Joints

Question	Answer
What are the 3 main categories of joint?	1. Fibrous joint 2. Cartilaginous joint 3. Synovial joint
What is distinctive about fibrous joints and what is an example?	They are immobile, such as the skull sutures
What is distinctive about cartilaginous joints and what is an example?	They are slightly mobile, such as the intervertebral discs
What is distinctive about synovial joints and what is an example?	They are freely mobile, such as in limb joints
What are the 7 types of synovial joint?	1. Planar (sliding) 2. Hinge 3. Complex hinge 4. Ball and socket 5. Pivot 6. Saddle 7. Condyloid
Where would you find planar joints?	Intertarsal joints of the foot
Where would you find simple hinge joints? (2)	In the fingers, allowing digits to move up and down, or at the elbow
Where would you find ball and socket joints? (2)	At the shoulder and hip, allowing maximum movement but least stability
Where would you find pivot joints? (2)	1. Between the odontoid peg of the axis (CII) and atlas (CI) to allow rotation of the head 2. Between the radius and ulna to allow pronation/supination of the palms
Where would you find saddle joints?	At the carpo-metacarpal joint to allow movement of the thumb
Where would you find a complex hinge joint?	The knee, to allow both sliding and rotation
Where would you find a condyloid joint?	The joint between wrist and ulna, where the oval projection of wrist sits in an oval depression of the ulna
What are 5 ways to achieve joint stability?	1. Congruity (matching the shapes of the ends of bones to be joined) 2. Encasing the joint in a fibrous capsule which extends to form ligaments 3. Ligaments within the joint itself 4. Packing other materials around it (fat pads, menisci etc.) 5. Muscles around the joint to add stability and prevent dislocation (e.g. rotator cuff)
Describe the key features of a synovial joint (7)	1. The articular ends of each bone involved have a layer of avascular, articular cartilage 2. A synovial membrane surrounds the joint cavity, but does not line the articular cartilage 3. The joint cavity is filled with synovial fluid, which is constantly being replenished with the old fluid being removed into lymphatics 4. A fibrous capsule encases the entire joint 5. The synovium has vessels and lymphatics connected to it, supplying the membrane 6. Nociceptors are present in the ends of the bone, these are stimulated constantly in arthritis 7. Stretch receptors are present in the fibrous capsule which detect joint movement, limb positioning and proprioception
What are the 2 basic components of a proteoglycan?	1. glycosaminoglycan chains (GAGs) 2. Core protein
What is the most abundant proteoglycan in humans?	Aggrecan
What are the GAGs in aggrecan? (3)	1. Chondroitin sulfate 2. Keratan sulfate 3. Hyaluronan (hyaluronic acid)
What is the basic structure of aggrecan?	Chondroitin sulfate and keratan sulfate assemble around the central core protein, and hyaluronan binds them together
What is the function of the proteoglycans in cartilage?	Due to the highly negatively charged GAGs, water is drawn in to the cartilage and everything is bound by the collagen fibres, creating a fluid substance which can act as both a lubricant and a shock absorber
Describe the structure of the synovium (synovial membrane) (4)	1. Has very superficial capillaries with fenestrated membranes, allowing easy diffusion of water and other nutrients from the blood into the synovial fluid 2. There are Type A macrophages present, for immunological functions 3. There are Type B synoviocytes present, which are like fibroblasts in that they secrete. Synoviocytes secrete hyaluronan and lubricin 4. There is not a continuous barrier between the synovium and the joint cavity, allowing easy creation and drainage of synovial fluid
What are the main characteristics of synovial fluid? (3)	1. Similar electrolyte and protein content to other interstitial fluids 2. Contains hyaluronan to keep it viscous and help with lubrication 3. Contains lubricin to allow lubrication
How is synovial fluid dynamic?	The volume of fluid varies depending on movement. When in extension, the pressure in the joint is subatmospheric (negative), thus draws fluid in and causes synoviocytes to secrete more hyaluronan. Conversely, when in flexion, the pressure rises above atmospheric and thus fluid is pushed out and drains into lymphatics located in the subsynovium
What is usually the cause of acute monoarticular arthritis?	Trauma
What is usually the cause of acute polyarticular arthritis?	Infections
What can be the causes of chronic arthritis? (2)	1. Immune-mediated diseases (e.g. autoimmune) 2. Degenerative
What is the difference between rheumatoid arthritis (RA) and osteoarthritis (OA)?	RA is a systemic autoimmune inflammatory condition driven by cytokines (which can be measured in the blood), which causes the hypertrophy of the synovium (pannus) and synovitis. Osteoarthritis, however, is caused by metabolic changes in the joints, resulting in their narrowing and loss of cartilage, causing synovial inflammation. OA is usually more peripheral.
What is the cause of joint effusions in arthritis?	Inflammatory mediators that are involved in arthritis cause the endothelium of capillaries to become more permeable, vasodilation and increased capillary pressure, which results in more synovial fluid being formed and also the joint to feel hot (due to increased blood flow)
What are the 2 basic categories of arthritic conditions?	Inflammatory and non-inflammatory
What are 3 examples of inflammatory, poly symmetrical arthritic conditions?	1. RA 2. SLE 3. Psoriatic arthritis
Give 3 examples of oligo asymmetrical or mono arthritic conditions.	1. Reactive arthritis 2. Septic arthritis 3. Akylosing spondylitis
Why should you do tests such as blood cultures and joint aspirations before giving any treatment?	So that the measures are taken at baseline, eliminating any possibility that the results could be skewed by treatment.
What causes gout?	High uric acid levels causing crystals to be deposited into a joint, causing inflammation and extreme pain (usually only 1 joint)
What is the name given to a single deposition of urate in a joint?	Gouty tophi
If gout is left untreated, and thus the patients' serum urate levels are persistently high, what can be the result?	Chronic tophaceous gout
What is the treatment for acute gout? (2)	1. Anti-inflammatory treatment for the acute attack (NSAIDs, Steroids if necessary) 2. Drugs to reduce the serum uric acid level (Xanthine oxidase inhibitors, or drugs to increase urinary excretion of urate such as benzbromarone)
Why is it important to consider lifestyle changes when treating gout/chronic high levels of uric acid?	Chronic hyperuricaemia is associated with metabolic syndrome, which has a higher CV risk.
Why is it important to treat RA as early as possible?	To avoid irreversible deformity and disability
What is the treatment for RA? (3)	1. DMARDs such as methotrexate 2. Anti-inflammatory painkillers for acute flares (NSAIDs, steroids etc.) 3. Lifestyle changes

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	Created by Hannah Tribe about 10 years ago