Joints and Joint Disease Henry Delacave and Karina Bennett

Supporting Tissues Where is supporting tissue derived from? Embryonic mesoderm Supporting tissue is composed of cells (5%) and extracellular matrix (95%) What are the 4 types of supporting tissue? Why the variation? Due to amount of ground substance Vs. fibrous elements

Extracellular matrix (ECM) What is in the ECM? Ground substance Proteoglycan aggregates (GAGs around a protein core) Hyaluronic Acid Water Collagen (type 2 for cartilage)

Joint Structure Label the synovial joint…. Synovium (serous membrane) Synovial Fluid Lubricates joint Joint Capsule Hyaline Cartilage Smooth articular surface What is the role of the synovium? Sheet of fibrous connective tissue that secretes synovial fluid – lubricant and nutritional support for hyaline cartilage. Lines the capsule NOT the articular surfaces. This membrane also forms bursae and sheaths covering parts of tendons and ligaments

Cartilage What are the 3 types of cartilage? Hyaline, elastic and fibrocartilage Derived from mesodermForm chondroblasts Mitotic division forms clusters of chondroblasts These clusters synthesise the ECM ECM surrounds and segregates the chrondroblasts Chondroblasts mature into chondrocytes Peripheral chondroblasts persist in the perichondrium Describe the formation of cartilage? What is perichondrium? Surrounds the perimeter of the cartilage and contains capillaries provides nutrients. But not around fibrocartilage and articular surfaces. Articular surface relies on synovial fluid to get nutrients

Joint diseases Common joint diseases Osteoarthritis Rheumatoid arthritis BursitisGoutTrauma Reactive arthritis

Bursitis What are bursa? Fluid filled sac which provides friction free movement between bones and tendons around a joint. Some are isolated and some communicate freely. How does it present? Localised pain (acute inflammation) and tenderness on palpation. Think of the signs of acute inflammation: rubor, calor, tumor, dalor, & loss of function. Name some possible causes? Repetitive movements Trauma Systemic arthritis e.g. RA, gout What is the treatment? Inject with steroid – in order to reduce the inflammation

Bursa Prepatellar Bursitis = Housemaids knee Infrapatellar Bursitis = Clergyman’s knee Suprapatellar Communicates with knee joint cavity Patella tap Milk suprapatellar bursa inferiorly then press patella posteriorly

Osteoarthritis What are the risk factors for OA? >50 years, gender, white, obese/ anorexics, joint defects. What is the process of degeneration in OA? 1.Erosion of cartilage 2.Chondrocytes respond and proliferate 3.Release of inflammatory mediators (cytokines) and proteases 4.Proteases break down the cartilage, releasing proteoglycans. This induces an osmotic pressure which means water is absorbed. 5.Bone that touches becomes shiny and smooth - eburnation. 6.Development of osteophytes, joint mice and bone cysts 7.Hyperplasia of synovium - causing joint swellings.

Osteoarthritis What does the joint look like? Osteophytes Eburnation Joint mice Loss of articular hyaline cartilage Change in composition of cartilage – reduced proteoglycans Synovium hyperplasia Bone cysts Heberden’s nodes Bouchard’s nodes

Classic presentation of OA….. What are the symptoms/ signs… Aching, enlarged and hard joint Grinding (crepitations) Other joints affected through compensation Typically affecting: PIP, DIP and 1 st carpometacarpal joint and can be unilateral Normal bloods (unlike RA) No/little morning stiffness (unlike RA)

Gout What is the process by which gout occurs? 1.Hyperuricaemia 2.Urate crystals deposit in joint 3.Activates complement 4.Phagocytosis of gout crystals 5.Lysis of neutrophils 6.Release of lysosomal enzymes 7.Tissue injury and inflammation What is this? Tophi – deposit of monosodium urate crystals BEWARE!: Pseudogout (aka crystal arthritis)… Calcium pyrophosphate crystals depsosition. Risk factors: old age, hyperparathyoidism, haemochromatosis, hypophosphataemia.

Questions What would you see on an OA x-ray? Joint space narrowed Osteophytes (bone spurs) Cyst spaces DO NOT SEE THE MICE! How does the articular surface get nutrients? It does not have a perichondrium and therefore no vascular (capillary) supply. It relies on synovial fluid to get nutrients. What are the three components of chronic inflammation? Ongoing inflammation Ongoing tissue destruction Ongoing tissue repair