Background/Purpose: Osteoarthritis (OA) is a disease of multifactorial origin with a modest but significant heritable effect for disease severity in the knee joint. The aim of this study was to describe radiographic osteoarthritis (ROA) progression and cartilage loss over 10 years in a midlife cohort at higher risk of osteoarthritis and community based controls.

Methods: 220 participants [mean age 45 (26-61); 57% female] were studied at baseline and ten years. Approximately half were the adult offspring of subjects who had a knee replacement performed for knee OA and the remaining were randomly selected controls that were initially matched for age and sex. Joint space narrowing (JSN) and osteophytes  on radiographs and cartilage volume (tibial, patella) on MRI were assessed using standard protocols. Negative binomial and linear regression were used to describe radiographic changes (expressed as difference in ratios (dr)) and cartilage loss (expressed as difference in means (dm)) respectively. Multivariable analyses were first adjusted for age, sex and the corresponding baseline measures (i.e. baseline cartilage volume for cartilage loss).Then the four baseline measures which were significantly different between offspring and controls (BMI, knee pain, cartilage defects and tibial bone area) were added to the model.

Results: In unadjusted analysis for radiographic changes, there was a significant difference between offspring and controls for changes in total ROA, medial JSN, total tibial, total femoral and total osteophyte scores (Table 1). The associations persisted after adjusting for age, sex, and corresponding baseline measures. However, with the exception of medial JSN, most of the other associations were markedly attenuated after adjustment for baseline pain, weight, cartilage defects and tibial bone area.

In unadjusted analysis for cartilage loss, offspring lost more cartilage at the medial tibial site only. This persisted after adjustment for age, sex, baseline cartilage volume and baseline differences.

Conclusion: The offspring of subjects having a total knee replacement have greater incidence of radiographic osteoarthritis (both joint space narrowing and osteophytes) and higher medial tibial cartilage loss over ten years. This is mediated, in part, by baseline differences in pain, weight, cartilage defects and tibial bone area and suggests this group could be a target for early prevention strategies. 

Table 1: Differences between offspring and controls

Bold denotes statistical significance

*Adjusted for age, sex, corresponding baseline measure and baseline differences(BMI, knee pain, cartilage defects and tibial bone area)

JSN(Joint Space Narrowing)

ROA(Radiographic Osteoarthritis)