Background The infrapatellar fat pad (IPFP) is a significant source of pro-inflammatory cytokines and may be related to knee pain. The study aim was to determine the association between knee symptoms and each of IPFP size from knee MRI and density from peripheral (p) QCT knee images in non-obese postmenopausal women. Methods Postmenopausal women 50-85 yrs old with a BMI < 30 kg/m 2 and variable knee pain completed proton-density-weighted MRI and pQCT scans of the knee (one slice at the level of each compartment), where the IPFP was contoured to yield volumes (for MRI), areas and density (for pQCT). Knee symptoms were evaluated using the ICOAP and KOOS questionnaires, and OARSI physical function tests. Multivariable linear regression examined how IPFP metrics relate to these outcomes, accounting for age, BMI, use of pain medications, and Kellgren Lawrence (KL) score (≥2 vs <2). Results Among 47 women (mean age: 61.2(8.82)yrs, BMI:22.5(3.2)kg/m 2 , KL score ≥2: 27.6%), a 1cm 2 smaller IPFP CSA from pQCT slices of the medial femoral compartment was associated with a 2.3% lower KOOS ADL score, a 4.7% higher ICOAP constant pain score, and a 3.9% higher ICOAP total pain score . A 1mg/cm 3 higher IPFP density from the pQCT slice of the lateral tibial compartment was associated with a 4.27% lower KOOS ADL score. Meanwhile, a 1cm 3 larger overall IPFP volume from MRI was associated with a 2% higher ICOAP intermittent pain score. Conclusions A denser and thinner IPFP cross-sectional area but larger overall volume - suggesting a long, dense and skinny phenotype - may be a correlate of having more knee pain in postmenopausal women.
Yazdankhah et al. (Mon,) studied this question.