Infrapatellar fat pad area is associated with reduced knee symptomatic and structural abnormalities in older adults

Purpose: To investigate cross-sectional and longitudinal associations between infrapatellar fat pad maximum area and knee osteoarthritic abnormalities in older adults. Methods: A cross-sectional sample of 970 randomly selected subjects (mean 63 years, 48% female) was studied at baseline and 407 followed up 2.7 years later. Radiographic knee osteophyte and joint space narrowing (JSN) were assessed using OARSI atlas. T1- or T2-weighted fat suppressed magnetic resonance imaging (MRI) was utilized to infrapatellar fat pad maximum area, cartilage volume, cartilage defect and bone marrow lesions (BMLs). Knee pain was assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire. Results: Infrapatellar fat pad maximum area was positively associated with age, height, weight, and negatively with female sex (all p<0.01 in multivariable analyses). After adjustments of age, sex, height, weight, disease status and/or knee radiographic features, infrapatellar fat pad maximum area was significantly associated with decreased joint space narrowing (OR: 0.74 to 0.78, p<0.02) and osteophytes (OR: 0.52, p<0.01), increased knee tibial and patellar cartilage volume (beta: 59 to 165 mm3/cm2, all P<0.001), decreased tibial cartilage defects (OR: 0.54 to 0.58, all p<0.01), decreased BMLs (OR: 0.77, p<0.01), and decreased knee pain (pain on flat surface, OR: 0.79, P<0.05; pain on stairs, OR: 0.84, p=0.06). Longitudinally, infrapatellar fat pad maximum area was significantly associated with less loss of cartilage volume (medial tibial, beta: 0.8% per cm2, p=0.01; lateral tibial, beta: 0.7% per cm2, p=0.019), and less increase in cartilage defects (medial tibiofemoral, OR: 0.65, p=0.003). Conclusions: Infrapatellar fat pad maximum area is associated with decreased knee pain, radiographic OA, BMLs, and less cartilage loss and defect progression/development, suggesting that infrapatellar fat pad may be protective against knee OA in older adults.