PATHOLOGY 8.2

• Osteo


  Bone
• Arthro


  Joint
• Itis


  Inflammation
• Osteoarthritis


  A condition characterized by a breakdown of synovial joint cartilage and, in time, underlying bone
• Articular cartilage


  The cartilage pad that covers the surface of a bone inside a joint cavity
• Subchondral bone


  Layer of bone just below the cartilage in a joint
• Chondrocytes


  A cartilage cell
• Matrix metalloproteinases 


  Enzymes which degrade extracellular matrix (i.e. collagen, laminin & fibronectin)
• Osteophytes


  A bony growth that develops on the edge of a bone
• Eburnation 


  Degenerative process of bone; friction in the joint causes reactive conversion to an ivory-like surface at the site of cartilage erosion
• Subchondral cyst


  Fluid-filled space inside a joint
• Autoimmune disease


  A disease in which the body’s immune system attacks healthy cells
• Pannus


  Growth of tissue in joints that can cause pain, swelling & damage to other tissues
• Extra-articular manifestations


  Conditions & symptoms which are not directly related to the musculoskeletal system
• Synovial tissue


  A layer of connective tissue that lines the cavities of joints
• Osteoarthritis Aetiology

  • Primary: no underlying cause
  • Secondary: underlying disease
• Osteoarthritis Pathogenesis

  • Changes to articular cartilage and subchondral bone
  • Chondrocytes shift from reparative to degenerative
• Mechanism for osteoarthritis

  Biomechanical or metabolic alterations induce an inflammatory response leading to the production of proinflammatory cytokines. Stimulation of chondrocytes by pro-inflammatory cytokines lead to the secretion of MMPs resulting in cartilage destruction. Subchondral bones rub together leading to pain, swelling and loss of motion
• Normal joint

  
• Osteoarthritic joint

  
• Clinical manifestations of osteoarthritis

  • Joint pain and joint stiffness
  • Becomes worse with overuse
• Heberden's nodes


  Bony enlargements on the distal interphalangeal joints (near the fingertips)
• Bouchard's nodes


  Bony growths on the proximal interphalangeal joints (middle of the fingers)
• To diagnose osteoarthritis, radiographic techniques are used to determine the presence of subchondral cysts, osteophytes, calcified cartilage and joint space narrowing
• Osteoarthritis management

  • NSAIDs
  • Intra-articular viscosupplementation
  • Glucosamine and chondroitin supplement
  • Intra-articular corticosteroids
  • Non-weight-bearing exercise
  • Weight loss
  • Joint replacement
• Rheumatoid arthritis


  An autoimmune disorder which targets and damages cells/tissues of the joint
• Rheumatoid arthritis pathogenesis

  Rheumatoid arthritis is a chronic autoimmune disease that begins with a T cell-mediated response in genetically predisposed individuals. This causes synovial inflammation and the formation of pannus, an inflamed tissue that erodes cartilage and bone. The pannus can eventually fuse the joint, making it unusable. Inflammatory mediators increase vascularity and cell division in the synovium, while RANKL production stimulates osteoclast activity, worsening bone loss.
• RA in synovial joint

  • Synovium: cells proliferate, pannus invades tissue
  • Synovial fluid: infiltration of inflammatory cells, angiogenesis
  • Cartilage: breakdown
  • Bone: Osteoclast activity, breakdown
• Both osteoarthritis and rheumatoid arthritis affect the synovial joint
• Pattern of involvement

  • Osteoarthritis: unilateral
  • Rheumatoid arthritis: bilateral
• Changes seen in osteoarthritic joint

  Loss of articular cartilage exposes the underlying bone, which then becomes the new joint surface. This exposure triggers osteoblast activity, leading to bone thickening and the formation of osteophytes. Communication between the joint cavity and underlying bone can force synovial fluid into the bone, forming bone cysts. This articular damage can subsequently lead to secondary inflammation.
• Changes seen in rheumatoid arthritic joint

  Severe inflammation with increased inflammatory cell infiltration into synovial tissue, synovial cell hyperplasia, angiogenesis with pannus invasion, and destruction of both cartilage and subchondral bone.
• Systemic symptoms of osteoarthritis and rheumatoid arthritis

  • Osteoarthritis: none
  • Rheumatoid arthritis: general unwell, tiredness, low grade fever
• Clinical presentation of osteoarthritis

  
  

  Patients generally present with deep aching pain in one or several joints (typically the hips, knees, or back), which is aggravated by use and relieved by rest. They usually experience stiffness after periods of immobility, which subsides with activity. The affected joint appears cool and hard on palpation, with a limited range of motion.
• Clinical presentation of rheumatoid arthritis

  Joints appear red, hot, and inflamed. Patients typically experience joint stiffness upon waking in the morning, which lasts for longer than an hour, as well as stiffness following prolonged periods of immobility.
• Pannus formation

  • Synovial cell hyperplasia and proliferation
  • Lots of inflammatory cells
  • Increased vascularity due to angiogenesis
  • Osteoclast activity in subchondral bone