Joints and Joint DiseaseHenry 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

BoneCartilageTendons Ligaments

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 CartilageSmooth 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 mesoderm

Form 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

Bursitis

Gout

Trauma

Reactive arthritis

BursitisWhat 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 movementsTraumaSystemic arthritis e.g. RA, gout

What is the treatment? Inject with steroid – in order to reduce the inflammation

Bursa

PrepatellarBursitis = Housemaids knee

InfrapatellarBursitis = Clergyman’s knee

SuprapatellarCommunicates with knee joint cavity

Patella tapMilk suprapatellar bursa inferiorly

then press patella posteriorly

OsteoarthritisWhat 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 cartilage2. Chondrocytes respond and proliferate3. Release of inflammatory mediators

(cytokines) and proteases4. 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 1st 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 joint3. 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