Chapter 26: Joints Flashcards
What are the 3 major components of hyaline cartilage?
70% H2O + 10% type II collagen + 8% proteoglycans
Which joints are most commonly affected in osteoarthritis in men vs. women?
- Men = hips
- Women = hands and knees
What are the 3 phases of changes to chondrocytes seen with the pathogenesis of osteoarthritis?
- Chondrocyte injury, related to genetic and enviornmental factors
- Early OA: proliferation for remodeling of cartilaginous matrix and secondary inflammatory changes
- Late OA: repetitive injury and chronic inflammation lead to chondrocyte drop out, marked cartilage loss, and extensive subchondral bone changes
Which cytokines and diffusable factors have been implicated in the pathogenesis in osteoarthritis?
- TGF-β –> which induces MMP’s
- TNF
- Prostaglandins
- Nitric oxide
What are 3 characteristic morphological findings of osteoarthritis?
- Hunks of dead cartilage sloughed into the joint –> ‘joint mice’
- Subchondrondal bone exposed and rubbed smooth = eburnation
- Microfractures and cysts develop
- Mushroom-shaped osteophytes (bony outgrowths)
Deep, achy pain that worsens with use, morning stiffness, crepitus, and limitation of ROM is characteristic of what?
Osteoarthritis
What are the prominent osteophytes which may form at the PIP and DIP joints of pt with osteoarthritis called?
- PIP = Bouchard’s nodes
- DIP = Heberden node
Which joint disease may progress to deformity with time and which may progress to fusion?
- OA may progress to joint deformity, not fusion
- RA progresses to fusion
OA is a disease of what vs. RA?
- OA = disease of cartilage
- RA = disease of synovium
Which inflammatory cells may initiate the autoimmune response in RA and how?
CD4+ T helper cell by reacting with an arthritogenic agent, perhaps microbial or a self-antigen
What are the most important cytokines isolated from the inflammed joint in person with RA; what is their role in the disease?
- IFN-γ from TH1 cells activate macrophages and resident synovial cells
- IL-17 from TH17 cells recruit neutrophils and monocytes
- TNF and IL-1 from macrophages stimulate resident synovial cells to secrete proteases that destro__y hyaline cartilage
- RANKL on activated T cells stimulate bone resportion
Which cytokine has been most firmly implicated in the pathogenesis of RA?
TNF
Many of the autoantibodies produced in the lymphoid organs and in the synovium of pt with RA are specific for what?
Citrullinated peptides (CCPs)
What are 2 genetic factors associated with RA?
HLA-DRB1 alleles & PTPN22 gene
What are 5 characteristic histologic features of RA?
- Synovial cell hyperplasia and proliferation
- Dense inflammatory infiltrates of CD4+ cells, B cells, plasma cells, dendritic cells, and macrophages
- ↑ vascularity due to angiogenesis
- Fibrinopurulent exudate on synovial and joint surfaces
- Osteoclastic activity in underlying bone –> periarticular erosions ad subchondral cysts
Which characteristic mass of edematous synovium, inflammatory cells, granulation tissue, and fibroblasts growing over articular cartilage is seen in joints affected by RA?
Pannus
With time in RA, the pannus bridges apposing bones to form what?
Fibrous ankylosis, which eventually ossifies and results in fusion of the bones, called bony ankylosis
Which skin lesions are commonly seen in RA, what is their morphology?
- Rheumatoid nodules: firm, non-tender, and round arising in subcutaneous tissue
- Resemble necrotizing granulomas w/ central zone of fibrinoid necrosis + prominent rim of macrophages, lymphocytes and plasma cells.
Where are rheumatoid nodules most commonly seen?
Extensor surfaces at pressure points
How may the blood vessels of patient with RA be affected and which vessels specifically?
- Risk of acute necrotizing vasculitis of small and large arteries
- May involve the pleura, pericardium or lung evolving into chronic fibrosing process
- Obliterating endarteritis —> peripheral neuropathy, ulcers, and gangrene may occur
Inflammation in the tendons, ligaments, and occassionally adjacent skeletal muscle accompanying RA produces what characteristic findings in the hands?
- Radial deviation of the wRrist
- UlNar deviation of the fiNgers
- Boutonniere: deformity of finger –> hyperextension of DIP w/ flexion of PIP
- Swan-neck: hyperextension of PIP, flexion of DIP
What are the radiographic hallmarks of RA?
Joint effusions and juxta-articular osteopenia w/ erosions and narrowing of the joint space + loss of articular cartilage
Diagnosis of RA, especially with presence of multisystem involvement, is supported by what 3 findings?
- Characteristic radiohgraphic findings
- Sterile, turbid synovial fluid w/ ↓ viscosity, poor mucin clot formation, and inclusion-bearing neutrophils
- Combo of rheumatoid factor and anti-CCP antibody
How do the joints being affected differ between OA and RA?
- OA: usually large, weight bearing joints
- RA: symmetrical pattern w/ small joints affected first
How does activity affect the pain in OA vs. RA?
- OA = worse with activity
- RA = improves with activty, worse with rest
What may develop in the knee as increased intra-articular pressure causes herniation of synovium in some pt’s with RA?
Baker cyst of the posterior knee