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

The thickness change ratio and preservation ratio of the infrapatellar fat pad are related to anterior knee pain in patients following medial patellofemoral ligament reconstruction

BACKGROUND

The infrapatellar fat pad (IPFP) lies extrasynovial and intracapsular, preserving the joint cavity and serving as a biochemical regulator of inflammatory reactions. However, there is a lack of research on the relationship between anterior knee pain (AKP) and the IPFP after medial patellofemoral ligament reconstruction (MPFLR). Pinpointing the source of pain enables clinicians to promptly manage and intervene, facilitating personalized rehabilitation and improving patient prognosis.

METHODS

A total of 181 patients were included in the study. These patients were divided into the AKP group (n = 37) and the control group (n = 144). Clinical outcomes included three pain-related scores, Tegner activity score, patient satisfaction, etc. Imaging outcomes included the IPFP thickness, IPFP fibrosis, and the IPFP thickness change and preservation ratio. Multivariate analysis was used to determine the independent factors associated with AKP. Finally, the correlation between independent factors and three pain-related scores was analyzed to verify the results.

RESULTS

The control group had better postoperative pain-related scores and Tegner activity score than the AKP group (P < 0.01). The AKP group had lower IPFP thickness change ratio and preservation ratio (P < 0.001), and smaller IPFP thickness (P < 0.05). The multivariate analysis revealed that the IPFP thickness change ratio [OR = 0.895, P < 0.001] and the IPFP preservation ratio [OR = 0.389, P < 0.001] were independent factors related to AKP, with a significant correlation between these factors and pain-related scores [|r| > 0.50, P < 0.01].

CONCLUSIONS

This study showed the lower IPFP change ratio and preservation ratio may be independent factors associated with AKP after MPFLR. Early detection and targeted intervention of the underlying pain sources can pave the way for tailored rehabilitation programs and improved surgical outcomes. LEVEL OF EVIDENCE LEVEL III.

Ultrasound assessment of the infrapatellar fat pad can detect Hoffa-synovitis in patients following anterior cruciate ligament reconstruction: A pilot study

Introduction

Osteoarthritis (OA) commonly occurs following anterior cruciate ligament reconstruction (ACLR), affecting over 50 % of patients within 10-15 years post-ACLR. The Hoffa-synovitis of the infrapatellar fat pad (IPFP) has been implicated as a major contributor to OA pathogenesis. While MRI is typically used to evaluate the IPFP, it is cost-prohibitive for routine screening. This study aimed to validate ultrasound as an alternative for detecting IPFP Hoffa-synovitis in participants post-ACLR.

Methods

In this cross-sectional study, 15 participants (18-35 years, 1-5 years post-ACLR) underwent two imaging sessions separated by one week. First, a standardized bilateral anterior knee ultrasound assessment was used to examine IPFP echo-intensity. Second, MRI scans of both knees were graded by a board-certified musculoskeletal radiologist for Hoffa-synovitis according to the Anterior Cruciate Ligament Osteoarthritis Score grading system. IPFP echo-intensity were quantified on each ultrasound image, and a limb symmetry index (LSI) was calculated to assess between-limb differences. We used an independent t-test and Cohen's d effect sizes to compare IPFP echo-intensity LSI between people with and without MRI-confirmed Hoffa-synovitis.

Results

Four of the 15 participants (27 %) exhibited MRI-confirmed Hoffa-synovitis. Significantly higher IPFP echo-intensity LSI values were found in participants with Hoffa-synovitis (32.1 ± 12.1 %) compared to those without (10.5 ± 10.4 %), confirming the ultrasound's ability to distinguish between the two groups (t = -3.44; p = 0.004; d = 2.01).

Discussion

Ultrasound detects bilateral IPFP signal intensity alterations in participants post-ACLR with MRI-confirmed Hoffa-synovitis. This work should be seen as a proof-of-concept, and further validation in a larger, more diverse sample is essential for verifying these results.

Magnetic resonance imaging assessments for knee segmentation and their use in combination with machine/deep learning as predictors of early osteoarthritis diagnosis and prognosis

Knee osteoarthritis (OA) is a prevalent and disabling disease that can develop over decades. This disease is heterogeneous and involves structural changes in the whole joint, encompassing multiple tissue types. Detecting OA before the onset of irreversible changes is crucial for early management, and this could be achieved by allowing knee tissue visualization and quantifying their changes over time. Although some imaging modalities are available for knee structure assessment, magnetic resonance imaging (MRI) is preferred. This narrative review looks at existing literature, first on MRI-developed approaches for evaluating knee articular tissues, and second on prediction using machine/deep-learning-based methodologies and MRI as input or outcome for early OA diagnosis and prognosis. A substantial number of MRI methodologies have been developed to assess several knee tissues in a semi-quantitative and quantitative fashion using manual, semi-automated and fully automated systems. This dynamic field has grown substantially since the advent of machine/deep learning. Another active area is predictive modelling using machine/deep-learning methodologies enabling robust early OA diagnosis/prognosis. Moreover, incorporating MRI markers as input/outcome in such predictive models is important for a more accurate OA structural diagnosis/prognosis. The main limitation of their usage is the ability to move them in rheumatology practice. In conclusion, MRI knee tissue determination and quantification provide early indicators for individuals at high risk of developing this disease or for patient prognosis. Such assessment of knee tissues, combined with the development of models/tools from machine/deep learning using, in addition to other parameters, MRI markers for early diagnosis/prognosis, will maximize opportunities for individualized risk assessment for use in clinical practice permitting precision medicine. Future efforts should be made to integrate such prediction models into open access, allowing early disease management to prevent or delay the OA outcome.

Relationship between the change in infrapatellar fat pad thickness assessed using ultrasonography and anterior knee pain on squatting after anterior cruciate ligament reconstruction

PURPOSE

Anterior knee pain (AKP) may occur after anterior cruciate ligament (ACL) reconstruction. The present study investigated the relationship between the change in infrapatellar fat pad (IFP) thickness assessed using ultrasonography (US) and AKP on squatting in patients after ACL reconstruction.

METHODS

Patients were enrolled 3 months after ACL reconstruction using the bone-tendon-bone (BTB) technique. Subjects were divided into the AKP group (numerical rating scale [NRS] score ≥ 1) and control group (NRS score < 1) using a NRS of pain on squatting, and intergroup comparisons were performed. On US evaluation, measurement angles of the knee joint were 0° and 30° in the supine position. The IFP between the femoral intercondylar notch and patellar tendon was measured on short-axis images. The changes in IFP thickness were calculated from values measured at different angles of the knee joint.

RESULTS

Twenty-one patients (mean age 24.9 ± 9.3 years) were included in the present study: 12 in the AKP group (9 males, 3 females) and nine in the control group (5 males, 4 females). A significant difference in the change in IFP thickness at 3 months was observed between the AKP and control groups (0.67 ± 0.44 mm vs. 1.84 ± 0.34 mm, p < 0.001). There was a negative correlation between the change in IFP thickness and the NRS score (r = - 0.720, p < 0.001) in reconstructed knees.

CONCLUSION

A smaller change in IFP thickness assessed using US after ACL reconstruction was identified as a factor contributing to AKP on squatting.

An Open Debate on the Morphological Measurement Methodologies of the Infrapatellar Fat Pad to Determine Its Association with the Osteoarthritis Process

INTRODUCTION

Knee osteoarthritis (OA) is a disease affecting all the neighboring articular tissues including the infrapatellar fat pad (IPFP). Although not yet as widely studied as other tissues in the knee, the IPFP has been recognized to have important metabolic activities and is a key player in OA.

METHODS

In this commentary, we will briefly describe the different methodologies employed for the MRI morphological measurement of this tissue and depict the findings in regard to OA.

RESULTS

The morphology of this tissue, monitored mainly with the use of magnetic resonance imaging (MRI), demonstrates changes during OA. However, studies of the IPFP morphological alterations and their association with the OA process have shown conflicting results, including a detrimental or beneficial role or no role at all. Although many reasons could explain such mixed findings, one might be the different methodologies used for the MRI measurement of area, volume, or signal intensity. In addition, several techniques are also employed for measuring the volume and signal intensity. An additional level of complexity is related to the presence within the IPFP of two different types of signal intensities, hyper-intensity, and hypo-intensity.

CONCLUSION

A consensus of a procedure to measure the morphology of the IPFP is urgently needed to fully appreciate the role of this tissue in the pathology of OA, as well as its uses for clinical decision-making.