Synovial joint

[ Synovial fluid, also called synovia, Structure [ ] The inner membrane of synovial joints is called the weeping lubrication). The functions of the synovial fluid include: • reduction of friction — synovial fluid lubricates the articulating joints [ pageneeded] • shock absorption — as a [ dubious – • nutrient and waste transportation — the fluid supplies oxygen and nutrients and removes carbon dioxide and metabolic wastes from the • molecular sieving - pressure within the joint forces Composition [ ] Synovial tissue is sterile (meaning microorganisms are not typically found there [ unreliable medical source?] Hyaluronan is synthesized by the synovial membrane and secreted into the joint cavity to increase the viscosity and elasticity of articular cartilages and to lubricate the surfaces between [ unreliable medical source?] Synovial fluid contains It also contains Clinical significance [ ] Collection [ ] Synovial fluid may be collected by syringe in a procedure termed Classification [ ] Synovial fluid may be classified into normal, noninflammatory, inflammatory, septic, and hemorrhagic: Classification of synovial fluid in an adult Normal Non-inflammatory Inflammatory Septic Bleeding Volume (ml) 3.5 >3.5 >3.5 >3.5 High High Low Mixed Low Clarity Clear Clear Cloudy Opaque Mixed Color Colorless/straw Straw/yellow Yellow Mixed Red 3 50,000 Similar to blood level 70 Similar to blood level None None None + (S aureus & Streptococcus) - (Neisseria gonorrhoeae) None Glucose (mg/dl)...

Joints are the areas where two or more bones meet. Most joints are mobile, allowing the bones to move. Joints consist of the following: • Cartilage. A type of tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint. • Synovial membrane. A tissue called the synovial membrane lines the joint and seals it into a joint capsule. The synovial membrane secretes a clear, sticky fluid (synovial fluid) around the joint to lubricate it. • Ligaments. Strong ligaments (tough, elastic bands of connective tissue) surround the joint to give support and limit the joint's movement. Ligaments connect bones together. • Tendons. Tendons (another type of tough connective tissue) on each side of a joint attach to muscles that control movement of the joint. Tendons connect muscles to bones. • Bursas. Fluid-filled sacs, called bursas, between bones, ligaments, or other nearby structures. They help cushion the friction in a joint. • Synovial fluid. A clear, sticky fluid secreted by the synovial membrane. • Femur. This is the thighbone. • Tibia. This is the shin bone. • Patella. This is the kneecap. • Meniscus. This is a curved part of cartilage in the knees and other joints. What are the different types of joints? There are many types of joints, including joints that don’t move in adults, such as the suture joints in the skull. Joints that don’t move are called fixed. Other joints may move a little, such as the vertebrae. Examples of mobil...

• The fluid's physical qualities (color, thickness, viscosity), which can reveal inflammation • Its chemical makeup, to look for changes that may be related to a disease process • Microscopic contents that are undesirable, such as crystals (which indicate gout) and bacteria (which indicate infection) • Arthritis Foundation. • Zhang SL, Liu HQ, Xu XZ, Zhi J, Geng JJ, Chen J. Mol Med Rep. 2013;7(1):183-186. doi:10.3892/mmr.2012.1168 • Castrogiovanni P, Trovato FM, Loreto C, et al. Int J Mol Sci. 2016;17(12):2042. doi:10.3390/ijms17122042 • Tamer TM. Interdiscip Toxicol. 2013;6(3):111-125. doi:10.2478/intox-2013-0019 • Belk JW, Kraeutler MJ, Houck DA, et al. Am J Sports Med. 2021;49(1):249-260. doi:10.1177/0363546520909397 Additional Reading

• 01/04/2019 The synovial membrane (sometimes referred to as the synovium) is the inner lining of the joint. This inner lining secretes synovial fluid to cushion the joints during movement. Synovium serves an important function in the joint capsules in the knee, ankle, wrist, elbow, hand, foot, and shoulder. But the synovium can become inflamed, causing a condition known as synovitis. Synovitis can lead to various problems from tenderness to hypertrophy. Often the result of repeated joint bleeds, synovitis can worsen over time if not addressed appropriately, leading to even more bleeding into the joint. Synovitis Symptoms Signs and symptoms of synovitis depend on what area of the body is affected. Typically, most people with synovitis will experience these symptoms: • Joint pain that ranges from mild to severe • Swelling • Difficulty moving the affected area • Thickening of the tissue • Increased blood flow to the affected area • Increased fluid production Synovitis Causes Many things can cause synovitis. Sometimes, synovitis is caused by structural damage in the affected area. This can include things like articular cartilage damage, a labrum tear, or a tear in the ligamentum teres. Other times, synovitis can be caused by diseases that affect the synovium. Rheumatologic diseases in particular such as Synovitis vs Arthritis: Is Synovitis the Same as Arthritis? Yes and no. While synovitis and arthritis both have to do with joint inflammation, they have their differences. Syn...

• 1 Anatomical Structure • 1.1 Articulating Surfaces • 1.2 Joint Capsule • 1.3 Ligaments • 1.4 Bursae • 2 Movements • 3 Mobility and Stability • 4 Blood Supply • 5 Innervation • 6 Clinical Relevance: Common Injuries • 6.1 Dislocation of the Shoulder Joint • 6.2 Rotator Cuff Tendonitis The shoulder joint (glenohumeral joint) is an articulation between the It is a ball and socket-type synovial joint, and one of the most mobile joints in the human body. In this article, we shall look at the anatomy of the shoulder joint – its structure, blood supply, and clinical correlations. Anatomical Structure Articulating Surfaces The shoulder joint is formed by an articulation between the head of the humerus and the glenoid cavity (or fossa) of the scapula. This gives rise to the alternate name for the shoulder joint – the glenohumeral joint. Like most synovial joints, the articulating surfaces are covered with hyaline cartilage. The head of the humerus is much larger than the glenoid fossa, giving the joint a wide range of movement at the cost of instability. To reduce the disproportion in surfaces, the glenoid fossa is deepened by a fibrocartilage rim – called the glenoid labrum. By Fig 1 – The articulating surfaces of the shoulder joint. Joint Capsule The joint capsule is a fibrous sheath which encloses the structures of the joint. It extends from the anatomical neck of the humerus to the border or ‘rim’ of the glenoid fossa. The joint capsule is lax – permitting greater mobility (pa...

• 1 Key Structures of a Synovial Joint • 1.1 Articular Capsule • 1.2 Articular Cartilage • 1.3 Synovial Fluid • 2 Accessory Structures of a Synovial Joint • 2.1 Accessory Ligaments • 2.2 Bursae • 3 Innervation • 4 Vasculature • 5 Clinical Relevance: Osteoarthritis A synovial joint is characterised by the presence of a fluid-filled joint cavity contained within a fibrous capsule. It is the most common type of joint found in the human body, and contains several structures which are not seen in fibrous or cartilaginous joints. In this article we shall look at the anatomy of a synovial joint – the joint capsule, neurovascular structures and clinical correlations. Key Structures of a Synovial Joint The three main features of a synovial joint are: (i) articular capsule, (ii) articular cartilage, (iii) synovial fluid. Articular Capsule The articular capsule surrounds the joint and is continuous with the periosteum of articulating bones. It consists of two layers: • Fibrous layer (outer) – consists of white fibrous tissue, known the capsular ligament. It holds together the articulating bones and supports the underlying synovium. • Synovial layer (inner) – a highly vascularised layer of serous connective tissue. It absorbs and secretes synovial fluid, and is responsible for the mediation of nutrient exchange between blood and joint. Also known as the synovium. Adapted from work by OpenStax College [CC BY 3.0], via Wikimedia Commons Fig 1 – The basic structures of a synovial joint. ...

• Synarthroses: These are fixed, immovable joints formed by the connection of two or more bones. • Amphiarthroses: These are slightly movable joints that allow for a very small degree of movement, also known as cartilaginous joints. The bones that form the joints are separated by a fibrocartilage disc. • Diarthroses: These are the most common freely moving joints that allow movement in multiple directions, also called synovial joints. The bones that form the joints are lined with articular cartilage and enclosed in a joint capsule filled with • The knee joint that allows the knee to bend and extend • The elbow joint that allows the elbow to bend and extend • The finger and toe joints that allow the fingers and toes to bend and extend • The talocrural joint of the ankle that allows the ankle to move up (dorsiflexion) and down (plantarflexion) Function Hinge joints allow for movement of the limbs, fingers, and toes to extend away and bend in toward the body. Movement of the hinge joints of the knees, shoulders, ankles, fingers, and toes are essential for all daily functions, from activities of daily living like bathing, getting dressed, and eating, to everyday movements like walking and standing up and sitting down. Other conditions that affect hinge joints include injuries to the cartilage within the joints or ligaments that stabilize the outside of the joints. Ligament sprains or tears can result from jamming the fingers or toes, rolling the ankles, and twisting injuries o...