Infrapatellar fat pad in the knee: is local fat good or bad for knee osteoarthritis?

Abstract

IntroductionRecent studies regarding the infrapatellar fat pad (IPFP) mainly focus on the roles of the cells derived from the IPFP. There have been few clinical or epidemiological studies reporting on the association between the IPFP and knee osteoarthritis (OA). Our objective is to generate hypotheses regarding the associations between IPFP maximum area and knee OA measures in older adults.MethodsA total of 977 subjects between 50 and 80 years of age (mean, 62.4 years) participated in the study. Radiographic knee osteophyte and joint space narrowing (JSN) were assessed using the Osteoarthritis Research Society International atlas. T1- or T2-weighted fat suppressed magnetic resonance imaging (MRI) was utilized to assess IPFP maximum area, cartilage volume, cartilage defects, and bone marrow lesions (BMLs). Knee pain was assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire.ResultsAfter adjustment for potential confounders, IPFP maximum area was significantly associated with joint space narrowing (odds ratio (OR): 0.75, 95% confidence interval (CI): 0.62 to 0.91 (medial), 0.77, 95% CI: 0.62 to 0.96 (lateral)) and medial osteophytes (OR: 0.52, 95% CI: 0.35 to 0.76), knee tibial and patellar cartilage volume (β: 56.9 to 164.9 mm3/cm2, all P <0.001), tibial cartilage defects (OR: 0.58, 95% CI: 0.41 to 0.81 (medial), 0.53, 95% CI: 0.40-0.71 (lateral)), any BMLs (OR: 0.77, 95% CI: 0.63 to 0.94), and knee pain on a flat surface (OR: 0.79, 95% CI: 0.63 to 0.98). IPFP maximum area was negatively, but not significantly, associated with femoral cartilage defects, lateral tibiofemoral BMLs, and total knee pain or other knee pain subscales.ConclusionIPFP maximum area is beneficially associated with radiographic OA, MRI structural pathology and knee pain on a flat surface suggesting a protective role for IPFP possibly through shock absorption. Consequently, we must pay special attention to IPFP in the clinical settings, avoiding resection of normal IPFP in knee surgery.

Recent advances in the understanding of molecular mechanisms of cartilage degeneration, synovitis and subchondral bone changes in osteoarthritis

“…In addition, some local fat tissues, such as infra-patellar fat pad (IPFP), may act as modulators in OA. IPFP was considered a source of local inflammatory mediators and thus an active osteoarthritic tissue (144), but it also has a beneficial effect possibly through biomechanical mechanisms, as supported by a recent study suggesting that IPFP size was negatively associated with OA disease severity independent of BMI and total body fat (145).…”

Signal intensity alteration in the infrapatellar fat pad at baseline for the prediction of knee symptoms and structure in older adults: a cohort study

“…Participants (age 50–80 years) were selected and followed up over 2.7 years (range 2.6–3.3 years) as described previously 9 20. Institutionalised persons and subjects with contraindications to MRI and diagnosed rheumatoid arthritis were excluded.…”

“…Height and weight were measured as described previously 9 20. Body mass index (BMI, weight (kg)/height (m 2 )) was calculated.…”

“…A recent review paper suggested that it would play an important role in knee OA 8. Although the mechanisms of IPFP in pathological processes of knee OA are largely unknown, biomechanical and biochemical pathways may be involved 9 10. Biomechanically, IPFP may reduce the impact loading and absorb forces generated through the knee joint, and thus may play a beneficial role in knee OA.…”

Responsiveness of Infrapatellar Fat Pad Volume Change to Body Weight Loss or Gain: Data from the Osteoarthritis Initiative

“…The reliability of the measurement technologies used for this purpose has been reported previously Steidle-Kloc et al, 2016]. A methodological strength of the current study was that the IPFP was measured volumetrically (3-D) in addition to analyzing the IPFP area in a single 2-D slice as done in previous studies [Han et al, 2014;Pan et al, 2015;Teichtahl et al, 2015], because volumetric measures provide more information about IPFP morphology but also because the 3-D measures IPFP volume and depth showed statistically significant decreases in women with weight loss while no significant changes were observed in the 2-D slice with the largest IPFP area.…”