Inflammation and Temporomandibular Joint Derangement.

Temporomandibular disorders (TMD) are a common stomatognathic disease affecting all age groups. Patients with internal derangement (ID) or osteoarthritis (OA) of temporomandibular joint (TMJ) often have TMJ synovitis. When TMJ synovial membrane is damaged, many inflammatory cytokines are produced and secreted from TMJ synoviocytes to synovial fluid of TMJ. It has been widely reported that many kinds of biologic factors are produced from TMJ synoviocytes stimulated with interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. One of the major symptoms of TMD is pain of the TMJ. Many study groups have studied relations between the development of TMJ pain and biologic factors secreted into synovial fluid of TMJ. Here, we summarize previous reports trying to elucidate this correlation. On the other hand, it has been reported that a new molecular mechanism of IL-1beta secretion called inflammasome is involved in several diseases with sterile inflammation. Because TMJ synovitis with ID and OA of TMJ is also sterile inflammation, inflammasome may be involved in the development of TMJ synovial inflammation. This review describes some molecular mechanisms underlying inflammation in TMJ, especially in TMJ synovitis, which may be useful for the development of new therapies against TMD.

Quantitative magnetic resonance imaging assessment of lateral atlantoaxial joint meniscoid composition: a validation study.

PURPOSE: Lateral atlantoaxial (LAA) joint meniscoid composition may have clinical significance in patients following neck trauma. However, the existing method of radiologically assessing meniscoid composition has an inherent element of subjectivity, which could contribute to measurement variability. The present study sought to investigate the accuracy of two-point Dixon fat/water separation MRI as a quantitative assessment of LAA joint meniscoid composition. METHODS: Sixteen LAA joint meniscoids were excised from four cadavers (mean [SD] age 79.5 [3.7] years; one female) following cervical spine MRI (two-point Dixon, T1-weighted VIBE and T2-weighted SPACE sequences). Composition of LAA joint meniscoids was undertaken by (1) histological examination by light microscopy, (2) calculation of fat fraction by Dixon MRI (both in-phase/opposed-phase and fat/water methods), and (3) the existing method of considering VIBE and SPACE signal intensities. Analysis was performed using the kappa statistic with linear weighting. RESULTS: Microscopy revealed three, five, and eight meniscoids to be composed of adipose, fibroadipose, and fibrous tissues, respectively. Dixon sequence MRI classified 11 of these meniscoids correctly, with 'substantial' level of agreement (In-phase/Opp-phase kappa statistic = 0.78 [95% CI 0.38, 1.17]; fat/water kappa statistic = 0.72 [95% CI 0.32, 1.11]). Level of agreement between microscopy and the VIBE and SPACE method was 'slight' (kappa statistic = 0.02 [95% CI - 0.34, 0.38]). CONCLUSIONS: Findings suggest that Dixon fat/water separation MRI may have superior utility in the assessment of LAA joint meniscoid composition than the existing method of considering VIBE and SPACE signal intensities. These slides can be retrieved under Electronic Supplementary Material.

The infrapatellar fat pad and the synovial membrane: an anatomo-functional unit.

The infrapatellar pad, a fibro-adipose tissue with peculiar microscopic and mechanical features, is gaining wide attention in the field of rheumatological research. The purpose of this descriptive review is to summarize the most recent published evidence on the anatomic, physiologic and biomechanical inter-relationship between the infrapatellar fat pad and the knee synovial membrane. As an extrasynovial tissue, the infrapatellar fat pad does not directly interact with the articular cartilage; based on its location in close contact with the synovial membrane, and due to the metabolic properties of adipose tissue, it may influence the behavior of the synovial membrane. In fact, considering evidence of macroscopic and microscopic anatomy, the infrapatellar fat pad is the site of insertion of the infrapatellar and medial synovial plicae. Also biochemically, there is much evidence highlighting the interaction among these two structures; in the case of inflammation, the mutual interplay is ascribable to the release of pro-inflammatory mediators stimulating the proliferation of inflammatory cells and promoting tissue modifications in both. All these assumptions could support the emerging idea that the infrapatellar fat pad and the synovial membrane may be considered a morpho-functional unit.

Contrast-enhanced MRI findings of the knee in healthy children; establishing normal values.

OBJECTIVES: To define normative standards for the knee in healthy children using contrast-enhanced MRI, focusing on normal synovial membrane thickness. Secondly, presence of joint fluid and bone marrow oedema was evaluated. METHODS: For this study, children without disorders potentially resulting in (accompanying) arthritis were included. Patients underwent clinical assessments, followed by contrast-enhanced MRI. MRI features were evaluated in consensus using the Juvenile Arthritis MRI Scoring (JAMRIS) system. Additionally, the presence of joint fluid was evaluated. No cartilage lesions or bone abnormalities were observed. RESULTS: We included 57 healthy children. The overall mean thickness of the normal synovial membrane was 0.4 mm (min-max; 0.0-1.8mm). The synovium was thickest around the cruciate ligaments and retropatellar and suprapatellar regions. The mean overall diameter of the largest pocket of joint fluid was 2.8 mm (min-max; 0.9-8.0mm). Bone marrow changes were observed in three children (all in the apex patellae). CONCLUSIONS: The normal synovial membrane was maximally 1.8 mm thick, indicating that the JAMRIS cut-off value of 2 mm can be considered a valid measure for evaluating synovial hypertrophy. Some joint fluid and bone marrow changes suggestive of bone marrow oedema in the apex patellae can be seen in healthy children. KEY POINTS: • Knowledge on the normal synovial appearance using contrast-enhanced MR is lacking. • In healthy children, normal synovial membrane is maximally 1.8 mm thick. • Normal synovium is thickest around the cruciate ligaments, retropatellar and suprapatellar. • Bone marrow oedema in the apex patellae is seen in healthy children.

Arthroscopic approach and intra-articular anatomy of the dorsal and plantar synovial compartments of the bovine tarsocrural joint.

OBJECTIVE: To determine arthroscopic approaches to the dorsal and plantar synovial compartments of the tarsocrural joint in adult cattle, and to describe the arthroscopic intra-articular anatomy from each approach. STUDY DESIGN: Ex vivo study. ANIMALS: Fresh adult bovine cadavers (n = 7). METHODS: Two tarsocrural joint were injected with latex to determine arthroscopic portal locations and arthroscopy of the tarsocrural joint of 12 tarsi was performed. The dorsolateral approach was made through the large pouch located between the long digital extensor and peroneus longus tendons. The dorsomedial approach was made just medial to the common synovial sheath of the tibialis cranialis, peroneus tertius, and long digital extensor tendons. The plantarolateral and plantaromedial approaches were made lateral and medial to the tarsal tendon sheath, respectively. RESULTS: Each approach allowed visualization of the distal tibia articulating with the proximal trochlea of the talus. Consistently observed structures included the distal intermediate ridge of the tibia, and the medial and lateral trochlear ridges and trochlear groove of the talus. Lateral and medial malleoli were best assessed from dorsal approaches. From the lateral approaches evaluation of the abaxial surface of the lateral trochlear ridge allowed visualization of the fibulocalcaneal joint. From the plantar approaches additional observed structures included the coracoid process of the calcaneus, plantar trochlea of the talus, and plantar talotibial and talofibular ligaments. CONCLUSION: In cattle, the dorsolateral and plantarolateral approaches allowed for the best evaluation of the dorsal and plantar aspects of the tarsocrural joint, respectively.

The Infrapatellar Adipose Body: A Histotopographic Study.

The infrapatellar fat pad (IFP) can be regarded as a peculiar form of fibro-adipose tissue localized close to the synovial membrane and articular cartilage. The aims of the present study were to analyze the microscopic anatomy of the IFP through histological and ultrastructural methods, comparing it with that of the subcutaneous tissue of the abdomen and of the knee. Ten specimens of IFP were sampled from bodies of the Donation Program of the University of Padua without a history of osteoarthritis. The IFP consisted of white adipose tissue, of lobular type, with lobules delimited by thin connective septa. The IFP lobule areas were smaller (p < 0.05) and the interlobular septa were thicker (p > 0.05) than those of subcutaneous tissues of the abdomen, whereas the IFP lobule areas were larger (p < 0.05) and the interlobular septa were thinner than those of the subcutaneous tissue of the knee (p < 0.05). The IFP adipocytes present a mean area of 3,708 ± 976 µm2 with a large intercellular space, whereas the mean area of the abdominal tissues was greater (6,082 ± 628 µm2; p < 0.05). At scanning electron microscopy the IFP adipocytes were covered by thick fibrillary sheaths, creating a basket around the adipocytes. The structural characteristics of the IFP (lobular aspect of the adipose tissue, thickness of the septa with scarce elastic fibers) could act as a plastic portion aimed at the absorption of pressure variation during knee articular activity. The extensive distribution of nerves suggests a possible role of the IFP as a mechanoreceptor, corresponding to a tridimensional connective mesh working in the proprioceptive regulation of the activity of the knee joint.

Cricoarytenoid Articulation in Elderly Japanese With Special Reference to Morphology of the Synovial Tissue.

OBJECTIVE: To clarify composite fibers and cells in the synovial tissues of the cricoarytenoid joint (CA joint). METHODS: Routine histology and immunohistrochemistry using sagittal or nearly sagittal sections obtained from 18 elderly cadaveric specimens. RESULTS: The CA joint capsule was thin and contained few elastic fibers. A limited supportive ligament, namely, a thickened fascia of the posterior cricoarytenoid muscles, was sometimes evident on the lateral aspect of the CA joint. However, even in the weaker medial aspect of the joint, no marked destruction of the synovial tissues was found. The CA joint always contained synovial folds--a short medial fold and long lateral folds--but these contained no or few macrophages, lymphocytes, and blood capillaries. In 2 exceptional specimens showing inflammatory cell infiltration in the submucosal tissue of the larynx, the macrophage-rich area extended toward the capsule and medial synovial fold. CONCLUSIONS: The lateral aspect of the CA joint was likely to be supported mechanically by the muscle-associated tissues. Strong support of the arytenoid by muscles might reduce the degree of CA joint injury with age. However, some patients with hoarseness due to mucosal inflammation of the larynx might have accompanying synovitis and subsequent cartilage injury in the CA joint.

Synovial plicae of the knee joint: the role of advanced MRI.

Synovial plicae are normal anatomical structures of the knee that may become symptomatic. MRI is an established technique for evaluating the anatomy of the knee, and it is a valuable tool for detecting plicae because of its high resolution resulting in increased tissue characterisation. At MRI, knee plicae appear as low-signal-intensity structures of variable size and thickness, and they are better visualised at fluid-sensitive sequences with or without fat suppression. The combined use of clinical examination and MRI may also facilitate the diagnosis of fibrotic or inflamed plicae that may be symptomatic. Arthroscopy remains the gold standard for recognition and repair of knee plicae in cases of knee dysfunction.

The medial synovial fold of the posterior cruciate ligament: cadaveric investigation together with magnetic resonance imaging and histology.

OBJECTIVE: The purposes of our study were to analyze magnetic resonance imaging (MRI) and cadaveric findings concerning the medial synovial fold of the posterior cruciate ligament (PCL) and to classify the types of fold according to anatomic location. METHODS: Two musculoskeletal radiologists reviewed MR images of 17 cadaveric knees to classify the types of medial fold of the PCL by consensus. The MRI types were divided into 3 groups. In type A, there was no definitive medial fold; and in type B, inferior-short type, there was a small protrusion of the medial border. Type C, inferior-long type, had a long enough fold to exceed the imaginary line, which is connecting between the medial tibial condyle and posterolateral aspect of the medial femoral condyle. Correlations were sought between the findings derived from the MRI studies and cadaveric dissections. Histologic analyses of the medial fold were also performed. RESULTS: On MRI, the most common type of medial fold was type B (76.4%), followed by type C (11.8%) and type A (11.8%). In the cadaveric investigation, the medial folds of both types B and C were found to project into the medial femorotibial joint. Moreover, there was also a protruding medial fold at the superior aspect of the PCL in the A. Histologic examination of the medial folds revealed collagenous tissue surrounded by synovial cells. CONCLUSIONS: Medial folds of the PCL are normal synovial structures that can be seen by MRI and in cadaveric studies in a large proportion of the population.

Pathology of articular cartilage and synovial membrane from elbow joints with and without degenerative joint disease in domestic cats.

The elbow joint is one of the feline appendicular joints most commonly and severely affected by degenerative joint disease. The macroscopic and histopathological lesions of the elbow joints of 30 adult cats were evaluated immediately after euthanasia. Macroscopic evidence of degenerative joint disease was found in 22 of 30 cats (39 elbow joints) (73.33% cats; 65% elbow joints), and macroscopic cartilage erosion ranged from mild fibrillation to complete ulceration of the hyaline cartilage with exposure of the subchondral bone. Distribution of the lesions in the cartilage indicated the presence of medial compartment joint disease (most severe lesions located in the medial coronoid process of the ulna and medial humeral epicondyle). Synovitis scores were mild overall and correlated only weakly with macroscopic cartilage damage. Intra-articular osteochondral fragments either free or attached to the synovium were found in 10 joints. Macroscopic or histologic evidence of a fragmented coronoid process was not found even in those cases with intra-articular osteochondral fragments. Lesions observed in these animals are most consistent with synovial osteochondromatosis secondary to degenerative joint disease. The pathogenesis for the medial compartmentalization of these lesions has not been established, but a fragmented medial coronoid process or osteochondritis dissecans does not appear to play a role.

Elbow synovial fold syndrome.

OBJECTIVE: The purpose of this article is to review the embryologic development, anatomy, and histology of the synovial plicae of the elbow. The pathophysiologic features, clinical manifestations, imaging findings, and treatment of elbow synovial fold syndrome will also be reviewed. CONCLUSION: Elbow synovial fold syndrome is an uncommon entity that is often confused with lateral epicondylitis. Knowledge of the clinical and imaging diagnosis of this entity is essential for the appropriate management of patients.

The synovial fold of the distal tibiofibular joint: A morphometric study.

Impingement of the synovial fold of the distal tibiofibular joint (DTFJ) may contribute to the development of chronic ankle pain and disability after ankle inversion sprain. The morphology of the synovial fold of the DTFJ and recess is poorly understood. The purpose of this study was to describe and quantify the synovial fold and recess of the DTFJ. Thirty-three pairs of adult embalmed ankle joints were dissected and the presence, disposition, morphology, and dimensions of the synovial fold were determined in relation to the DTFJ and its recess. A synovial fold was present in all specimens examined and extended from the deep posterior tibiofibular ligament along the DTFJ line an average of 15.31 mm [standard deviation (SD), 4.42 mm]. The majority of synovial folds were elongated in shape with smooth borders and occupied more than two thirds of the DTFJ line. In 70% of ankles examined, the synovial folds were found to extend a mean of 20.05 mm (SD, 7.01 mm) from the DTFJ line into the recess where they were loosely attached to the fibular wall. In the remaining ankles, the synovial fold was limited to the DTFJ line leaving the recess devoid of a synovial fold. Intra-observer and inter-observer reliability of measurements was good to excellent (intra-class correlation coefficient, 0.61-0.99). An understanding of the morphology of the DTFJ synovial fold might help to explain ongoing ankle pain after injury, and why arthroscopic removal of the tissue might be therapeutic.

The retinacula of Weitbrecht in the adult hip.

PURPOSE: The aim of the study was to describe the retinacula of Weitbrecht in the adult hip. MATERIALS AND METHODS: Specimens were obtained from 30 adult hips, average age was 77 years (age range 43-91 years), 8 specimens were fixed by formalin solution and 22 were not fixed. RESULTS: Anterior retinaculum was found in 40% of examined specimens. The anterior retinaculum was in 83% of cases formed by a flat plate and in 17% by two to three parallel bands. Medial retinaculum was present constantly, extending from the attachment of the articular capsule at the base of the lesser trochanter towards the fovea capitis femoris as far as the edge of the articular cartilage. Typically, the retinaculum had the form of an inverted "T". Of the three retinacula, the medial one was the strongest. Lateral retinaculum was also present constantly. In 89% of cases, it had the form of a quadrilateral plate adjacent to the upper surface of the femoral neck. This plate arises from the insertion of the articular capsule on the upper part of the femoral neck at the base of the greater trochanter close to the trochanteric fossa. The plate extended along the upper edge of the femoral neck as far as the edge of the articular cartilage. Microscopic examination revealed fine blood vessels running through the retinacula. CONCLUSION: Lateral retinaculum and medial retinaculum are constant synovial plicae in terms of both occurrence and localization. Nutritive arteries run through both the plicae to supply the femoral head.

Morphometry of the synovial folds of the lateral atlanto-axial joints: the anatomical basis for understanding their potential role in neck pain.

PURPOSE: Intra-articular synovial folds of the cervical spine are considered to be a potential source of neck pain and disability. The purpose of the present study was to devise and validate a method to determine the normal morphometry of the synovial folds as a basis for understanding their functional and clinical significance. METHODS: Nine cadaver cervical spines were sectioned in the sagittal plane. The presence of the synovial folds at the lateral atlanto-axial joints was determined and their morphology described. Depth of projection, cross-sectional area and volume of the ventral and dorsal synovial folds of the right and left lateral atlanto-axial joints were measured from sagittal sections and compared. The relationship between synovial fold dimensions and subject age and cartilage degeneration were determined. Repeat measurements were made for the calculation of method reliability, and the water displacement method was used to determine method validity. RESULTS: There was a trend for ventral synovial folds to be larger than dorsal synovial folds. There was no correlation between synovial fold dimensions and age and extent of cartilage degeneration. Measurement reliability ranged from intraclass correlation coefficient 0.95-1.00 (intra-observer), 0.95-1.00 (test-retest) and 0.61-1.00 (inter-observer). Limits of agreement for the sectional and water displacement methods for the measurement of synovial fold volume were -1.04 ± 3.35 mm(3). CONCLUSIONS: A reliable method for quantifying synovial fold dimensions was devised. The results of this study provide a basis for the determination and diagnosis of pathologies affecting the synovial folds.

Optimization of a double inversion recovery sequence for noninvasive synovium imaging of joint effusion in the knee.

PURPOSE: We wanted to optimize a double inversion recovery (DIR) sequence to image joint effusion regions of the knee, especially intracapsular or intrasynovial imaging in the suprapatellar bursa and patellofemoral joint space. METHODS: Computer simulations were performed to determine the optimum inversion times (TI) for suppressing both fat and water signals, and a DIR sequence was optimized based on the simulations for distinguishing synovitis from fluid. In vivo studies were also performed on individuals who showed joint effusion on routine knee MR images to demonstrate the feasibility of using the DIR sequence with a 3T whole-body MR scanner. To compare intracapsular or intrasynovial signals on the DIR images, intermediate density-weighted images and/or post-enhanced T1-weighted images were acquired. RESULTS: The timings to enhance the synovial contrast from the fluid components were TI1 = 2830 ms and TI2 = 254 ms for suppressing the water and fat signals, respectively. Improved contrast for the intrasynovial area in the knees was observed with the DIR turbo spin-echo pulse sequence compared to the intermediate density-weighted sequence. CONCLUSIONS: Imaging contrast obtained noninvasively with the DIR sequence was similar to that of the post-enhanced T1-weighted sequence. The DIR sequence may be useful for delineating synovium without using contrast materials.

Synovial fibroblasts self-direct multicellular lining architecture and synthetic function in three-dimensional organ culture.

OBJECTIVE: To define the intrinsic capacity of fibroblast-like synoviocytes (FLS) to establish a 3-dimensional (3-D) complex synovial lining architecture characterized by the multicellular organization of the compacted synovial lining and the elaboration of synovial fluid constituents. METHODS: FLS were cultured in spherical extracellular matrix (ECM) micromasses for 3 weeks. The FLS micromass architecture was assessed histologically and compared with that of dermal fibroblast controls. Lubricin synthesis was measured via immunodetection. Basement membrane matrix and reticular fiber stains were performed to examine ECM organization. Primary human and mouse monocytes were prepared and cocultured with FLS in micromass to investigate cocompaction in the lining architecture. Cytokine stimuli were applied to determine the capacity for inflammatory architecture rearrangement. RESULTS: FLS, but not dermal fibroblasts, spontaneously formed a compacted lining architecture over 3 weeks in the 3-D ECM micromass organ cultures. These lining cells produced lubricin. FLS rearranged their surrounding ECM into a complex architecture resembling the synovial lining and supported the survival and cocompaction of monocyte/macrophages in the neo-lining structure. Furthermore, when stimulated by cytokines, FLS lining structures displayed features of the hyperplastic rheumatoid arthritis synovial lining. CONCLUSION: This 3-D micromass organ culture method demonstrates that many of the phenotypic characteristics of the normal and the hyperplastic synovial lining in vivo are intrinsic functions of FLS. Moreover, FLS promote survival and cocompaction of primary monocytes in a manner remarkably similar to that of synovial lining macrophages. These findings provide new insight into inherent functions of the FLS lineage and establish a powerful in vitro method for further investigation of this lineage.

MR findings of synovial disease in children and young adults: Part 1.

Synovial diseases in children can be classified into normal structures as potential sources of pathology (synovial folds: plicae, infrapatellar fat pad clefts); noninfectious synovial proliferation (juvenile idiopathic arthritis, hemophilic arthropathy, lipoma arborescens, synovial osteochondromatosis, pigmented villonodular synovitis, reactive synovitis), and infectious synovial proliferation, deposition disease, vascular malformations, malignancy (including metastasis) and intra-articular/periarticular cysts and cyst-like structures (ganglia). Familiarity with characteristic MR imaging findings of synovial diseases in children and young adults will enable a more confident diagnosis for earlier intervention and directed therapy. The first part of this paper will cover potential pathology of normal synovial structures as well as noninfectious synovial proliferation.

Magnetic resonance imaging of anatomical variations in the knee. Part 2: miscellaneous.

Magnetic resonance imaging is the modality of choice for investigation of internal derangement of the knee. The reporting radiologist must be familiar with both normal anatomy and anatomical variants within the knee, in order to avoid mis-diagnosis, over-investigation and unnecessary intervention. This article reviews the recognised anatomical variants of the non-ligamentous/musculotendinous structures of the knee, their anatomy, incidence and typical appearances on MRI.

Computational model of a synovial joint morphogenesis.

Joints enable the relative movement between the connected bones. The shape of the joint is important for the joint movements since they facilitate and smooth the relative displacement of the joint's parts. The process of how the joints obtain their final shape is yet not well understood. Former models have been developed in order to understand the joint morphogenesis leaning only on the mechanical environment; however, the obtained final anatomical shape does not match entirely with a realistic geometry. In this study, a computational model was developed with the aim of explaining how the morphogenesis of joints and shaping of ossification structures are achieved. For this model, both the mechanical and biochemical environments were considered. It was assumed that cartilage growth was controlled by cyclic hydrostatic stress and inhibited by octahedral shear stress. In addition, molecules such as PTHrP and Wnt promote chondrocyte proliferation and therefore cartilage growth. Moreover, the appearance of the primary and secondary ossification centers was also modeled, for which the osteogenic index and PTHrP-Ihh concentrations were taken into account. The obtained results from this model show a coherent final shape of an interphalangeal joint, which suggest that the mechanical and biochemical environments are crucial for the joint morphogenesis process.

MR imaging of synovial disorders of the knee.

Synovial membranes line the diarthrodial (movable) joints, bursae, and tendon sheaths of the body. The primary function of this specialized, vascular tissue is to serve as a filter system that lubricates and nourishes the articular structures as well as serving as a shock-absorber. The synovium is affected by a variety of disorders that can be localized to a specific articulation or can be systemic in nature. These include inflammatory, infectious, degenerative, traumatic, or neoplastic categories of disease. Further, MR imaging provides an excellent non-invasive tool for the evaluation of the synovium and synovial-based processes. This article will discuss technical considerations pertinent to the MR imaging evaluation of synovial processes in the knee; will review the synovial and bursal anatomy of the knee as well as the imaging characteristics of general synovial abnormalities and their diagnostic implications. In addition, it will review specific synovial processes and their characteristic MR imaging findings.