar to minimum JSW, and central tibial cartilage loss similar to fixed-location JSW. Location-independent thinning and thickening scores were elevated prior to knee replacement.

Conclusions

Discrimination of structural progression between knee pre-placement cases versus controls was stronger for fixed-location than minimum radiographic JSW. MRI displayed similar discrimination to radiography and suggested greater simultaneous cartilage thickening and loss prior to knee replacement.

Key points

• Fixed-location JSW predicts surgical knee replacement more strongly than minimum JSW. • MRI predicts knee replacement with similar accuracy to radiographic JSW. • MRI reveals greater cartilage thinning and thickening prior to knee replacement.