Correlates of knee pain in younger subjects

The aim of this study was to describe clinical, structural and biochemical factors associated with knee pain in younger subjects. A cross-sectional convenience sample of 371 male and female subjects (mean age, 45 years, range 26–61) was studied. Knee pain was assessed by questionnaire. Chondral defects, cartilage volume, and bone area of the right knee were determined using T1-weighted fat saturation magnetic resonance imaging (MRI). X-ray was performed on the same knee for the assessment of radiographic features of osteoarthritis. The urinary C-terminal cross-linking telopeptide of type II collagen (CTX-II) was measured by enzyme-linked immunosorbent assay (ELISA). Height and weight were measured by standard protocols and body mass index (BMI) was calculated. The prevalence of knee pain was 35% in this sample. Chondral defect scores (particularly femoral and patellar but not tibial) were significantly associated with knee pain in a dose–response fashion (all p<0.01). Cartilage volume and bone area were not associated with knee pain in multivariate analysis in this sample. Urinary CTX-II was higher in subjects with knee pain (p=0.04), but this became nonsignificant after adjustment for BMI and osteophytes (both of which were significant) suggesting potential mechanisms of effect. In conclusion, knee pain is significantly associated with non-full thickness chondral defects (particularly femoral and patellar), osteophytes, CTX-II, and obesity but not other factors. MRI and biochemical measures can add to radiographs in defining unexplained knee pain in younger subjects.