The infrapatellar fat pad is affected by injury induced inflammation in the rabbit knee: use of dexamethasone to mitigate damage

Outcome analysis of infrapatellar fat pad partial resection or preservation in patients with anterior cruciate ligament reconstruction

The infrapatellar fat pad (IPFP) is one of the structures surrounding the knee joint that obscures exposure in minimally arthroscopy anterior cruciate ligament reconstruction (ACLR). Most surgeons excise the partial fat pad for better exposure of the knee. However, whether removal of IPFP in ACLR remained inconclusive. The purpose of this study was to investigate clinical outcomes of IPFP preservation or resection in patients with primary hamstring-graft ACLR. A total of 104 patients were assigned to receive either IPFP-R (n = 55) or IPFP-P (n = 49). There were no significant preoperative differences between the two groups. The anterior knee pain (AKP) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) in the two groups both recovered compared with those at baseline, but the IPFP-P group recovered more significantly at 3-, 6-, 12-month, and 3-, 6-month of follow-up, respectively. When assessing the KOOS subclasses using minimum perceptible clinical improvement (MPCI), patients with IPFP-R failed to make significant improvement at 3 months in the symptoms, pain and sports subsets of the KOOS. Knee-related complications were not significantly different between the two groups, while the resection group had a higher incidence. These results suggested that ACLR with primary hamstring grafts can achieve good effects whether performed with IPFP resection or preservation; however, the improvements in anterior knee pain and knee joint functions are better for the patients with IPFP preservation. Therefore, surgeons should avoid the resection of IPFP as much as possible while fully exposing the wild view to ensure the ACLR.

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.

The Value of the Monocyte to High-Density Lipoprotein Cholesterol Ratio in Assessing the Severity of Knee Osteoarthritis: A Retrospective Single Center Cohort Study

Background

Inflammatory responses and metabolic abnormalities play essential roles in the pathophysiology of osteoarthritis (OA). Our study aimed to evaluate the association between monocyte-to-high density lipoprotein-cholesterol ratio (MHR) and OA and compared it with other systemic inflammatory markers.

Methods

This study recruited 323 OA cases and age- and sex-matched 283 control participants during the same period. Demographic, clinical, and imaging data and laboratory indicators were obtained from participants' records. Systemic inflammatory markers were calculated for both cohorts. The diagnostic effectiveness of each index for distinguishing patients with OA was analyzed using receiver operating characteristic (ROC) curves. Spearman's method and ordered logistic regression were used to analyze the association between each indicator and Kellgren and Lawrence (KL) grade.

Results

MHR was significantly higher (0.38±0.18 vs 0.25±0.07, p < 0.0001) in OA patients than healthy controls. MHR had the largest area under the ROC curve for predicting OA. Analysis of ordered logistic regression indicated that MHR was a risk factor for OA radiological severity. Spearman correlation analysis indicated that MHR significantly correlates with the KL grade. Moreover, MHR was significantly higher in early stage patients than in healthy controls.

Conclusion

These results suggest that an elevated MHR could reflect knee OA severity and might be a useful marker for diagnosis and monitoring of OA.

Osteoarthritis as an Umbrella Term for Different Subsets of Humans Undergoing Joint Degeneration: The Need to Address the Differences to Develop Effective Conservative Treatments and Prevention Strategies

Osteoarthritis (OA) of joints such as the knee and hip are very prevalent, and the number of individuals affected is expected to continue to rise. Currently, conservative treatments after OA diagnosis consist of a series of increasingly invasive interventions as the degeneration and pain increase, leading very often to joint replacement surgery. Most interventions are focused on alleviating pain, and there are no interventions currently available that stop and reverse OA-associated joint damage. For many decades OA was considered a disease of cartilage, but it is now considered a disease of the whole multi-tissue joint. As pain is the usual presenting symptom, for most patients, it is not known when the disease process was initiated and what the basis was for the initiation. The exception is post-traumatic OA which results from an overt injury to the joint that elevates the risk for OA development. This scenario leads to very long wait lists for joint replacement surgery in many jurisdictions. One aspect of why progress has been so slow in addressing the needs of patients is that OA has been used as an umbrella term that does not recognize that joint degeneration may arise from a variety of mechanistic causes that likely need separate analysis to identify interventions unique to each subtype (post-traumatic, metabolic, post-menopausal, growth and maturation associated). A second aspect of the slow pace of progress is that the bulk of research in the area is focused on post-traumatic OA (PTOA) in preclinical models that likely are not clearly relevant to human OA. That is, only ~12% of human OA is due to PTOA, but the bulk of studies investigate PTOA in rodents. Thus, much of the research community is failing the patient population affected by OA. A third aspect is that conservative treatment platforms are not specific to each OA subset, nor are they integrated into a coherent fashion for most patients. This review will discuss the literature relevant to the issues mentioned above and propose some of the directions that will be required going forward to enhance the impact of the research enterprise to affect patient outcomes.

α2-macroglobulin-rich serum as a master inhibitor of inflammatory factors attenuates cartilage degeneration in a mini pig model of osteoarthritis induced by “idealized” anterior cruciate ligament reconstruction

Post-traumatic osteoarthritis is a special type of osteoarthritis and a common disease, with few effective treatments available. α2-Macroglobulin (α2M) is important to chondral protection in post-traumatic osteoarthritis. However, its injection into xenogeneic joint cavities involves safety hazards, limiting clinical applications. Exploring serum α2M-enriching strategies and the therapeutic effect and mechanism of α2M-rich serum (α2MRS) autologous joint injection to treat post-traumatic osteoarthritis has significant value. In the present study, a unique filtration process was used to obtain α2MRS from human and mini pig serum. We evaluated the potential of α2MRS in protecting against post-surgery cartilage degeneration. We identify the potential of α2MRS in reducing the expression of inflammatory cytokines and factors that hasten cartilage degeneration in post-operative conditions leading to post-traumatic osteoarthritis. The potential of α2MRS was analyzed in interleukin-1β induced human chondrocytes and mini pig models. In the chondrocyte model, α2MRS significantly promoted human chondrocyte proliferation and reduced apoptosis and chondrocyte catabolic cytokine gene transcription and secretion. The anterior cruciate ligament autograft reconstruction model of mini pigs was randomized into groups, operated on, and injected with α2MRS or saline. The results showed that α2MRS injection significantly suppressed the levels of inflammatory factors, improved gait, and showed significantly lower cartilage degeneration than the groups that did not receive α2MRS injections. This study highlights the chondroprotective effects of α2MRS, elucidated its potential applications against cartilage degeneration, and could provide a basis for the clinical translation of α2MRS.

Perspective: Challenges Presented for Regeneration of Heterogeneous Musculoskeletal Tissues that Normally Develop in Unique Biomechanical Environments

Perspective: Musculoskeletal (MSK) tissues such as articular cartilage, menisci, tendons, and ligaments are often injured throughout life as a consequence of accidents. Joints can also become compromised due to the presence of inflammatory diseases such as rheumatoid arthritis. Thus, there is a need to develop regenerative approaches to address such injuries to heterogeneous tissues and ones that occur in heterogeneous environments. Such injuries can compromise both the biomechanical integrity and functional capability of these tissues. Thus, there are several challenges to overcome in order to enhance success of efforts to repair and regenerate damaged MSK tissues.

Challenges: 1. MSK tissues arise during development in very different biological and biomechanical environments. These early tissues serve as a template to address the biomechanical requirements evolving during growth and maturation towards skeletal maturity. Many of these tissues are heterogeneous and have transition points in their matrix. The heterogeneity of environments thus presents a challenge to replicate with regard to both the cells and the ECM. 2. Growth and maturation of musculoskeletal tissues occurs in the presence of anabolic mediators such as growth hormone and the IGF-1 family of proteins which decline with age and are low when there is a greater need for the repair and regeneration of injured or damaged tissues with advancing age. Thus, there is the challenge of re-creating an anabolic environment to enhance incorporation of implanted constructs. 3. The environments associated with injury or chronic degeneration of tissues are often catabolic or inflammatory. Thus, there is the challenge of creating a more favorable in vivo environment to facilitate the successful implantation of in vitro engineered constructs to regenerate damaged tissues.

Conclusions: The goal of regenerating MSK tissues has to be to meet not only the biological requirements (components and structure) but also the heterogeneity of function (biomechanics) in vivo. Furthermore, for many of these tissues, the regenerative approach has to overcome the site of injury being influenced by catabolism/inflammation. Attempts to date using both endogenous cells, exogenous cells and scaffolds of various types have been limited in achieving long term outcomes, but progress is being made.

Flexibility of infrapatellar fat pad affecting anterior knee pain 6 months after anterior cruciate ligament reconstruction with hamstring autograft

This study aimed to identify factors affecting anterior knee pain (AKP) after anterior cruciate ligament reconstruction (ACLR) with hamstring tendon autograft using ultrasonography. Forty-two patients were evaluated by ultrasound, 6 months after ACLR. The thickness of the superficial part of the infrapatellar fat pad was measured, as well as the thickness change ratio between the two angles. Color Doppler evaluated the rate of blood flow in the fat pad. AKP was assessed with the Kujala Scale. The correlations between AKP and age, body mass index, the thickness change ratio, and the grade of increased blood flow were examined. Independent variables showing significant correlations with AKP were used for multiple linear regression analysis. There were significant correlations between AKP and age (r = − 0.68), body mass index (r = − 0.37), the thickness change ratio of the fat pad (r = 0.73) and the grade of increased blood flow (r = − 0.42), respectively. Age and the thickness change ratio of the fat pad affected the AKP score (R² = 0.56). After ACLR, older age and a decrease in the thickness change ratio of the superficial area of the infrapatellar fat pad appear to affect post-operative AKP after 6 months.

Small extracellular vesicles from human adipose-derived stem cells attenuate cartilage degeneration

Osteoarthritis (OA) is a chronic degenerative disease of articular cartilage that is the most common joint disease worldwide. Mesenchymal stem cells (MSCs) have been the most extensively explored for the treatment of OA. Recently, it has been demonstrated that MSC-derived extracellular vesicles (EVs) may contribute to the potential mechanisms of MSC-based therapies. In this study, we investigated the therapeutic potential of human adipose-derived stem cells EVs (hASC-EVs) in alleviating OA, along with the mechanism. EVs were isolated from the culture supernatants of hASCs by a multi-filtration system based on the tangential flow filtration (TFF) system. The isolated EVs were characterised using dynamic light scattering (DLS), transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and flow cytometry analysis. The hASC-EVs not only promoted the proliferation and migration of human OA chondrocytes, but also maintained the chondrocyte matrix by increasing type Ⅱ collagen synthesis and decreasing MMP-1, MMP-3, MMP-13 and ADAMTS-5 expression in the presence of IL-1β in vitro. Intra-articular injection of hASC-EVs significantly attenuated OA progression and protected cartilage from degeneration in both the monosodium iodoacetate (MIA) rat and the surgical destabilisation of the medial meniscus (DMM) mouse models. In addition, administration of hASC-EVs inhibited the infiltration of M1 macrophages into the synovium. Overall results suggest that the hASC-EVs should be considered as a potential therapeutic approach in the treatment of OA.

Molecular Response of Rabbit Menisci to Surgically Induced Hemarthrosis and a Single Intra-Articular Dexamethasone Treatment

Anterior cruciate ligament reconstructive surgery can restore biomechanical stability, however, such surgery cannot reliably prevent the onset of post-traumatic osteoarthritis. The aim of this study was to elucidate the molecular response that occurs within the menisci following a surgical injury that allows bleeding into the joint space, and then to investigate the effect of dexamethasone (DEX) on this molecular response. Cell viability studies following acute controlled exposure to blood and blood plus DEX were also conducted. Forty-eight New Zealand white rabbits were randomly allocated into control, sham, surgical, and surgical  + DEX groups (each group n  =  6). Animals were sacrificed at 48 h and 9 weeks, and menisci were harvested. The messenger RNA (mRNA) expression levels for key inflammatory, and degradative proteins, as well as mRNA levels for autophagy pathway molecules were quantified, and statistically significant changes were described. Meniscal cell viability was calculated by incubating groups of medial and lateral menisci in autologous blood, or autologous blood plus DEX for 48 h (each group n  =  4; total of eight medial and eight lateral menisci), and then conducting a histological live/dead assay. Results indicated a significant reduction in only medial meniscal cell viability when the tissue was exposed to blood in combination with DEX. A single administration of DEX following surgery significantly suppresses the elevated molecular expression for key inflammatory and degradative markers within menisci at 48 h and 9 weeks post-surgery. In vitro, autologous blood did not affect cell viability, but addition of DEX uniquely impacted the medial menisci. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2043-2052, 2019.

Relationship between the deep flexion of the knee joint and the dynamics of the infrapatellar fat pad after anterior cruciate ligament reconstruction via ultrasonography

[Purpose] A sufficient flexion angle of the knee joint after knee surgery leads to higher quality of their life; therefore, here we investigated the relationship between the dynamics of the infrapatellar fat pad and seiza-style sitting via ultrasonography. [Participants and Methods] Twenty-eight patients were enrolled 3 months post-operatively after anterior cruciate reconstruction. They were divided into a “possible” group and “impossible” group, according to whether they could sit in the seiza style. The thickness of the superficial part of the infrapatellar fat pad was measured at 10° and 90° knee flexion on reconstructed knees in the sitting position via ultrasound evaluation. Images were taken to capture the patella apex and tibial tuberosity. The thickness of the superficial part of the infrapatellar fat pad was measured, and the thickness change ratio was calculated. The characteristics of each group were compared. [Results] The superficial part of the infrapatellar fat pad was significantly thinner in the possible group at a 10° knee flexion. The thickness change ratio of the infrapatellar fat pad was significantly greater in the possible group. [Conclusion] The thickness of the infrapatellar fat pad at a 10° knee flexion and the thickness change ratio of the infrapatellar fat pad could affect the possibility of sitting in the seiza style.

A Novel Rat Model of Patellofemoral Osteoarthritis Due to Patella Baja, or Low-Lying Patella

Background

Patella baja, or patella infera, consists of a low-lying patella that results in a limited range of motion, joint pain, and crepitations. Patellofemoral joint osteoarthritis (PFJOA) is a subtype OA of the knee. This study aimed to develop a reproducible and reliable rat model of PFJOA.

Material/Methods

Three-month-old female Sprague-Dawley rats (n=24) included a baseline group (n=8) that were euthanized at the beginning of the study. The sham group (n=8), and the patella ligament shortening (PLS) group (n=8) were euthanized and evaluated at ten weeks. The PLS model group (n=8) underwent insertion of a Kirschner wire under the patella tendon to induce patella baja. At ten weeks, the sham group and the PLS group were compared using X-ray imaging, macroscopic appearance, histology, immunohistochemistry, TUNEL staining for apoptosis, and micro-computed tomography (micro-CT). The patella height was determined using the modified Insall-Salvati (MIS) ratio.

Results

The establishment of the rat model of patella baja in the PLS group at ten weeks was confirmed by X-ray. In the PLS group, patella volume, sagittal length, and cross-sectional area were significantly increased compared with the sham group. The PFJ showed typical lesions of OA, confirmed macroscopically and histologically. Compared with the sham group, in the rat model of PFJOA, there was increased cell apoptosis, and immunohistochemistry showed increased expression of biomarkers of osteoarthritis, compared with the sham group.

Conclusions

A rat model of PFJOA was developed that was confirmed by changes in cartilage and subchondral bone.

Contribution of Infrapatellar Fat Pad and Synovial Membrane to Knee Osteoarthritis Pain

Osteoarthritis (OA) is the most common form of joint disease and a major cause of pain and disability in the adult population. Interestingly, there are patients with symptomatic OA displaying pain, while patients with asymptomatic OA that do not experience pain but show radiographic signs of joint damage. Pain is a complex experience integrating sensory, affective, and cognitive processes related to several peripheral and central nociceptive factors besides inflammation. During the last years, the role of infrapatellar fat pad (IFP), other than the synovial membrane, has been investigated as a potential source of pain in OA. Interestingly, new findings suggest that IFP and synovial membrane might act as a functional unit in OA pathogenesis and pain. The present review discuss the role of IFP and synovial membrane in the development of OA, with a particular focus on pain onset and the possible involved mediators that may play a role in OA pathology and pain mechanisms. Inflammation of IFP and synovial membrane may drive peripheral and central sensitization in KOA. Since sensitization is associated with pain severity in knee OA and may potentially contribute to the transition from acute to chronic, persistent pain in knee OA, preventing sensitization would be a potentially effective and novel means of preventing worsening of pain in knee OA.

Histopathological study of the infrapatellar fat pad in the rat model of patellar tendinopathy: A basic study

BACKGROUND

Patellar tendinopathy is difficult to successfully treat. This study aimed to characterize the pathological changes of the infrapatellar fat pad (IPFP) in patellar tendinopathy (PT), and to investigate the influence of PT on the development of fibrotic changes in the IPFP.

METHODS

Forty male Wistar rats were randomly divided into PT (n = 20) and control groups (n = 20). Bacterial collagenase I (patellar tendinopathy group) or saline (control) was injected, intratendinous, into the patellar tendon. Rats were sacrificed at week 12. The whole knee joint was sagittally sectioned and stained with hematoxylin-eosin and Masson's trichrome. The IPFP samples were graded according to cellularity, fibrosis, and vascularity. The whole IPFP and blue-stained area was measured. Mann-Whitney U tests were used to compare the between-group differences of each score and quantitative value.

RESULTS

Scores for cellularity were three (2-3) and 0 (0-1) in the PT and control groups, respectively (P < 0.01). Mean scores for fibrosis were two (1-3) and 0 (0-1) in the PT and control groups, respectively (P < 0.01). Mean scores for vascularity were two (2-3) and one (1-1) in the PT and control groups, respectively (P < 0.01). There was a significant difference in the total score between the PT and control groups (seven (5-8) and two (1-3), respectively) (P < 0.01). Average percentages of the fibrous area of the IPFP were 38.2 ± 26.5% and 11.2 ± 3.9% in the patellar tendinopathy and control groups, respectively (P < 0.01).

CONCLUSION

The IPFP in the patellar tendinopathy group showed greater cellularity, fibrosis, and vascularity than the control group.

Intra-articular injection of methylprednisolone for reducing pain in knee osteoarthritis: A systematic review and meta-analysis

BACKGROUND

To evaluate the efficacy and safety of intra-articular methylprednisolone for reducing pain in patients with knee osteoarthritis.

METHODS

We conduct electronic searches of Medline (1966-2017.11), PubMed (1966-2017.11), Embase (1980-2017.11), ScienceDirect (1985-2017.11), and the Cochrane Library (1900-2017.11) for randomized clinical trials comparing the use of methylprednisolone to treat knee osteoarthritis. The primary outcomes are Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain scores and WOMAC function scores. Each outcome was combined and calculated using the statistical software STATA 12.0. Fixed/random effect model was adopted based on the heterogeneity tested by I statistic.

RESULTS

A total of 739 patients were analyzed across 4 randomized controlled trials (RCTs). The present meta-analysis revealed that there were significant differences between groups regarding the WOMAC pain scores at 4 weeks (WMD = -1.384, 95% CI: -1.975 to -0.793, P = .000), 12 weeks (WMD = -1.587, 95% CI: -2.489 to -0.685, P = .001), and 24 weeks (WMD = -1.563, 95% CI: -2.245 to -0.881, P = .000). Significant differences were identified in terms of physical function at 4 weeks (WMD = -7.925, 95% CI: -13.359 to -2.491, P = .004), 12 weeks (WMD = -7.314, 95% CI: -13.308 to -1.320, P = .117), and 24 weeks (WMD = -6.484, 95% CI: -11.256 to -1.711, P = .008).

CONCLUSION

Intra-articular methylprednisolone injection was associated with an improved pain relief and physical function in patients with knee osteoarthritis. Additionally, no severe adverse effects were observed. Due to the limited quality of the evidence currently available, higher quality RCTs were required.

Role of low-grade inflammation in osteoarthritis

PURPOSE OF REVIEW

Inflammatory changes in joint tissues can be detected by modern imaging techniques in osteoarthritis patients, but may be clinically subtle compared with many other types of arthritis. These changes associate with disease progression and clinical severity, and many inflammatory mediators may have biomarker utility. Moreover, a number of inflammatory mechanisms play a role in animal models of disease, but it is still not clear which mechanisms predominate and might be therapeutically manipulated most effectively. This review highlights specific examples of recent advances published in the past 18 months that have advanced this field.

RECENT FINDINGS

Clinical investigators now show that synovial inflammation is associated with pain sensitization, and similar to knee osteoarthritis, is a common and important feature of hand osteoarthritis. In addition, recent advances in basic studies demonstrate inflammatory markers and mechanisms related to leukocyte activity, innate immune mechanisms, and the chondrocyte-intrinsic inflammatory response that might provide better opportunities for early detection, prognosis, or therapeutic intervention.

SUMMARY

Inflammation plays a central role in osteoarthritis pathogenesis, but additional translational work in this field is necessary, as are more clinical trials of anti-inflammatory approaches.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.