Associations Of Prefemoral And Quadriceps Fat Pads With Structural Changes And Symptoms In Knee Osteoarthritis

Peripatellar fat pads include prefemoral fat pad(PFP),quadriceps fat pad(QFP)and infrapatellar fat pad(IPFP).Previous studies have confirmed the role of IPFP in knee osteoarthritis(OA).Our study aimed to investigate the associations of PFP and QFP with structural changes and symptoms in knee OA.This study was divided into four chapters.The first chapter aimed to establish reliable magnetic resonance imaging(MRI)measures of PFP and QFP,and then verified their clinical relevance.In this chapter,we measured the quality changes and morphological characteristics of PFP and QFP,and tested agreements based on the measures of 30 knees.The results showed that their reliability evaluations met the international standard(>0.75).We analysed clinical associations of MRI measures in 708 knees,and found that PFP prefemoral hyperintensity alteration was associated with both scores of Kellgren-Lawrence Grading(KLG)and bone marrow lesion(BML)in medial tibiofemoral joint.PFP patellofemoral hyperintensity alteration was associated with The Western Ontario and McMaster Universities Arthritis Index(WOMAC)global score,Hoffa-synovitis,cartilage damage and BML of patellofemoral joint.PFP patellofemoral thickness was associated with KLG.QFP hyperintensity alteration and mass effects were associated with Hoffa-synovitis,and QFP maximum axial area was associated with BML of lateral tibiofemoral joint.The above results suggested that the novel method of MRI measures was reliable and clinically relevant.The second chapter aimed to investigate the associations between MRI measures of PFP and QFP and the occurrence of radiographic tibiofemoral OA within 4 years.This chapter involved a nested case-control study design that included 354 case knees and 354 control knees.Knee MRIs were read at P0(time of onset of incident radiographic tibiofemoral OA),P-1(1 year prior to P0),and BL(baseline).The results showed that PFP prefemoral hyperintensity alteration,PFP maximum axial area and QFP hyperintensity alteration,measured at three time points,were significantly associated with incident radiographic tibiofemoral OA.QFP mass effect measured at BL and P-1 were significantly associated with incident radiographic tibiofemoral OA.The above results suggested that PFP and QFP may be involved in the occurrence of radiographic tibiofemoral OA.The third chapter aimed to investigate the associations between MRI measures of PFP and QFP and structural changes in patellofemoral joint within 2 years.This chapter involved a traditionally longitudinal study design.A total of 708 knees were included at baseline,and 540 knees completed MRI follow-up in 2 years.The results showed that PFP prefemoral hyperintensity alteration,patellofemoral hyperintensity alteration,patellofemoral thickness and maximum axial area were associated with the presence of patellofemoral cartilage damage and BML,as well as the worsening in some measures(especially associated with lateral patellofemoral joint).MRI measures of QFP had no significant associations with the structural changes in patellofemoral joint.The above results suggested that PFP may be involved in the development or progression of the structural changes in the patellofemoral joint.The fourth chapter aimed to investigate the associations between MRI measures of PFP and QFP and the changes in knee OA symptoms within 2 years.This chapter involved a traditionally longitudinal study design.A total of 708 knees were included at baseline,and 692 knees completed the follow-up of WOMAC score in 2 years.The results showed that PFP patellofemoral hyperintensity alteration,patellofemoral thickness and QFP mass effect were associated with the presence of knee pain.PFP prefemoral hyperintensity alteration was associated with the presence of knee stiffness.This study found no associations of PFP and QFP with the worsening of knee OA symptoms within 2 years.The above results suggested that PFP and QFP might be involved in the development of knee OA symptoms.In summary,PFP and QFP were associated with both structural changes and symptoms of knee OA,suggesting that they are clinically relevant in knee OA.