Correlation between the Signal Intensity Alteration of Infrapatellar Fat Pad and Knee Osteoarthritis: A Retrospective, Cross-Sectional Study

Impact of infrapatellar fat pad injury severity on subsequent patellofemoral cartilage degeneration following acute ACL tear

Objective

The infrapatellar fat pad (IFP) is important in the homeostasis of the knee joint due to its structural and immune-modulating properties. This study investigates the relationship between IFP injury severity during acute Anterior Cruciate Ligament (ACL) tears, and the future development of Patellofemoral Compartment (PFC) chondrosis.

Methods

Adult participants aged 18-45 years old who were known to have first-time ACL tears between 01/01/2009 and 10/1/2022 were included. Patients with concomitant knee pathologies at the time of injury were excluded from the study. All participants received ACL reconstruction surgery and had follow-up MRIs conducted within two years postoperatively. Preoperative IFP edema levels were assessed alongside both pre-and postoperative PFC. We analyzed the relationship between the initial IFP edema and future PFC progression on subsequent MRI scans.

Results

A total of 69 participants were included in this study. No significant correlation was found between the severity of initial IFP injury and the initial presence of PFC chondrosis (r = -0.04, P = 0.61). However, a significant positive correlation was observed between the severity of initial IFP injury and the future progression of PFC chondrosis (r = 0.44, P < 0.001). Additionally, a significant difference in the progression of PFC chondrosis was noted when comparing grade 1 to grade 2 IFP injuries (P = 0.001). No significant difference in PFC chondrosis development was identified when comparing grade 2 to grade 3 IFP injuries (P = 0.72).

Conclusion

Our study underscores the potential role of the IFP in preserving cartilage homeostasis by establishing a link between the severity of IFP injury and the subsequent development of PFC following ACL injury.

Infrapatellar fat pad as a source of biomarkers and therapeutic target for knee osteoarthritis

BACKGROUND AND OBJECTIVE

Osteoarthritis (OA) is a multifactorial and highly prevalent disease in elderly adults; however, its pathogenesis, diagnosis, and treatment are unmet needs nowadays. Research efforts have focused on elucidating the molecular mechanisms involved in the pathogenesis, onset, and progression of OA to facilitate early detection and effective therapeutic approaches. Infrapatellar fat pad (IPFP) represents a promising novel source of OA biomarkers given that it is an active player in OA. This review aims to investigate the current literature regarding the potential of the IPFP as a source of diagnostic and prognostic biomarkers for OA as well as potential target for novel therapies.

METHODS

A literature search was conducted in the PubMed database in June 2024. We included cross-sectional and longitudinal studies based on IPFP from human OA patients, oriented in the identification of imaging, biochemical, and molecular biomarkers in the IPFP.

RESULTS

After screening and evaluation, we included a total of 61 studies. Most of the imaging publications (n = 47) on IPFP are based on magnetic resonance imaging (MRI) that revealed potential semiquantitative and quantitative imaging biomarkers linked to inflammation, fibrosis, pain, and joint degeneration imaging parameters. Biochemical and molecular studies (n = 14) pointed out an increase in interleukin-6 (IL-6), fatty acid-binding protein 4 (FABP4), adiponectin, and lysophosphatidylcholine (LysoPC) in the IPFP during OA progression.

CONCLUSIONS

Imaging, biochemical, and molecular studies indicate OA potential biomarkers in the IPFP related to inflammation, lipid dysregulation, and fibrosis. The combination of imaging and biochemical biomarkers could provide a better prediction of OA onset and the identification of OA progressors at an early stage. The IPFP study could also reveal potential therapeutic targets with the vision of better precision medicine.

Role of spinal MRI for pre-operative work up in patients with adolescent idiopathic scoliosis: a retrospective case study and narrative review

INTRODUCTION

There remains variability in the acquisition of whole-spine MRI prior to surgical correction in patients with adolescent idiopathic scoliosis (AIS). In this study, we take a retrospective look at the clinical impact of uniformly obtaining spinal MRI on all patients with a diagnosis of AIS.

METHODS

Three hundred thirty four patients with presumed AIS who underwent surgery between 2017 and 2022 were identified; 283 of these patients who were asymptomatic and had a preoperative MRI in the database were included. We investigated radiographic, demographic, and clinical risk factors for the presence of neural axis anomalies. Radiologists' reports were reviewed to determine the level of the conus medullaris and the presence of any intra-spinal dysraphisms. The utility of known risk factors for neural axis anomalies and the utility of MRI identifying anomalies on clinical decision-making, intra-operative neuromonitoring (IONM) alerts, and postoperative neurologic insult in asymptomatic AIS patients were investigated.

RESULTS

There were 283 patients with a mean age of 14.1 years, 67 males (22.6%) and 26 (9.2%) left-sided thoracic curves. MRI identified nine patients with central cord dilations, four patients with low cerebellar tonsils, four patients with Chiari Malformations, five patients with low-lying conus, one patient with a tethered cord, and five patients with arachnoid cysts. Six (2.1%) of the 283 patients underwent a neurosurgical intervention and 3 (50%) of the 6 went on to have IONM alerts. Eighteen (6.4%) of the 283 patients had IONM alerts and 5 (28%) of the 18 had neural axis anomalies. None of the patients with IONM alerts had a permanent neurologic deficit post-operatively.

CONCLUSION

In asymptomatic patients presumed to have AIS, 9.9% had a neuro-axis anomaly, 2.1% needed a neurosurgical intervention, and 6.4% of the patients had an IONM alert. We did not find known risk factors for identifying neural axis anomalies to have statistically significant application in asymptomatic AIS patients. Presence of neuroaxis anomalies increased the chance of having IONM alerts, however, we were unable to demonstrate if neurosurgical interventions in these patients with anomalies were preventative for IONM alerts or have statistically significant protection against clinical complications.

Grading of Cartilage Damage in Degenerative Knee Osteoarthritis Based on Quantitative Parameters of the Infrapatellar Fat Pad: A Cross-Sectional Study

PURPOSE

The aim of this research was to investigate the relationship between quantitative texture parameters and degenerative cartilage damage in knee osteoarthritis (KOA) by conducting a full-volume texture analysis of infrapatellar fat pad (IFP). In addition, this study also explored if the quantitative texture parameter models outperform semi-quantitative model in cartilage damage classification tasks.

MATERIALS AND METHODS

This retrospective study involved 202 patients who were diagnosed with KOA using imaging and clinical examinations. Texture parameters of the IFP were extracted from sagittal FSE PDWI fat-suppressed sequence images, and least absolute shrinkage and selection operator regression was used for feature selection. Spearman correlation analysis was conducted to assess the relationship between semi-quantitative parameter (Hoffa-synovitis score), quantitative parameters, and cartilage damage. Five multi-classification logistic regression models were developed to predict cartilage damage grade by using Hoffa-synovitis score, texture parameters, and clinical characteristics as independent variables. Subsequently, the performance of these models was compared.

RESULTS

Eight texture features were screened out in this study. Correlation analysis showed that Hoffa synovitis score, texture parameters, and cartilage damage grade were significantly correlated (all P < 0.05). The strongest correlation was found between Hoffa-synovitis score and cartilage damage, demonstrating a moderate positive relationship (r = 0.62). In terms of texture features, the Correlation parameter exhibited a moderate positive correlation with cartilage damage (r = 0.49), while other texture parameters had a slight positive correlation degree of positive or negative correlation. In the task of classifying cartilage damage, the model's macro-average area under the curve (AUC) only using the Hoffa-synovitis score was 0.73 (95% confidence interval (CI): 0.64, 0.83), while the model using only selected texture parameters achieved a macro-average AUC of 0.84 (95% CI: 0.68, 0.94). Furthermore, the model that combined texture parameters and clinical features also achieved a macro-average AUC of 0.84 (95% CI: 0.72, 0.94). By integrating the Hoffa-synovitis score, texture parameters, and clinical features, the model's macro-average AUC experienced a slight improvement to 0.85 (95% CI: 0.74, 0.93). Notably, the model combining only Hoffa-synovitis score and texture parameters had the best classification performance, with a macro-average AUC of 0.88 (95% CI: 77, 0.97). The performance of the 4 models incorporating texture parameters outperformed that of the Hoffa-synovitis score alone (all P < 0.05), however with no significant statistical difference observed among the 4 models (all P > 0.05).

CONCLUSIONS

There existed a correlation between the texture parameters of the infrapatellar fat IFP and cartilage damage in KOA. The models using texture parameters demonstrated better performance in classifying cartilage damage compared to the models using only semi-quantitative parameter. Thus, we can infer that texture parameters had the potential to be valuable imaging biomarkers for evaluating cartilage damage.

Relationships Between the Infrapatellar Fat Pad and Patellofemoral Joint Osteoarthritis Differ With Body Mass Index and Sex

The role of the infrapatellar fat pad (IPFP) in knee osteoarthritis is not understood. This study aimed to identify relationships between MRI-based signal abnormalities in the IPFP and measures of structural pathology and symptom severity in PFJOA, as well as investigate the influence of obesity and sex on these relationships. Seventy participants (ages 28-80) with isolated PFJOA underwent bilateral knee MRI scan acquisitions and completed the Knee Injury and Osteoarthritis Outcome Score (KOOS). MR images were scored for abnormal IPFP area and signal intensity, joint effusion, synovial proliferation, and patellar and trochlear cartilage damage. Repeated measures correlations were performed to assess associations between abnormal area and signal of IPFP and PFJOA pathology and KOOS, respectively. Associations were interrogated across weight-based groups based on BMI and sex-based groups. Between abnormal IPFP and PFJOA pathology, we observed no significant associations. Between abnormal IPFP and patient-reported outcomes, we observed weak to moderate significant negative associations between the size of the abnormal IPFP area and all KOOS subscales. In a sex-based analysis of IPFP and KOOS associations, we observed significant moderate negative correlations between IPFP and KOOS scores across all subcategories in female participants. In male participants, abnormal IPFP was not associated with KOOS scores. The IPFP is significantly related to PFJOA patient-reported pain and function, and this correlation is stronger in high-risk OA groups.

Patient-responsive protein biomarkers for cartilage degeneration and repair identified in the infrapatellar fat pad

OBJECTIVES

Cartilage defects (CDs) are regarded as early manifestation of osteoarthritis (OA). The infrapatellar fat pad (IPFP) is an important mediator in maintaining joint homeostasis, disease progression and tissue repair, with a crucial role of its secreted proteins. Here, we investigate the proteome of the IPFP in relation to clinical status and response to surgical treatment of CDs.

METHODS

In order to characterize the proteome of the IPFP, samples from a cohort of 53 patients who received surgical treatment for knee CDs were analyzed with label-free proteomics. Patients were divided based on validated outcome scores for pain and knee function, preoperatively and at 1-year postoperatively, and on MRI assessment of the defect severity, fibrosis and synovitis.

RESULTS

Specific proteins were differentially abundant in patients with MRI features and better clinical outcome after CD surgery, including a downregulation of cartilage intermediate layer protein 2 (CILP-2) and microsomal glutathione s-transferase 1 (MGST1), and an upregulation of aggrecan (ACAN), and proteoglycan 4 (PRG4). Pathways related to cell interaction, oxidation and matrix remodeling were altered.

CONCLUSION

Proteins in the IPFP that have a function in extracellular matrix, inflammation and immunomodulation were identified as potentially relevant markers for cartilage repair monitoring.

Effect of isometric quadriceps exercise on local microcirculation of the infrapatellar fat pad in female patients with knee osteoarthritis

OBJECTIVE

To elucidate the local microcirculation of the infrapatellar fat pad (IFP) in patients with knee osteoarthritis (KOA) by determining the changes in IFP hardness and hemoglobin concentration during isometric quadriceps exercise (IQE).

DESIGN

In this observational cross-sectional study, patients diagnosed with bilateral KOA were included in the KOA group (30 knees), healthy older adults in the control group (20 knees), and younger adults in the young group (20 knees). Ultrasonography was performed at rest and during IQE to measure IFP hardness based on shear wave velocity. Near-infrared spectroscopy was performed to measure oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (cHb) in the IFP before (Baseline), during (IQE task), and after IQE (Post). IFP hardness and O2Hb, HHb, and cHb concentration were analyzed using a linear mixed model for the groups and measurement points.

RESULTS

During IQE, IFP hardness changes were significantly less in the KOA group than in the other groups (KOA: 95 % confidence intervals (CIs) [-0.854, 0.028]; control: 95 % CI [-0.941, -0.341]; and young: 95 % CI [-2.305, -1.706]). In the KOA group, O2Hb concentration exhibited no significant changes at Post compared with Baseline; however, significant changes were observed in the other groups (KOA: 95 % CI [-1.176, 0.423]; control: 95 % CI [-1.452, -0.276]; and young: 95 % CI [-4.062, -2.102]).

CONCLUSIONS

During IQE, changes in hardness and hemoglobin concentration in the IFP were not significant in the KOA group, suggesting impaired local microcirculation of the IFP.

The biphasic role of the infrapatellar fat pad in osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. It is a whole organ disease characterized by cartilage degeneration and varying degrees of synovitis, involving pathological changes in all joint tissues, such as cartilage, subchondral bone, ligaments, meniscus, synovium, and infrapatellar fat pad (IPFP). IPFP is the largest adipose tissue structure in the knee joint and is composed of fat cells, immune cells and blood vessels. Moreover, IPFP is located close to the cartilage and bone surface so that it may reduce the impact of loading and absorb forces generated through the knee joint, and may have a protective role in joint health. IPFP has been shown to release various cytokines and adipokines that play pro-inflammatory and pro-catabolic roles in cartilage, promoting OA progression. Intra-articular injections of IPFP-derived mesenchymal stem cells and exosomes have been shown to reduce pain and prevent OA progression in patients with knee OA. Previous studies have shown that IPFP has a biphasic effect on OA progression. This article reviews the latest research progress of IPFP, discusses the role and mechanism of IPFP in OA, provide new intervention strategies for the treatment of OA. This article will also discuss the handling of IPFP during the procedure of total knee arthroplasty.

Knowledge mapping and bibliometric analysis of medical knee magnetic resonance imaging for knee osteoarthritis (2004-2023)

Objectives

Magnetic resonance imaging (MRI) is increasingly used to detect knee osteoarthritis (KOA). In this study, we aimed to systematically examine the global research status on the application of medical knee MRI in the treatment of KOA, analyze research hotspots, explore future trends, and present results in the form of a knowledge graph.

Methods

The Web of Science core database was searched for studies on medical knee MRI scans in patients with KOA between 2004 and 2023. CiteSpace, SCImago Graphica, and VOSviewer were used for the country, institution, journal, author, reference, and keyword analyses.

Results

A total of 2,904 articles were included. The United States and Europe are leading countries. Boston University is the main institution. Osteoarthritis and cartilage is the main magazine. The most frequently cocited article was "Radiological assessment of osteoarthrosis". Guermazi A was the author with the highest number of publications and total references. The keywords most closely linked to MRI and KOA were "cartilage", "pain", and "injury".

Conclusions

The application of medical knee MRI in KOA can be divided into the following parts: (1). MRI was used to assess the relationship between the characteristics of local tissue damage and pathological changes and clinical symptoms. (2).The risk factors of KOA were analyzed by MRI to determine the early diagnosis of KOA. (3). MRI was used to evaluate the efficacy of multiple interventions for KOA tissue damage (e.g., cartilage defects, bone marrow edema, bone marrow microfracture, and subchondral bone remodeling). Artificial intelligence, particularly deep learning, has become the focus of research on MRI applications for KOA.

Kinematics of the anterior interval in individuals with knee osteoarthritis

[Purpose] Abnormal anterior interval kinematics may be associated with knee pain and loss of knee motion. We investigated the anterior interval kinematics during passive knee extension in individuals with knee osteoarthritis (OA). [Participants and Methods] The anterior interval space was evaluated in 13 healthy knees (healthy group) and 11 knees with OA (knee OA group) at 30° and 15° knee flexion using ultrasonography. We measured the angle between the anterior tibia and patellar tendon, known as the patellar tendon-tibial angle (PTTA). [Results] The PTTA significantly increased as the angle of knee flexion decreased in the healthy group. In the knee OA group, the PTTA did not change significantly at 30° and 15° knee flexion. The knee OA group had a considerably higher PTTA at 30° knee flexion and a smaller amount of change in PTTA during knee angle changes than the healthy group. However, after adjusting for age and body mass index (BMI), no significant differences were observed between groups. [Conclusions] Differences in the anterior interval kinematics during knee motion between groups may be due to aging and high BMI. Further research is required to address most of the factors influencing these abnormalities.

Qualitative and Quantitative Measures in the Infrapatellar Fat Pad in Older Adults: Associations with Knee Pain, Radiographic Osteoarthritis, Kinematics, and Kinetics of the Knee

RATIONALE AND OBJECTIVES

The purpose of this study is to delineate cross-sectional associations between qualitative and quantitative measures of the infrapatellar fat pad (IPFP) and knee symptoms, structure, kinematics, and kinetics in older adults.

METHODS

Ninety eligible subjects (90 knees, mean age 54.0 years, 68.9% female) were examined at our center. We used T2-weighted fat-suppressed magnetic resonance imaging (MRI) to evaluate signal intensity alteration, maximum sagittal area, and depth of the IPFP. Symptomatic osteoarthritis (SOA) was a pain subscale score greater than 0 on the Western Ontario McMaster Osteoarthritis Index. A Kellgren-Lawrence grade ≥ 2 identified incident radiographic osteoarthritis (iROA). Three-dimensional gait data were employed to analyze knee joint kinematics and kinetics. Correlation and regression analyzes assessed associations between IPFP measurements and SOA, iROA, kinematics, and kinetics.

RESULTS

There were strong and positive associations between IPFP signal intensity alteration and both SOA and iROA in multivariable regression analyzes [OR (95% CI): 2.849 (1.440 to 5.636), 2.356 (1.236 to 4.492), respectively]. Conversely, a significant negative correlation was observed between IPFP maximum area and flexion angle [B (95%CI): - 1.557 (-2.549 to -0.564)]. Moreover, adjusting for covariates did not reveal any significant correlation between IPFP parameters and other indicators (P > 0.05, respectively).

CONCLUSION

IPFP signal intensity alteration and area were associated with knee clinical symptoms, structural abnormalities, and flexion angle in adults over 40, respectively. These findings suggest that IPFP may be a crucial imaging biomarker in early and middle knee osteoarthritis.

Global trends and hotspots in the application of platelet-rich plasma in knee osteoarthritis: A bibliometric analysis from 2008 to 2022

Platelet-rich plasma (PRP) injection therapy holds great promise in improving knee cartilage repair. This bibliometric analysis aimed to explore the research landscape in the application of PRP for knee osteoarthritis (KOA) over the last 15 years. All articles investigating PRP in the application of KOA were retrieved from the web of science core collection. Publications were analyzed using R software, VOS Viewer, CiteSpace, Microsoft Excel, and an online bibliometric platform (https://bibliometric.com/). A total of 815 articles were identified, 6 articles from 2010 had the highest average number of citations in the local database. Filardo G., Kon E., Cole B.J., Marcacci M., and Di Martino A. are the top 5 authors based on the H-index. The "American Journal Of Sports Medicine" is the most authoritative journal in the field of PRP application in KOA. The United States is the global leader in this field, with European countries playing a pivotal role in collaborative exchanges. Taipei Medical University is the most prolific institution and Shahid Beheshti University Medical Sciences in Iran the fastest-rising institution. The keywords "Hyaluronic Acid," "cartilage," "growth factors," "mesenchymal stem cells," "intra-articular injection," "pain," "inflammation," "double-blind," "management," "placebo," "stromal cells," "rheumatoid arthritis," and "pathology" appeared most frequently. "Exercise," "volume," and "physical-activity" are the latest hot topics. Future trends in this field include the standardization of injection components, injection sites, and injection methods, the modulation of useful or harmful growth factor receptor expression, sports management, and the validation of contraindications to PRP.