Morphological characteristics of the infrapatellar fat pad

Echo intensity of the superficial part of the medial infrapatellar fat pad and medial meniscal extrusion are associated with knee symptoms in community-dwelling older adults

PURPOSE

Knee pain is a characteristic symptom of early-stage knee osteoarthritis. Recently, the association between knee symptoms and infrapatellar fat pad (IFP) degeneration has garnered attention. This study aimed to clarify the association between ultrasound-derived size and echo intensity (EI) in the IFP and knee symptoms.

METHODS

A total of 163 community-dwelling older individuals (women, n = 106; age, 75.1 ± 7.0 years) participated. An ultrasound imaging device was used to assess the area and EI of the superficial and deep parts of the central, medial, and lateral IFP and presence of medial meniscal extrusion (MME) and medial tibial osteophytes. Based on the 2011 version of the Knee Society Knee Scoring System (KSS) symptoms category, the participants were classified into a symptomatic (KSS symptom score < 23, n = 74) or asymptomatic (KSS symptom score ≧23, n = 89) group. Logistic regression analyses were performed with groups as dependent variables and EI and area of the IFP as independent variables.

RESULTS

EI of the superficial part of the medial IFP was significantly associated with knee symptoms, adjusting for age, sex, body mass index, MME, and medial osteophytes (p < 0.05). MME was also significantly associated with knee symptoms (p < 0.05). EI of the other parts, area of any parts, and medial osteophytes were not associated with knee symptoms.

CONCLUSION

These findings suggested the utility of evaluating EI on the superficial part of the medial IFP and MME as the articular structures associated with knee symptoms.

Research on the application effect of arthroscopic access modification in meniscal injury repair

OBJECTIVE

To investigate the application value of arthroscopic channel modification in meniscal injury repair.

METHODS

We retrospectively analyzed the data of 100 patients with meniscus injuries treated with knee arthroscopy from December 2022 to December 2023 and divided them into a control group and a modified group according to the application of "arthroscopic access modification technology". We compared the operation time, postoperative hospitalization time, VAS score, Lysholm knee function score, postoperative complications, and postoperative images of the patients in these two groups. We compared the operation time, postoperative hospitalization time, pre- and postoperative VAS scores, Lysholm knee function scores, postoperative complications and postoperative imaging indices of the patients in the two groups.

RESULTS

All patients successfully underwent surgery and were followed up without intraoperative vascular or nerve injury or postoperative complications such as infection, wound necrosis or thrombosis. The average follow-up time was 16.03 ± 3.69 months; the average operation time and postoperative hospitalization time of the modified group were significantly better than those of the control group were (P < 0.05); the pain and knee function of the two groups significantly improved over time (P < 0.05); and, compared with those of the control group, the modified group could obtain a more satisfactory score at an early stage of the postoperative period (P < 0.05), and the comparison of the intermediate and long-term scores of the two groups was not statistically significant (P > 0.05). There was no statistically significant difference (P > 0.05).

CONCLUSION

The improved arthroscopic access technique can make the entry and exit of instruments into and out of the joint cavity smoother, improve the surgical field of view, significantly shorten the operation time, reduce the occurrence of intraoperative complications, improve the function of patients' knee joints earlier, and increase their satisfaction with the operation.

Effects of High-intensity Continuous Ultrasound on Infrapatellar Fat Pad Stiffness and Gliding in Healthy Participants: A Randomized, Single-blind, Placebo-controlled Crossover Trial

OBJECTIVE

Ultrasound therapy effectively treats a joint range of motion limitation and pain originating from soft tissue in knee osteoarthritis (OA). Few interventional studies have focused on the infrapatellar fat pad (IFP), and the effects of high-intensity continuous ultrasound (HICUS) on IFP stiffness and gliding have not been investigated. Therefore, we aimed to determine the effects of HICUS on IFP stiffness and gliding.

METHODS

This single-blind, randomized, controlled crossover study involved 24 healthy participants. The HICUS and placebo conditions were applied to the knee joint on 2 different days. HICUS was performed (1 MHz, 2.5 W/cm², duty cycle 100%, 5 min) using an ultrasound machine equipped with an applicator and adsorption-type fixed automatic rotation irradiation function. The main outcomes were IFP stiffness and gliding measured at 10 degrees and 120 degrees knee flexion. Gliding was measured as the difference between the patellar-tendon tibial angles at 10 degrees and 120 degrees knee flexion. Measurements were performed before (T1), immediately after (T2), and 15 min after (T3) treatment.

RESULTS

Two-way repeated measures analysis of variance showed a significant interaction of IFP stiffness at 10 degrees knee flexion; post-test results showed that HICUS decreased stiffness at T2 and T3. There was no significant difference at 120 degrees. A significant interaction of gliding was observed under the HICUS condition. Post-tests showed that HICUS significantly improved gliding at T2 and T3.

CONCLUSION

HICUS is a simple, safe intervention for improving IFP stiffness and gliding in healthy participants, with sustained effects. Further studies are needed to evaluate its efficacy in patients.

Dynamic Changes in Muscle Thickness and Infrapatellar Fat Pad During Quadriceps Setting: An Ultrasound Echo Analysis

Purpose The infrapatellar fat pad (IFP) has the lowest pain threshold among all knee joint components and causes anterior knee pain after knee arthroplasty. It has been reported that selective muscle atrophy of the vastus medialis (VM) and fibrosis of the IFP may develop following knee joint surgery. Ultrasound enables visualization of IFP deformation (A1) from within the joint to the proximal area in response to muscle contraction, and this may be helpful in developing preventive and therapeutic strategies for IFP fibrosis. Therefore, this study aimed to clarify the relationship between quadriceps muscle thickness and dynamic changes in IFP during quadriceps setting (QS). Methods This study involved six participants (all men, 12 knees) with no history of knee joint problems, with a mean age of 36.7±8.7 years. We used ultrasound imaging to evaluate quadriceps muscle thickness and IFP dynamics. The muscle thicknesses of the VM, vastus lateralis (VL), vastus intermedius (VI) and rectus femoris (RF) were measured at rest and during QS with maximal contraction. The IFP measured the anterior-posterior width and the patellar tendon-tibia angle. The differences between conditions were examined using the Wilcoxon signed-rank test, and the correlation between the differences between measurement conditions was calculated using the Spearman rank correlation coefficient. Results The thickness of each muscle was measured and only the vastus lateralis muscle showed a significantly lower value during QS, while all other measurements showed higher values ​​(VM: p=0.0029, VL: p=0.0414, VI: p=0.0022, RF: p=0.0022, compared to resting). The mean anteroposterior width of the IFP increased by 0.9 mm medially (p=0.015) and 1.4 mm laterally (p=0.0076). Regarding the correlation between the measurements, a significant positive correlation was observed only between the VM difference and the lateral IFP difference (ρ=0.81, p=0.0071). Discussion The IFP provides a cushioning effect for the patellofemoral joint and reduces friction between the articular cartilage and the patellar ligament through functional deformation. In this study, a significant positive correlation was found between VM difference and lateral IFP difference. These findings suggest that the contractile force of the VM may be related to the extent by which the IFP is pushed outward, and changes in the flexibility of the soft tissues around the knee, such as IFP, may contribute to functional impairment in patients with knee joint disease. Conclusion This is the first study to quantitatively assess the extent of IFP deformation in the medial and lateral patella. The results of the study suggest that changes in soft tissue flexibility around the knee, such as in the IFP, may contribute to functional impairment in patients with knee joint disease.

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.

Morphological Changes in the Infrapatellar Fat Pad During Walking Detected by Dynamic Ultrasound in Healthy Volunteers

Aim This study aimed to verify specific morphological changes in the infrapatellar fat pad (IFP) during walking in healthy young participants. Methods A total of 17 healthy young participants (mean age, 22.8 ± 0.9 years) were recruited in this cross-sectional study. The IFP was evaluated using ultrasonography in three conditions: supine, standing, and walking. The IFP value was described as the thickness of the distal section of the IFP. Additionally, in the walking condition, the IFP was captured in video mode on ultrasonography, and its dynamics were recorded. The waveform of the IFP was produced using the sequence of the IFP thickness on each image. The morphological change of IFP (ΔIFP) was calculated in the IFP waveform and was shown as the difference in IFP thickness between the maximum and minimum at the beginning of the early stance phase. Moreover, kinematics and kinetic data were evaluated using a three-dimensional motion system, and the knee flexion angle (KFA) and knee flexion moment (KFM) were obtained. Results The thickness of the IFP during walking was significantly greater than that during the supine and standing conditions (p < 0.001 for both). The IFP waveform during walking showed a gradual increase during the stance phase and a decrease during the swing phase of the gait cycle. ΔIFP was 1.35 ± 0.42 mm and significantly correlated with the KFM (r = 0.59, p = 0.007). Conclusions Dynamic ultrasonography revealed a specific morphological change in the IFP during walking, which correlated with the KFM.

Advanced nanoparticles in osteoarthritis treatment

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, affecting hundreds of millions of people globally. Current clinical approaches are confined to providing only symptomatic relief. Research over the past two decades has established that OA is not merely a process of wear and tear of the articular cartilage but involves abnormal remodelling of all joint tissues. Although many new mechanisms of disease have been identified in the past several decades, the efficient and sustainable delivery of drugs targeting these mechanisms in joint tissues remains a major challenge. Nanoparticles recently emerged as favoured delivery vehicles in OA treatment, offering extended drug retention, enhanced drug targeting, and improved drug stability and solubility. In this review, we consider OA as a disease affecting the entire joint and initially explore the pathophysiology of OA across multiple joint tissues, including the articular cartilage, synovium, fat pad, bone, and meniscus. We then classify nanoparticles based on their composition and structure, such as lipids, polymers, inorganic materials, peptides/proteins, and extracellular vesicles. We summarise the recent advances in their use for treatment and diagnosis of OA. Finally, we discuss the current challenges and future directions in this field. In conclusion, nanoparticle-based nanosystems are promising carriers that advance OA treatment and diagnosis.

Profiling joint tissues at single-cell resolution: advances and insights

Advances in the profiling of human joint tissues at single-cell resolution have provided unique insights into the organization and function of these tissues in health and disease. Data generated by various single-cell technologies, including single-cell RNA sequencing and cytometry by time-of-flight, have identified the distinct subpopulations that constitute these tissues. These timely studies have provided the building blocks for the construction of single-cell atlases of joint tissues including cartilage, bone and synovium, leading to the identification of developmental trajectories, deciphering of crosstalk between cells and discovery of rare populations such as stem and progenitor cells. In addition, these studies have revealed unique pathogenetic populations that are potential therapeutic targets. The use of these approaches in synovial tissues has helped to identify how distinct cell subpopulations can orchestrate disease initiation and progression and be responsible for distinct pathological outcomes. Additionally, repair of tissues such as cartilage and meniscus remains an unmet medical need, and single-cell methodologies can be invaluable in providing a blueprint for both effective tissue-engineering strategies and therapeutic interventions for chronic joint diseases such as osteoarthritis and rheumatoid arthritis.