Overview of Arthridities: Patterns, Synovial Fluid Analysis, and Septic Arthritis Flashcards
What is meant by mono vs oligo vs polyarthritis?
Mono - one joint
Oligo - 2-4 joints
Poly - 5+ joints
What type of arthritis are septic arthritis, gout, pseudogout, and reactive arthritis typically?
Typically they are classed as acute, inflammatory monoarthritis
What is meant by the intima and subintima of the synovium? What does this membrane lack versus other tissue types?
Intima - specialized macrophages and fibroblasts which line the synovium. The intimal fibroblasts secrete the hyaluronic acid.
Subintima - blood and lymphatics in a collagenous extracelllular matrix
Lacks a basement membrane -> keeps the chemical environment of the joint relatively homogenous with the surrounding tissues
How will the color of the synovial fluid appear in hemarthroses vs inflammatory arthropathies vs septic arthritis?
Hemarthroses - red or orange
Inflammatory arthropathies - cream or white
Septic arthritis - purulent and often discolored by bacterial chromogens
What is the normal nucleated cell count in synovial fluid and what is the minimum threshold for inflammatory joint disease? What conditions can cause extremely elevated counts?
Normal: <200 cells/uL
Inflammatory: >2,000 cells / uL
Extremely inflammatory: >50,000 cells /uL 4 conditions: 1. Acute rheumatoid flares 2. Septic arthritis 3. Acute crystal arthritis 4. Reactive arthritis
These are mostly PMNs
What cell types are present in non-inflammatory arthropathies? What color is this fluid? Give an example condition.
This is the 200-2000 cell range. Typically they are lymphocytes, macrophages, and synoviocytes (fibroblast-like cells)
Fluid is clear and yellow, as in osteoarthritis
How does the viscosity of the synovial fluid change with inflammation?
It decreases markedly. Think about inflammation causing massive edema, which makes the synovial fluid runny. Normal synovial fluid is clear, colorless, and very viscous.
What is the definition of septic arthritis and who is it most common in?
Infection of a joint space, most often caused by hematogenous spread of organisms from a distant infection site.
Most common in CHILDREN (2-5 years old), despite the fact that it is rarely caused by osteomyelitis.
What is the most common cause of septic arthritis overall and in young adults?
Overall - Staph aureus
Young adults - if sexually active, Neisseria gonorrhea
What accounts for the major of septic arthritis in prosthetic hips and knees? What other bacteria does first aid list as a prime cause of septic arthritis?
S. aureus and coagulase-negative staphylococcal species account for >50% of septic arthritis in these patients
Streptococcus species (i.e. Group A strept) are another major cause
What is a common cause of septic arthritis in neonates? Do viral infections ever cause septic arthritis?
Neonates - Group B streptococcus (agalactiae)
Viral - primary joint infections are rare, but immune-mediated arthritis accompanies many viral syndromes (i.e. Parvovirus B19, Rubella)
Why does bacteria spread so easily to the joints and why is septic arthritis so dangerous?
Because the synovial membrane lacks a basement membrane.
Bacterial products in the joint space induce TNFalpha and IL-1 production -> neutrophilic chemotaxis, release of elastases and protelytic enzymes.
Pressure rises in the joint space, compromising vascular supply, inducing necrosis of cartilage, and enzymatically destroying cartilage.
How many joints and what joints are typically involved in septic arthritis?
Usually one joint, and usually the knee
But in infants / young children, the hip is more commonly infected
What is gonococcal dermatitis-arthritis syndrome? Who is at greatest risk?
Triad of pustules, migratory polyarthritis, and tenosynovitis
Greatest risk are sexuually active women, especially those with terminal complement deficiencies (C5-C9)
How do you typically diagnose septic arthritis of the hip vs a typical knee arthritis?
Knee arthritis - typically swollen, red, and painful
Hip arthritis - more difficult to palpate because the joint is deep
-> limited range of motion and refusal to walk is highly suggestive of the diagnosis
Patient often has fever as well
What joints and tendon sheaths are affected in gonococcal dermatitis-arthritis syndrome?
Joints - typically few small joints or monoarticular infection of a large joint (knee)
Tenosynovitis - multiple tendons of wrist, fingers, ankles, and toes can be affected
Are blood cultures positive in gonococcal dermatitis-arthritis syndrome?
Not always -> often gonorrhea must be cultured from extraarticular sites such as genitals, rectal area, or pharyngeal sites
What are the characteristics of the pustules in gonococcal dermatitis-arthritis syndrome?
They are few in number, and usually located on the extremities.
Typically painless vesicles or pustules.
How is diagnosis of the etiologic organism of septic arthritis made and how is treatment monitored?
Diagnosis made via blood culture, culture of synovial fluid, or nucleic acid amplification tests / extraarticular sampling if gonococcus is suspected.
Treatment is monitored via ESR / C-reactive protein levels to see if inflammation is falling following antibiotic treatment.
What are the complications of too slowly treating septic arthritis?
Extensive joint destruction with possible osteoarthritis in the future.
Epiphyseal destruction in infants
Growth plate damage in children can lead to deformity / shortening.
Can spread and cause osteomyelitis
What is the treatment for septic arthritis?
IV antibiotics
Closed aspiration of dead cell contents, following response with serial WBCs / cultures
If no resolution with above two: open debridgement and lavage by orthopedics.
