ArthritisSynovial Fluid: The clear, viscous fluid secreted by the SYNOVIAL MEMBRANE. It contains mucin, albumin, fat, and mineral salts and serves to lubricate joints.Arthritis, Rheumatoid: A chronic systemic disease, primarily of the joints, marked by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Etiology is unknown, but autoimmune mechanisms have been implicated.Synovial Membrane: The inner membrane of a joint capsule surrounding a freely movable joint. It is loosely attached to the external fibrous capsule and secretes SYNOVIAL FLUID.Chronic Disease: Diseases which have one or more of the following characteristics: they are permanent, leave residual disability, are caused by nonreversible pathological alteration, require special training of the patient for rehabilitation, or may be expected to require a long period of supervision, observation, or care. (Dictionary of Health Services Management, 2d ed)Arthritis, Experimental: ARTHRITIS that is induced in experimental animals. Immunological methods and infectious agents can be used to develop experimental arthritis models. These methods include injections of stimulators of the immune response, such as an adjuvant (ADJUVANTS, IMMUNOLOGIC) or COLLAGEN.Arthritis, Psoriatic: A type of inflammatory arthritis associated with PSORIASIS, often involving the axial joints and the peripheral terminal interphalangeal joints. It is characterized by the presence of HLA-B27-associated SPONDYLARTHROPATHY, and the absence of rheumatoid factor.Arthritis, Infectious: Arthritis caused by BACTERIA; RICKETTSIA; MYCOPLASMA; VIRUSES; FUNGI; or PARASITES.Joints: Also known as articulations, these are points of connection between the ends of certain separate bones, or where the borders of other bones are juxtaposed.Arthritis, Juvenile: Arthritis of children, with onset before 16 years of age. The terms juvenile rheumatoid arthritis (JRA) and juvenile idiopathic arthritis (JIA) refer to classification systems for chronic arthritis in children. Only one subtype of juvenile arthritis (polyarticular-onset, rheumatoid factor-positive) clinically resembles adult rheumatoid arthritis and is considered its childhood equivalent.Synovitis: Inflammation of a synovial membrane. It is usually painful, particularly on motion, and is characterized by a fluctuating swelling due to effusion within a synovial sac. (Dorland, 27th ed)Arthritis, Reactive: An aseptic, inflammatory arthritis developing secondary to a primary extra-articular infection, most typically of the GASTROINTESTINAL TRACT or UROGENITAL SYSTEM. The initiating trigger pathogens are usually SHIGELLA; SALMONELLA; YERSINIA; CAMPYLOBACTER; or CHLAMYDIA TRACHOMATIS. Reactive arthritis is strongly associated with HLA-B27 ANTIGEN.Osteoarthritis: A progressive, degenerative joint disease, the most common form of arthritis, especially in older persons. The disease is thought to result not from the aging process but from biochemical changes and biomechanical stresses affecting articular cartilage. In the foreign literature it is often called osteoarthrosis deformans.Spondylitis, Ankylosing: A chronic inflammatory condition affecting the axial joints, such as the SACROILIAC JOINT and other intervertebral or costovertebral joints. It occurs predominantly in young males and is characterized by pain and stiffness of joints (ANKYLOSIS) with inflammation at tendon insertions.Spondylarthropathies: Heterogeneous group of arthritic diseases sharing clinical and radiologic features. They are associated with the HLA-B27 ANTIGEN and some with a triggering infection. Most involve the axial joints in the SPINE, particularly the SACROILIAC JOINT, but can also involve asymmetric peripheral joints. Subsets include ANKYLOSING SPONDYLITIS; REACTIVE ARTHRITIS; PSORIATIC ARTHRITIS; and others.Mice, Inbred DBATenosynovitis: Inflammation of the synovial lining of a tendon sheath. Causes include trauma, tendon stress, bacterial disease (gonorrhea, tuberculosis), rheumatic disease, and gout. Common sites are the hand, wrist, shoulder capsule, hip capsule, hamstring muscles, and Achilles tendon. The tendon sheaths become inflamed and painful, and accumulate fluid. Joint mobility is usually reduced.Collagen Type II: A fibrillar collagen found predominantly in CARTILAGE and vitreous humor. It consists of three identical alpha1(II) chains.Rheumatoid Factor: Antibodies found in adult RHEUMATOID ARTHRITIS patients that are directed against GAMMA-CHAIN IMMUNOGLOBULINS.Injections, Intra-Articular: Methods of delivering drugs into a joint space.Antirheumatic Agents: Drugs that are used to treat RHEUMATOID ARTHRITIS.Arthritis, Gouty: Arthritis, especially of the great toe, as a result of gout. Acute gouty arthritis often is precipitated by trauma, infection, surgery, etc. The initial attacks are usually monoarticular but later attacks are often polyarticular.Gout: Hereditary metabolic disorder characterized by recurrent acute arthritis, hyperuricemia and deposition of sodium urate in and around the joints, sometimes with formation of uric acid calculi.Tumor Necrosis Factor-alpha: Serum glycoprotein produced by activated MACROPHAGES and other mammalian MONONUCLEAR LEUKOCYTES. It has necrotizing activity against tumor cell lines and increases ability to reject tumor transplants. Also known as TNF-alpha, it is only 30% homologous to TNF-beta (LYMPHOTOXIN), but they share TNF RECEPTORS.Osteoclasts: A large multinuclear cell associated with the BONE RESORPTION. An odontoclast, also called cementoclast, is cytomorphologically the same as an osteoclast and is involved in CEMENTUM resorption.Inflammation: A pathological process characterized by injury or destruction of tissues caused by a variety of cytologic and chemical reactions. It is usually manifested by typical signs of pain, heat, redness, swelling, and loss of function.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Glucose-6-Phosphate Isomerase: An aldose-ketose isomerase that catalyzes the reversible interconversion of glucose 6-phosphate and fructose 6-phosphate. In prokaryotic and eukaryotic organisms it plays an essential role in glycolytic and gluconeogenic pathways. In mammalian systems the enzyme is found in the cytoplasm and as a secreted protein. This secreted form of glucose-6-phosphate isomerase has been referred to as autocrine motility factor or neuroleukin, and acts as a cytokine which binds to the AUTOCRINE MOTILITY FACTOR RECEPTOR. Deficiency of the enzyme in humans is an autosomal recessive trait, which results in CONGENITAL NONSPHEROCYTIC HEMOLYTIC ANEMIA.Knee Joint: A synovial hinge connection formed between the bones of the FEMUR; TIBIA; and PATELLA.Cartilage, Articular: A protective layer of firm, flexible cartilage over the articulating ends of bones. It provides a smooth surface for joint movement, protecting the ends of long bones from wear at points of contact.Finger Joint: The articulation between the head of one phalanx and the base of the one distal to it, in each finger.Autoantibodies: Antibodies that react with self-antigens (AUTOANTIGENS) of the organism that produced them.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Metacarpophalangeal Joint: The articulation between a metacarpal bone and a phalanx.Foot Joints: The articulations extending from the ANKLE distally to the TOES. These include the ANKLE JOINT; TARSAL JOINTS; METATARSOPHALANGEAL JOINT; and TOE JOINT.Rats, Inbred LewRheumatic Diseases: Disorders of connective tissue, especially the joints and related structures, characterized by inflammation, degeneration, or metabolic derangement.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Mice, Inbred C57BLMice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Rheumatology: A subspecialty of internal medicine concerned with the study of inflammatory or degenerative processes and metabolic derangement of connective tissue structures which pertain to a variety of musculoskeletal disorders, such as arthritis.Interleukin-1beta: An interleukin-1 subtype that is synthesized as an inactive membrane-bound pro-protein. Proteolytic processing of the precursor form by CASPASE 1 results in release of the active form of interleukin-1beta from the membrane.Spondylarthritis: Inflammation of the joints of the SPINE, the intervertebral articulations.Methotrexate: An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.RANK Ligand: A transmembrane protein belonging to the tumor necrosis factor superfamily that specifically binds RECEPTOR ACTIVATOR OF NUCLEAR FACTOR-KAPPA B and OSTEOPROTEGERIN. It plays an important role in regulating OSTEOCLAST differentiation and activation.Wrist Joint: The joint that is formed by the distal end of the RADIUS, the articular disc of the distal radioulnar joint, and the proximal row of CARPAL BONES; (SCAPHOID BONE; LUNATE BONE; triquetral bone).Arthralgia: Pain in the joint.Bone Resorption: Bone loss due to osteoclastic activity.Gout Suppressants: Agents that increase uric acid excretion by the kidney (URICOSURIC AGENTS), decrease uric acid production (antihyperuricemics), or alleviate the pain and inflammation of acute attacks of gout.Cytokines: Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.Autoimmune Diseases: Disorders that are characterized by the production of antibodies that react with host tissues or immune effector cells that are autoreactive to endogenous peptides.Peptides, Cyclic: Peptides whose amino and carboxy ends are linked together with a peptide bond forming a circular chain. Some of them are ANTI-INFECTIVE AGENTS. Some of them are biosynthesized non-ribosomally (PEPTIDE BIOSYNTHESIS, NON-RIBOSOMAL).Edema: Abnormal fluid accumulation in TISSUES or body cavities. Most cases of edema are present under the SKIN in SUBCUTANEOUS TISSUE.Joint DiseasesHindlimb: Either of two extremities of four-footed non-primate land animals. It usually consists of a FEMUR; TIBIA; and FIBULA; tarsals; METATARSALS; and TOES. (From Storer et al., General Zoology, 6th ed, p73)HLA-B27 Antigen: A specific HLA-B surface antigen subtype. Members of this subtype contain alpha chains that are encoded by the HLA-B*27 allele family.Collagen: A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of SKIN; CONNECTIVE TISSUE; and the organic substance of bones (BONE AND BONES) and teeth (TOOTH).Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Receptor Activator of Nuclear Factor-kappa B: A tumor necrosis factor receptor family member that is specific for RANK LIGAND and plays a role in bone homeostasis by regulating osteoclastogenesis. It is also expressed on DENDRITIC CELLS where it plays a role in regulating dendritic cell survival. Signaling by the activated receptor occurs through its association with TNF RECEPTOR-ASSOCIATED FACTORS.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)Interleukin-17: A proinflammatory cytokine produced primarily by T-LYMPHOCYTES or their precursors. Several subtypes of interleukin-17 have been identified, each of which is a product of a unique gene.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Inflammation Mediators: The endogenous compounds that mediate inflammation (AUTACOIDS) and related exogenous compounds including the synthetic prostaglandins (PROSTAGLANDINS, SYNTHETIC).Interleukin-1: A soluble factor produced by MONOCYTES; MACROPHAGES, and other cells which activates T-lymphocytes and potentiates their response to mitogens or antigens. Interleukin-1 is a general term refers to either of the two distinct proteins, INTERLEUKIN-1ALPHA and INTERLEUKIN-1BETA. The biological effects of IL-1 include the ability to replace macrophage requirements for T-cell activation.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Psoriasis: A common genetically determined, chronic, inflammatory skin disease characterized by rounded erythematous, dry, scaling patches. The lesions have a predilection for nails, scalp, genitalia, extensor surfaces, and the lumbosacral region. Accelerated epidermopoiesis is considered to be the fundamental pathologic feature in psoriasis.T-Lymphocytes: Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Health Fairs: Community health education events focused on prevention of disease and promotion of health through audiovisual exhibits.Freund's Adjuvant: An antigen solution emulsified in mineral oil. The complete form is made up of killed, dried mycobacteria, usually M. tuberculosis, suspended in the oil phase. It is effective in stimulating cell-mediated immunity (IMMUNITY, CELLULAR) and potentiates the production of certain IMMUNOGLOBULINS in some animals. The incomplete form does not contain mycobacteria.Mice, Inbred NOD: A strain of non-obese diabetic mice developed in Japan that has been widely studied as a model for T-cell-dependent autoimmune insulin-dependent diabetes mellitus in which insulitis is a major histopathologic feature, and in which genetic susceptibility is strongly MHC-linked.Cartilage: A non-vascular form of connective tissue composed of CHONDROCYTES embedded in a matrix that includes CHONDROITIN SULFATE and various types of FIBRILLAR COLLAGEN. There are three major types: HYALINE CARTILAGE; FIBROCARTILAGE; and ELASTIC CARTILAGE.Interleukin 1 Receptor Antagonist Protein: A ligand that binds to but fails to activate the INTERLEUKIN 1 RECEPTOR. It plays an inhibitory role in the regulation of INFLAMMATION and FEVER. Several isoforms of the protein exist due to multiple ALTERNATIVE SPLICING of its mRNA.Interleukin-6: A cytokine that stimulates the growth and differentiation of B-LYMPHOCYTES and is also a growth factor for HYBRIDOMAS and plasmacytomas. It is produced by many different cells including T-LYMPHOCYTES; MONOCYTES; and FIBROBLASTS.HLA-DR Antigens: A subclass of HLA-D antigens that consist of alpha and beta chains. The inheritance of HLA-DR antigens differs from that of the HLA-DQ ANTIGENS and HLA-DP ANTIGENS.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Early Diagnosis: Methods to determine in patients the nature of a disease or disorder at its early stage of progression. Generally, early diagnosis improves PROGNOSIS and TREATMENT OUTCOME.Anti-Inflammatory Agents: Substances that reduce or suppress INFLAMMATION.Autoimmunity: Process whereby the immune system reacts against the body's own tissues. Autoimmunity may produce or be caused by AUTOIMMUNE DISEASES.Statistics, Nonparametric: A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1284; Corsini, Concise Encyclopedia of Psychology, 1987, p764-5)Biological Markers: Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.Receptors, Tumor Necrosis Factor: Cell surface receptors that bind TUMOR NECROSIS FACTORS and trigger changes which influence the behavior of cells.