Abstract 561: Chondral Defects: Genetic contribution and relevance and associations with pain, age, body mass index, joint surface area, cartilage volume, and radiographic features of OA
Jones, Ding, Zhai, et al

This study evaluated the differences in chondral defects in the knee detected with MRI in subjects with a parent with knee OA compared to those without a parent with knee OA. The investigators then assessed relationships between these chondral defects and clinical variables.

Methods:This was a two part study. In the first, a population-based case-control study was designed in which 372 adults were evaluated of whom cases were defined as having a parent with severe knee OA requiring joint replacement. Controls were age and sex-matched with neither parent having TKR or symptomatic OA. Neither cases nor controls necessarily had OA themselves.

Quantitative MRIs were performed on the right knees and cartilage volume and area were assessed using T1 fat-suppressed imaging. Cartilage lesions were graded and scored. The subjects with chondral defects were then used as a convenience sample to evaluate associations between cartilage defects and clinical variables.

Results: Prevalent cartilage defects were seen in 57% of cases compared to only 43% of controls (p=0.002) with severity scores also higher in cases compared to controls. When these results were adjusted for knee pain and radiographic OA, however, the effect was decreased. This suggests a relationship between the presence of chondral defects and pain and radiographic OA.

Chondral defects were increased in prevalence and severity in older patients with higher BMI, similar variables associated with OA. These defects were also associated with osteophytes, cartilage volume, decreased joint space, decreased cartilage volume. Cartilage defect severity was also associated with urinary CTXII levels.

Editorial Comment: While there is an increase in the presence of chondral defects in subjects with a parent with OA, the fact that these differences are mitigated when adjusted for the presence of knee pain and radiographic OA suggests significant interplay between these variables. Other MRI findings were not discussed (e.g. synovitis or bone marrow lesions). The diagnoses of OA in the knee were based on historical information from the subjects about their parents and not validated against either radiographs of the parent or surgical diagnosis.

From the convenience sample, the investigators show that these chondral defects on MRI are associated with osteophytes, decreased joint space width, decreasing cartilage volume, and elevated levels of CTXII a marker of cartilage degradation. Further assessments of genetic and familial contributions with OA and MRI findings will require a more rigidly defined family study in which OA diagnosis and severity may be correlated in relatives. While the authors suggest that MRI chondral defects may precede the development of OA, this remains to be proven in a longitudinal study.

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