Infrapatellar Fat Pad Volume Research Articles

Quantitatively Measured Infrapatellar Fat Pad Signal Intensity Alteration is Associated with Joint Effusion-synovitis in Knee Osteoarthritis.

The objective of this study is to investigate whether quantitatively measured infrapatellar fat pad (IPFP) signal intensity alteration is associated with joint effusion-synovitis in people with knee osteoarthritis (OA) over two years. Among 255 knee OA patients, IPFP signal intensity alteration represented by four measurement parameters [standard deviation of IPFP signal intensity (IPFP sDev), upper quartile value of IPFP high signal intensity region (IPFP UQ (H)), ratio of IPFP high signal intensity region volume to whole IPFP volume (IPFP percentage (H)), and clustering factor of IPFP high signal intensity (IPFP clustering factor (H))] was measured quantitatively at baseline and two-year follow-up using magnetic resonance imaging (MRI). Effusion-synovitis of the suprapatellar pouch and other cavities were measured both quantitatively and semi-quantitatively as effusion-synovitis volume and effusion-synovitis score at baseline and two-year follow-up using MRI. Mixed effects models assessed the associations between IPFP signal intensity alteration and effusion-synovitis over two years. In multivariable analyses, all four parameters of IPFP signal intensity alteration were positively associated with total effusion-synovitis volume and effusion-synovitis volumes of the suprapatellar pouch and of other cavities over two years (all P＜0.05). They were also associated with the semi-quantitative measure of effusion-synovitis except for IPFP percentage (H) with effusion-synovitis in other cavities. Quantitatively measured IPFP signal intensity alteration is positively associated with joint effusion-synovitis in people with knee OA, suggesting that IPFP signal intensity alteration may contribute to effusion-synovitis and a coexistent pattern of these two imaging biomarkers could exist in knee OA patients.

Intravoxel Incoherent Motion Diffusion-Weighted MR Imaging Findings of Infrapatellar Fat Pad Signal Abnormalities: Comparison Between Symptomatic and Asymptomatic Knee Osteoarthritis

Infrapatellar fat pad (IPFP) proton density-weighted images (PdWI) hyperintense regions on MRI are an important imaging feature of knee osteoarthritis (KOA) and are thought to represent inflammation which may induce knee pain. The aim of the study was to compare the intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) findings of PdWI hyperintense regions of IPFP between symptomatic and asymptomatic KOA and to determine whether IVIM-DWI parameters can be used as an objective biomarker for symptomatic KOA. In total, 84 patients with symptomatic KOA, 43 asymptomatic KOA persons, and 30 healthy controls with MRI were retrospectively reviewed. Demographic, IPFP-synovitis, Western Ontario and McMaster Osteoarthritis Index (WOMAC) pain sub-score, IPFP volume and depth and quantitative parameters of IVIM-DWI were collected. The chi-square test, Binary logistic regression and receiver operating characteristic curve (ROC) analysis were used for diagnostic performance comparison. The IPFP volume and depth were statistically significant differences between the non-KOA and sKOA groups (p<0.05). The IPFP PdWI hyperintense regions demonstrated significantly higher values of D and D* in the symptomatic KOA compared to those in the asymptomatic KOA (1.51±0.47 vs. 1.73±0.40 for D and 19.24±6.44 vs. 27.09±9.75 for D*) (both p<0.05). Multivariate logistic regression analyses showed that Higher D and D* values of IPFP hyperintense region were significantly associated with higher risks of knee pain (OR: 1.97; 95% CI: 1.21-3.19; p=0.006 for D and OR: 1.24; 95% CI: 1.09-1.41; p=0.001 for D*). Sensitivity and specificity of D value for symptomatic KOA were 80.28% and 83.33%, with an AUC of 0.78 (0.68-0.86). D* value had the sensitivity with 92.96% and a specificity of 58.33%, with an AUC of 0.82 (0.73-0.89) for symptomatic KOA. IVIM-DWI can be used as an additional functional imaging technique to study IPFP with signal abnormalities on PdWI, and the D and D* values may have potential value to predict the symptom in mild-to-moderate KOA patients.

Efficacy and safety of GLucocorticoid injections into InfrapaTellar faT pad in patients with knee ostEoarthRitiS: protocol for the GLITTERS randomized controlled trial

BackgroundKnee osteoarthritis (OA) is a prevalent disabling disorder that involves changes in articular cartilage damage, subchondral bone remodeling, synovitis, and abnormal infrapatellar fat pad (IPFP). Due to the complicated etiology and numerous phenotypes of knee OA, limited improvement is achieved for treatments among knee OA patients with different phenotypes. Inflammatory OA phenotype is a typical knee OA phenotype, and individualized treatment targeting inflammation is a promising way to obtain an optimal therapeutic effect for people with inflammatory knee OA phenotype. Glucocorticoid is a traditional anti-inflammatory drug for knee OA, and intra-articular glucocorticoid injections are recommended clinically. However, emerging evidence has shown that repeated intra-articular glucocorticoid injections in the long term would induce cartilage loss. IPFP and its adjacent synovium are considered as the main source of inflammation in knee OA. This GLITTERS trial aims to investigate if a glucocorticoid injection into the IPFP is effective and safe over 12 weeks among knee OA patients with an inflammatory phenotype.MethodsGLITTERS is a multicenter, double-blinded, randomized, and placebo-controlled clinical trial among knee OA patients with both Hoffa-synovitis and effusion-synovitis. Sixty participants will be allocated randomly and equally to either the glucocorticoid group or the control group. Each group will receive an injection of glucocorticoid or saline into the IPFP with an intra-articular hyaluronic acid injection as a background treatment at baseline and be followed at 4, 8, and 12 weeks. The primary outcomes will be changes in knee pain on a visual analog scale and effusion-synovitis volume measured on magnetic resonance imaging (MRI). The secondary outcomes will be changes in the total score of Western Ontario and McMaster Universities Osteoarthritis Index score, MRI-detected Hoffa-synovitis score, quality of life, pain medication use, IPFP volume, and the incidence of adverse reactions. Data analyses based on the intention-to-treat principle will include mixed-effects regressions, Wilcoxon rank-sum tests, and chi-square tests (or Fisher’s exact test).DiscussionGLITTERS may provide high-quality evidence for the efficacy and safety of ultrasound-guided glucocorticoid injections into IPFP among people with inflammatory knee OA in a short term. The results of this trial are expected to provide a reliable reference for a longer-term risk–benefit profile of this treatment in the future.Trial registrationClinicalTrials.gov NCT05291650. Registered on 23 March 2022.

MAVRIC based T2 mapping assessment of infrapatellar fat pad scarring in patients with total knee arthroplasty.

The infrapatellar fat pad (IPFP) has been implicated as a source of postoperative knee pain. Imaging the IPFP is challenging in patients with total knee arthroplasty (TKA) due to metallic susceptibility artifact. Multi-Acquisition Variable-Resonance Image Combination (MAVRIC)-based T2 Mapping has been developed to mitigate this artifact and can generate quantitative T2 data. Objectives of this study were to (1) measure T2 values of the IPFP in patients with TKAs using a MAVRIC based T2 mapping technique and (2) determine if IPFP T2 values are related to the degree of fat pad scarring or clinical magnetic resonance imaging (MRI) findings. Twenty-eight subjects (10 males, 18 females, Age: 66 + 7.2 years [Mean ± standard deviations]) undergoing clinical MRIs were sequentially recruited. Morphological imaging and quantitative T2 mapping sequences were performed on a clinical 1.5 Tscanner. The morphologic images were graded for the presence and severity of fat pad scarring and clinical outcomes. T2 values were calculated in the total fat pad volume, a normal regions of interest (ROI), and an abnormal ROI. T2 values were shortened in the total IPFP volume (p = 0.001) and within abnormal regions (p = 0.003) in subjects with more severe IPFP scarring. The difference between T2 values in normal-abnormal regions was greater in subjects with severe versus no scarring (+1426.1%, p = 0.008). T2 values were elevated in patients with MRI findings of osteolysis (+32.3%, p = 0.02). These findings indicate that MAVRIC-based T2 Mapping may be used as a quantitative biomarker of postoperative IPFP scarring in individuals following TKA.

Exploring Anatomo-Morphometric Characteristics of Infrapatellar, Suprapatellar Fat Pad, and Knee Ligaments in Osteoarthritis Compared to Post-Traumatic Lesions.

Several studies have investigated cartilage degeneration and inflammatory subchondral bone and synovial membrane changes using magnetic resonance (MR) in osteoarthritis (OA) patients. Conversely, there is a paucity of data exploring the role of knee ligaments, infrapatellar fat pad (IFP), and suprapatellar fat pad (SFP) in knee OA compared to post-traumatic cohorts of patients. Therefore, the aim of this study was to analyze the volumetric and morphometric characteristics of the following joint tissues: IFP (volume, surface, depth, femoral and tibial arch lengths), SFP (volume, surface, oblique, antero–posterior, and cranio–caudal lengths), anterior (ACL) and posterior cruciate ligament (PCL) (volume, surface, and length), and patellar ligament (PL) (volume, surface, arc, depth, and length). Eighty-nine MR images were collected in the following three groups: (a) 32 patients with meniscal tears, (b) 29 patients with ACL rupture (ACLR), and (c) 28 patients affected by end-stage OA. Volume, surface, and length of both ACL and PCL were determined in groups a and c. A statistical decrease of IFP volume, surface, depth, femoral and tibial arch lengths was found in end-stage OA compared to patients with meniscal tear (p = 0.002, p = 0.008, p < 0.0001, p = 0.028 and p < 0.001, respectively) and patients with ACLR (p < 0.0001, p < 0.0001, p = 0.008 and p = 0.011, respectively). An increment of volume and surface SFP was observed in group b compared to both groups a and c, while no differences were found in oblique, antero–posterior, and cranio–caudal lengths of SFP among the groups. No statistical differences were highlighted comparing volume, surface, arc, and length of PL between the groups, while PL depth was observed to be decreased in end-OA patients compared with meniscal tear patients (p = 0.023). No statistical differences were observed comparing ACL and PCL lengths between patients undergoing meniscectomy and TKR. Our study confirms that IFP MR morphometric characteristics are different between controls and OA, supporting an important role of IFP in OA pathology and progression in accordance with previously published studies. In addition, PL depth changes seem to be associated with OA pathology. Multivariate analysis confirmed that OA patients had a smaller IFP compared to patients with meniscal tears, confirming its involvement in OA.

Morphological characteristics of the infrapatellar fat pad

The relationship between the morphological characteristics of the infrapatellar fat pad (IFP) and joint deformity has yet to be fully elucidated. Therefore, the purpose of this study was to clarify the morphological characteristics of the IFP and to identify the relationships between morphological characteristics of the IFP and degenerative grade of the articular surface of the patella. This investigation examined 41 legs from 25 Japanese cadavers. The IFP length, width, and volume were measured. It was categorized into three types: Type I, IFP proximal located on medial and lateral sides of the patella; Type II, the IFP proximal only located medially; and Type III, absence of the IFP proximal. Articular surfaces were graded as macroscopically intact or mildly altered (Grade I), moderately (Grade II), or severely (Grade III). Grade III was significantly more frequent than Grades I or II in Type III. IFP volume was significantly larger in Type I than in Types II or III. A negative correlation was found between the degenerative grade of the articular surface of the patella and IFP volume. It was suggested that a relationship between the degenerative grade of the articular surface of the patella and the IFP volume.

Increased signal intensity, not volume variation of infrapatellar fat pad in knee osteoarthritis: A cross-sectional study based on high-resolution magnetic resonance imaging.

Infrapatellar fat pad (IPFP) is regarded as an essential knee tissue involved in osteoarthritis (OA) for its potential structural-related or metabolism-related function. This cross-sectional study aims to identify which part is more related to OA. Patients with knee OA (n = 53) and healthy controls (n = 54) were prospectively recruited. Based on high-resolution magnetic resonance imaging with a slice thickness of only 0.35mm, IPFP structural-related parameters (volume and maximal area), metabolism-related parameter (signal), degeneration indicators, and patellar maltracking indicators (patellar translation, patellofemoral angle, and Insall-Salvati ratio) were measured. IPFP volume (maximal area, and signal) was compared between healthy controls and OA patients. The level of significance for all comparisons was set as .05. OA patients had higher IPFP signal (672.9 ± 136.9 vs 567.3 ± 63.6, p = .009), but no significant difference in IPFP volume or maximal area compared with healthy controls. In healthy controls, IPFP signal was positively associated with age (β = 1.481; 95% CI: 0.286-2.676; p = .018); IPFP maximal area was positively related to Insall-Salvati ratio (β = 0.001; 95% CI: 0.0003-0.0017; p = .039), but not associated with patellar translation and patellofemoral angle. In OA patients, IPFP signal was positively associated with cartilage loss (β = 0.005; 95% CI: 0.003-0.007; p = .013); no correlation between knee pain and IPFP volume or maximal area was observed. The metabolism-related function of IPFP, which can be reflected by the IPFP signal, might play a more critical role in OA progression than its structural function.

Why do obese patients with oa have more pain?

The prevalence of obesity, osteoarthritis (OA) and chronic pain are rising globally and are major contributors to a progressive decline in physical function and quality of life. There is an established positive association between obesity and chronic pain. While substantial evidence supports this association in individuals with OA, the reasons underlying it remain unclear, with considerable insights gained from studying the effects of weight loss. Research on the impact of obesity in OA has mainly focused on its effects on joint loads, joint alignment, changes on imaging and biomarkers, with fewer studies considering the mediating role of these aspects on symptomatic change. In addition to increased joint loads, obesity creates low-grade systemic inflammation and in local adipose tissues (e.g. infrapatellar fat pad (IFP)) via the proliferation of pro-inflammatory cytokines and adipokines. The generation of OA pain through mechanical and inflammatory stimuli is well established via the activation of nociceptors in most joint tissues. Pain is a hallmark of OA disease progression, ranging from intermittent mechanical pain with activity to constant pain, thought to be largely due to low-grade inflammation. In addition, it is known that a subset of individuals with OA will have altered nociceptive signalling, manifesting in peripheral or central sensitization of pain, a process potentially enhanced in obese individuals. Historically, study of the relationship between obesity and pain in people with OA has used BMI ≥30kg/m2 as an indicator of obesity. A dose-response relationship has been observed between BMI and pain severity. Studies report that weight loss of as little as 5%, achieved either naturally or surgically, results in joint pain reduction. However, BMI is limited as a marker of obesity as it does not account for type of adipose tissue (i.e. subcutaneous or visceral), its distribution (abdomen vs extremities), or type of mass (muscle vs fat). These limitations are important since adipose tissue is metabolically active, a storer of macrophages, producing and releasing pro-inflammatory cytokines and adipokines (e.g. TNF-α, IL-6, leptin, adiponectin). Cytokines and adipokines are known contributors to extracellular matrix degradation, a process that ultimately leads to joint space narrowing. Adipokines are prominent in serum and can be considered a central driver of inflammation, while some are found in synovial fluid or the IFP, presenting a mechanism for a local effect. Thus it is unclear if pain improvement after weight loss is due to lower joint loads, lower levels of inflammation or a combination of both. Complicating the issue further is the prescription of opioids, which is higher for those who are obese compared to non-obese individuals and can lead to opioid-induced hyperalgesia. Despite OA clinical guidelines opposing their use, rates of opioid consumption continue to be a problem. Studies from preclinical models investigating obesity, pain, and OA are limited, but have contributed to evidence supporting the role of systemic and local inflammation being associated with pain sensitization to thermal and mechanical stimuli. Most recently, the critical role of signaling from fat cells in the development of pain sensitization was highlighted in a study of mice models with lipodystrophy. Initially protected from pain sensitization, lipodystrophic mice with transplanted adipose tissue developed hyperalgesia and allodynia. Knowledge from clinical studies has progressed with use of more detailed measurements of obesity, such as the type of adiposity. Recent advances include evidence on the contribution of visceral or subcutaneous adiposity, measured by dual x-ray absorptiometry, to pain in people with knee OA, indicating that visceral but not subcutaneous fat is associated with worsening knee pain. These results which accounted for BMI, support the systemic effects of obesity on pain in OA and implicate visceral fat as a driver of pain. In addition, there has been further study of the presence of bone marrow lesions (BMLs) and synovitis/effusion, which have been associated with pain or sensitization, and these changes can be more severe in obese individuals. Conflicting evidence exists regarding changes in BMLs and improvement in pain after weight loss. Evidence for the mediating role of synovitis/effusion in pain improvement after weight loss is limited, indicating a non-significant indirect effect. However, combined evidence regarding changes in cytokines, IFP volume and pain severity in obese individuals suggest that further research into synovitis/effusion is warranted. Gaps and opportunities for expanding our understanding of the mechanisms underlying the relationship between obesity and pain in individuals with OA will be discussed.

Changes in Infrapatellar Fat Pad Volume 6 to 12 Months After Anterior Cruciate Ligament Reconstruction and Associations With Patient-Reported Knee Function.

Hypertrophy of the infrapatellar fat pad (IFP) in idiopathic knee osteoarthritis has been linked to deleterious synovial changes and joint pain related to mechanical tissue impingement. Yet little is known regarding the IFP's volumetric changes after anterior cruciate ligament reconstruction (ACLR). To examine changes in IFP volume between 6 and 12 months after ACLR and determine associations between patient-reported outcomes and IFP volume at each time point as well as the volume change over time. In a subset of individuals, we examined interlimb IFP volume differences 12 months post-ACLR. Prospective cohort study. Laboratory. We studied 26 participants (13 women, 13 men, age = 21.88 ± 3.58 years, body mass index = 23.82 ± 2.21 kg/m2) for our primary aims and 13 of those participants (8 women, 5 men, age = 21.15 ± 3.85 years, body mass index = 23.01 ± 2.01 kg/m2) for our exploratory aim. Using magnetic resonance imaging, we evaluated the IFP volume change between 6 and 12 months post-ACLR in the ACLR limb and between-limbs differences at 12 months in a subset of participants. International Knee Documentation Committee subjective knee evaluation (IKDC) scores were collected at 6-month and 12-month follow-ups, and associations between IFP volume and patient-reported outcomes were determined. The IFP volume in the ACLR limb increased from 6 months (19.67 ± 6.30 cm3) to 12 months (21.26 ± 6.91 cm3) post-ACLR. Greater increases of IFP volume between 6 and 12 months were significantly associated with better 6-month IKDC scores (r = .44, P = .03). The IFP volume was greater in the uninjured limb (22.71 ± 7.87 cm3) than in the ACLR limb (20.75 ± 9.03 cm3) 12 months post-ACLR. The IFP volume increased between 6 and 12 months post-ACLR; however, the IFP volume of the ACLR limb remained smaller than that of the uninjured limb at 12 months. In addition, those with better knee function 6 months post-ACLR demonstrated greater increases in IFP volume between 6 and 12 months post-ACLR. This suggests that greater IFP volumes may play a role in long-term joint health after ACLR.

Infrapatellar fat pad volume and Hoffa-synovitis after ACL reconstruction: Association with early osteoarthritis features and pain over 5 years.

Infrapatellar fat pad (IPFP) morphology and Hoffa-synovitis may be relevant to the development and progression of post-traumatic osteoarthritis (OA). We aimed to compare IPFP volume and Hoffa-synovitis in participants with anterior cruciate ligament reconstruction (ACLR) and uninjured controls, and to determine their association with prevalent and worsening early knee OA features and pain in participants post-ACLR. We assessed IPFP volume and Hoffa-synovitis from magnetic resonance imaging (MRI) in 111 participants 1-year post-ACLR and 20 uninjured controls. Patellofemoral and tibiofemoral cartilage and bone marrow lesions (BMLs) were assessed from MRIs at 1 and 5 years post-ACLR, and worsening defined as any longitudinal increase in lesion size/severity. IPFP volume and Hoffa-synovitis prevalence were compared between groups with analysis of covariance and χ 2 tests, respectively. Generalized linear models assessed the relation of IPFP volume and Hoffa-synovitis to prevalent and worsening features of OA and knee pain (Knee injury and Osteoarthritis Outcome Score-Pain Subscale, Anterior Knee Pain Scale). No significant between-group differences were observed in IPFP volume (ACLR 34.39 ± 7.29cm3 , Control 34.27 ± 7.56cm3 ) and Hoffa-synovitis (ACLR 61%, Control 80%). Greater IPFP volume at 1-year post-ACLR was associated with greater odds of patellofemoral BMLs at 1-year (odds ratio [OR] [95% confidence intervals]: 1.104 [1.016, 1.200]) and worsening tibiofemoral cartilage lesions at 5-year post-ACLR (OR: 1.234 [1.026, 1.483]). Hoffa-synovitis at 1-year post-ACLR was associated with greater odds of worsening patellofemoral BMLs at 5-year post-ACLR (OR: 7.465 [1.291, 43.169]). In conclusion, IPFP volume and Hoffa-synovitis prevalence are similar between individuals 1-year post-ACLR and controls. Greater IPFP volume and Hoffa-synovitis appear to be associated with the presence and worsening of some early OA features in those post-ACLR, but not pain.

Quantitative volume and dynamic contrast-enhanced MRI derived perfusion of the infrapatellar fat pad in patellofemoral pain.

Patellofemoral pain (PFP) is a common knee condition and possible precursor of knee osteoarthritis (OA). Inflammation, leading to an increased perfusion, or increased volume of the infrapatellar fat pad (IPFP) may induce knee pain. The aim of the study was to compare quantitative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters, as imaging biomarkers of inflammation, and volume of the IPFP between patients with PFP and controls and between patients with and without IPFP edema or joint effusion. Patients with PFP and healthy controls were included and underwent non-fat suppressed 3D fast-spoiled gradient-echo (FSPGR) and DCE-MRI. Image registration was applied to correct for motion. The IPFP was delineated on FSPGR using Horos software. Volume was calculated and quantitative perfusion parameters were extracted by fitting extended Tofts' pharmacokinetic model. Differences in volume and DCE-MRI parameters between patients and controls were tested by linear regression analyses. IPFP edema and effusion were analyzed identically. Forty-three controls and 35 PFP patients were included. Mean IPFP volume was 26.04 (4.18) mL in control subjects and 27.52 (5.37) mL in patients. Median Ktrans was 0.017 (0.016) min-1 in control subjects and 0.016 (0.020) min-1 in patients. None of the differences in volume and perfusion parameters were statistically significant. Knees with effusion showed a higher perfusion of the IPFP compared to knees without effusion in patients only. The IPFP has been implicated as source of knee pain, but higher DCE-MR blood perfusion, an imaging biomarker of inflammation, and larger volume are not associated with PFP. Patient's knees with effusion showed a higher perfusion, pointing towards inflammation.

Association of infra-patellar fat pad size with age and body weight in children and adolescents

BackgroundThe infra-patellar fat pad (IPFP) represents a potential mediator between obesity, low grade inflammation, and knee osteoarthritis via endocrine pathways. Yet, not only in adults, but also in childhood obesity negatively impacts knee structures. ObjectiveThe current study therefore investigated the sex-specific growth of the IPFP with age and body weight in healthy children and adolescents. Materials and MethodsThirty young healthy subjects (60% girls; age 4–17 years, body weight 14–90 kg in girls and 29–105 kg in boys; BMI 12.2–32.4 kg/m2) without magnetic resonance imaging (MRI) knee pathology were studied. The IPFP volume was determined from sagittal T-1 weighted and proton-density spectral attenuated inversion recovery MRIs. The primary analysis focused on the sex-specific IPFP volume/body weight ratio as dependent, and age as independent variable, using linear regression models. A secondary analytic focus was the slope of the age-dependence of IPFP volume, without normalization to body weight. ResultsThere was no statistically significant association of the IPFP volume/body weight ratio with age in girls (p = 0.57) or boys (p = 0.31), the R2 of ranging from −0.32 to 0.14. The ratio was greater in boys (0.54 ± 0.10 cm3/kg) than in girls (0.45 ± 0.07 cm3/kg) (p < 0.01). The IPFP volume increased by approx. 2 cm3 per annum in both girls and boys, without any indication of a non-linear relationship. ConclusionOur findings reveal that the ratio of the IPFP volume and body weight remains constant between age 4 and 17 in both normal weight girls and boys, and that the IPFP volume increases linearly with age throughout this period.

Partial resection of the infrapatellar fat pad during anterior cruciate ligament reconstruction has no effect on clinical outcomes including anterior knee pain.

Anterior knee pain (AKP) is a major complication that occurs after anterior cruciate ligament reconstruction (ACLR), even when hamstring tendon (HT) grafts are used. Damage to the infrapatellar fat pad (IPFP) during arthroscopy can cause AKP. The purpose of this study was to evaluate the influence of IPFP preservation on clinical outcomes, including AKP, in patients who underwent ACLR with HT autografts using the inside-out technique. Forty-two patients who underwent primary ACLR with HT autografts were prospectively assessed for 2years after surgery. They were randomly selected to undergo treatment with as much intercondylar IPFP preservation as possible or with intercondylar IPFP resection to confirm the ACL origin on the femoral and tibial sides, especially the femoral footprint in deep flexion of the knee joint. The total IPFP volume was calculated using sagittal MR images before and 6months after surgery. The patients completed a subjective knee score questionnaire and were assessed for patellar tendon tenderness and pain with the half-squat test or single-leg hop test at 6months and 2years postoperatively. There were no differences in the patient characteristics, including age, sex, BMI, time from injury to surgery, and meniscus tear. The difference in the total size of the IPFP preserved was significant (P = 0.004). However, there were no significant differences in the subjective knee scores. Moreover, there were no differences in the clinical assessment parameters between the IPFP preservation and resection groups. The size of the IPFP decreased more in the resection group than in the preservation group at 6months after surgery. However, partial IPFP resection, which was used to better visualize the origin of the ACL, had no effect on the clinical outcomes, including AKP. Level II.

Serum adipokines/related inflammatory factors and ratios as predictors of infrapatellar fat pad volume in osteoarthritis: Applying comprehensive machine learning approaches

Objective. The infrapatellar fat pad (IPFP) has been associated with knee osteoarthritis onset and progression. This study uses machine learning (ML) approaches to predict serum levels of some adipokines/related inflammatory factors and their ratios on knee IPFP volume of osteoarthritis patients.Methods. Serum and MRI were from the OAI at baseline. Variables comprised the 3 main osteoarthritis risk factors (age, gender, BMI), 6 adipokines, 3 inflammatory factors, and their 36 ratios. IPFP volume was assessed on MRI with a ML methodology. The best variables and models were identified in Total-cohort (n = 678), High-BMI (n = 341) and Low-BMI (n = 337), using a selection approach based on ML methods. Results. The best model for each group included three risk factors and adipsin/C-reactive protein combined for Total-cohort, adipsin/chemerin; High-BMI, chemerin/adiponectin HMW; and Low-BMI, interleukin-8. Gender separation improved the prediction (13–16%) compared to the BMI-based models. Reproducibility with osteoarthritis patients from a clinical trial was excellent (R: female 0.83, male 0.95). Pseudocodes based on gender were generated.Conclusion. This study demonstrates for the first time that the combination of the serum levels of adipokines/inflammatory factors and the three main risk factors of osteoarthritis could predict IPFP volume with high reproducibility, with the superior performance of the model accounting for gender separation.

An investigation of the anatomy of the infrapatellar fat pad and its possible involvement in anterior pain syndrome: a cadaveric study.

The infrapatellar fat pad (IFP) is an extrasynovial, intracapsular, adipose body occupying the space in the knee joint between the inferior border of the patella, the femoral condyles, tibial plateau and patellar tendon. Little is known about the anatomy and normal function of the IFP, but it has been suggested to play a role in the aetiology of Anterior knee pain syndrome, including that associated with osteoarthritis. Forty-three knees from 11 male and 15 female embalmed cadavers (mean age 84years; range 55-97years) were investigated. The cadavers were donated and the study performed in compliance with the provisions of the UK Human Tissue Act (2004). The quadriceps tendon and the medial and lateral patellar retinacula were dissected from the patella, which was then reflected antero-distally. The IFP was carefully excised and details of its morphology and attachments to components of the knee joint were recorded, together with the presence of articular surface pathology on the patella and femoral condyles. The principal novel findings of the current study were that 81% of IFPs were attached to the superior border of the patella by supero-medial extensions and 65% were attached by supero-lateral extensions; the supero-medial extensions were larger than the supero-lateral extensions. The superior extensions of the IFP were always attached anteriorly to the patellar retinacula and in four individuals the extensions formed a full loop around the superior border of the patella. The volume of IFPs with attachments to the superior border of the patella was significantly greater (p=.007) than those without, and the IFP was attached to the medial meniscus in significantly (p=.009) more knees with IFP attachment to the superior border of the patella than those without. All IFPs were attached to the medial anterior horn of the meniscus and the medial Kaplan's ligament. Ninety-seven percent were attached to the lateral anterior horn of the meniscus and 97% to the lateral Kaplan's ligament. The length of IFP attachment to the lateral meniscus was significantly longer (p=.004) than that to the medial meniscus. Ninety-seven per cent of IFPs were attached to the superior portion of the patellar tendon with the mean tendon attachment being 60%. Ninety-one percent of IFPs were attached to the inferior border of the patella. Significantly fewer knees with patellar (p=.001) and femoral (p=.002) articular surface osteophytes exhibited superior IFP extensions and these extensions were significantly shorter in knees with patellar (p=.000) and femoral (p=.006) osteophytes, compared with those without. The IFP was attached to the medial meniscus in significantly fewer knees with femoral (p=.050) and patellar (p=.023) osteophytes than those without. All IFPs not attached to the anterior horn of the lateral menisci, medial Kaplan's ligament, superior patella or inferior border of the patella, were in knees with articular surface osteophytes. This relationship between IFP morphology and knee joint pathology suggests a functional role for the IFP that requires further investigation.

Movement and volume of infrapatellar fat pad and knee kinematics during quasi-static knee extension at 30 and 0° flexion in young healthy individuals

IntroductionThe purpose of this study was to determine the changes in the shape and volume of the infrapatellar fat pad (IPFP) associated with knee flexion angle in young healthy individuals. MethodsYoung, healthy individuals without a history of knee injuries participated in this cross-sectional study. Behavior of the IPFP was quantified using three-dimensional (3D) models of the IPFP, patella, patellar tendon, femur, and tibia obtained from MRI taken at 0° and 30° flexion. The outcomes were movement and volume change of the IPFP, movement of the patella and the tibia, and change of the patellar tendon angle and length. ResultsThe anterior surface of the IPFP significantly moved anteriorly by 5.23 mm (p = .003) between 30° and 0°. Change in the volume of the IPFP was significantly increased or decreased in eight hyperoctants defined by the tibial coordinate system. The IPFP moved from the postero-supero hyperoctants to anterior hyperoctants. Significant correlations were observed between the IPFP and mobility of the patella, patellar tendon or tibia. ConclusionThe IPFP moves antero-inferiorly during quasi-static knee extension from 30 to 0° in young healthy individuals. Comparisons of IPFP behavior between the healthy and pathological knees may help us understand the role of IPFP and problems caused by IPFP contracture in future studies.

The relationship between patellofemoral arthritis and fat tissue volume, body mass index and popliteal artery intima-media thickness through 3T knee MRI

Background/aimEvaluating the relationship of patellar chondromalacia with obesity, infrapatellar fat pad (IFP) volume and popliteal artery intima-media thickness (IMT).Materials and methodsA total of 203 patients with different degree of patellar chondromalacia (103 male, 100 female) and 52 control subjects (19 male, 33 female) were included and grouped according to sex, age, body surface area (BSA), body mass index (BMI) and patellar chondromalacia classification. All measurements were completed with 3T magnetic resonance imaging (MRI). Articular cartilage and IFP volume were measured in saggital plane using double echo steady state (DESS) and DIXON sequences, respectively. Patellar cartilage damage was graded using modified outerbridge classification, and the relations among cartilage volume and BMI, BSA, IFP, IMT were statistically assessed.ResultsPopliteal artery IMT showed an independent association with the prevalence of cartilage defects and IFP volumes (P ˂ 0.001). There was an association between BMI and IFP volumes (P ˂ 0.001). However, no differences were observed between IFP volume and different chondromalacia groups. When IFP measurements were corrected using individual BMI and BSA values, a positive correlation was found between control and advanced chondromalacia groups (P ˂ 0.001).ConclusionThis study demonstrates the relationship among obesity, IMT and chondromalacia and highlights this potential circle to develop effective treatments and inhibit the progression of chondromalacia.

Association Between Quantitatively Measured Infrapatellar Fat Pad High Signal-Intensity Alteration and Magnetic Resonance Imaging-Assessed Progression of Knee Osteoarthritis.

To describe the cross-sectional and longitudinal associations between quantitative measures of infrapatellar fat pad (IPFP) signal-intensity alteration and knee structural abnormalities in patients with symptomatic knee osteoarthritis (OA). A total of 261 patients (mean ± SD age 63.0 ± 7.2 years) with symptomatic knee OA were selected from a randomized controlled trial with a follow-up of 2 years. IPFP signal-intensity alterations at baseline were quantitatively measured on T2-weighted fat-saturated magnetic resonance imaging using MATLAB. These quantitative measures included the SD of whole IPFP signal intensity measurement, the upper quartile value of high signal intensity (UQH ), the ratio of volume of high signal-intensity alteration to volume of whole IPFP (percentageH ), and the clustering effect of high signal intensity (clustering-factorH ). Cartilage volume and defects and bone marrow lesions (BMLs) were assessed using validated measures. Higher baseline SD of the IPFP, UQH , and clustering-factorH were associated with greater loss of tibial cartilage volume and larger increases in tibiofemoral cartilage defects over 2 years. Patients with high and medium tertiles of clustering-factorH had greater loss of cartilage volume per annum compared with those with a low tertile (for high 4.9%, for medium 4.6%, and for low 3.3% annually). Baseline percentageH and clustering-factorH were positively and significantly associated with increases in tibiofemoral BMLs over 2 years. Cross-sectional associations between IPFP measures and knee structures were similar but more consistent. Quantitative measures of increased signal intensity in the IPFP were associated with knee structural abnormalities in the tibiofemoral compartment, suggesting that these measurements could be used as an additional entry criterion to enrich studies for faster progressors of knee OA.

Volume change in infrapatellar fat pad is associated not with obesity but with cartilage degeneration.

Infrapatellar fat pad has been implicated in knee osteoarthritis. We examined whether infrapatellar fat pad volume is associated with quantitative cartilage changes using magnetic resonance imaging T1ρ mapping. Fifty-eight knees of knee pain patients (19 men, 39 women, mean age 57.0 [range 29-85] years) who were conservatively managed and had >1 T1ρ mapping images taken over time were evaluated. We used three slices from the medial femoral and tibial cartilage; areas showing T1ρ values <130 ms and >50 ms were designated as having cartilage degeneration. Cases were categorized into three groups: Improvement, No Change, and Deterioration. Fat-suppressed T2-weighted sagittal magnetic resonance images were used for measuring infrapatellar fat pad volume. Percent change in infrapatellar fat pad volume was -5.01 ± 5.66%, -2.06 ± 4.92%, and 0.05 ± 6.09% in the Improvement (n = 22), No Change (n = 22), and Deterioration (n = 14) groups, respectively, demonstrating significantly reduced infrapatellar fat pad volume in the Improvement group (p < 0.05). Multivariate regression analyses revealed that the percent change in infrapatellar fat pad volume significantly affected T1ρ change category independent of age, sex, follow-up period, baseline infrapatellar fat pad volume, and Kellgren-Lawrence grade. Infrapatellar fat pad volume and obesity or body weight change showed no correlation. Infrapatellar fat pad volume was reduced in patients with improved quantitative cartilage assessment on magnetic resonance imaging T1ρ mapping. This is the first study demonstrating associations between quantitative cartilage changes and infrapatellar fat pad morphological changes, suggesting a detrimental role of infrapatellar fat pad volume in articular cartilage degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Quantitative MRI analysis of infrapatellar and suprapatellar fat pads in normal controls, moderate and end-stage osteoarthritis

The aim of this study was to analyze the magnetic resonance imaging (MRI) volumetric and morphometric characteristics of the infrapatellar fat pad (IFP) and the suprapatellar fat pad (SFP) in normal controls, moderate and end-stage osteoarthritis (OA) patients. Forty-four MRI images of the three groups were collected: a) 17 patients undergoing meniscectomy with Outerbridge score 0 (control group); b) 15 patients undergoing meniscectomy with Outerbridge score 3/4 (moderate OA group); and c) 12 patients undergoing total knee replacement (end-stage OA group). Volume, depth, femoral and tibial arch lengths of IFP were quantified. The hypointense IFP signals were also scored. The SFP volume, oblique, antero-posterior and cranio-caudal lengths were determined. IFP and SFP characteristics were compared between groups. A decrease of IFP volume, depth, femoral, and tibial arch lengths in moderate and end-stage OA compared to controls were observed. A difference in IFP hypointense signal was found between groups. No differences were found in SFP characteristics between the groups. In controls and moderate OA patients, correlations were found among the different MRI characteristics of both IFP and SFP, while in the end-stage OA group correlations were found only in SFP. We evidenced differences of the IFP MRI morphometric characteristics between the groups analyzed, supporting an important role of IFP in OA pathology and progression. On the contrary, no differences were highlighted in SFP analysis suggesting that this fat pad is not clearly involved in OA, probably due to its peculiar localization and different function.