Chondral defects: genetic contribution and relevance and associations with pain, age, body mass index, joint surface area, cartilage volume and radiographic features of osteoarthritis

Abstract

The etiology and significance of nonfull thickness chondral defects is uncertain. This study had two objectives. Firstly, to describe the differences in chondral defect prevalence and severity between offspring of those with severe knee osteoarthritis (OA) and age-matched and sex-matched controls without this history and, secondly, using this population as a convenience sample, to describe the associations between chondral defects and pain, age, body mass index, joint surface area, cartilage volume and radiographic features of OA. We interviewed 372 male and female adults aged between 26 and 61 years (58% female, mean age 45 years). Of these, 50% had a parent who has severe knee OA requiring knee replacement and 50% were age-matched and sex-matched randomly selected controls. Chondral defects, cartilage volume and joint surface area was determined at the patella, medial and lateral tibial compartments of the right knee by quantitative magnetic resonance imaging. Anthropometric factors were measured while knee injury history, knee pain and occupation involving significant bending were assessed by questionnaire. Radiographic knee OA was assessed by semi-flexed AP views. Chondral defects were surprisingly common and were more prevalent and severe in the offspring (57% versus 43%, P = 0.007; defect score 5.7 versus 5.1, P = 0.002). This was independent of other factors with the exception of pain and joint surface area, suggesting these three factors are all linked. In addition, chondral defects at the patella and femoral but not tibial sites were associated with knee pain but not injury history. Defect prevalence and severity also increased with increasing age and body mass index, especially in females. Adjustment for radiographic features of OA decreased the magnitude of these associations, suggesting they are directly relevant to OA. Defect prevalence and severity also increased with osteophytes and increasing joint surface area and were associated with decreased joint space width and cartilage volume. Finally, knee cartilage defect severity was associated with a urinary marker of cartilage breakdown (r = +0.18, P < 0.001). In conclusion, knee cartilage defects are common, have a genetic component that is linked to the genetic contribution to knee pain and bone size, and may have a role in the genetic pathogenesis of knee OA. Furthermore, the associations between defects and OA risk factors, joint surface area and cartilage breakdown suggest that nonfull thickness defects in younger life may be a marker of OA risk in later life.