Joint Pain and Approaches to Arthritis Flashcards
___ are the most common type of joint in the body.
Synovial joints are the most common type of joint in the body.
Three types of joints
Synovial
Fibrous
Cartilagenous
The key feature that distinguishes synovial joints from fibrous and cartilagenous joints is the presence of ____.
The key feature that distinguishes synovial joints from fibrous and cartilagenous joints is the presence of a joint cavity.
Articular capsule
Articular cartilage is always made of ____.
Articular cartilage is always made of hyaline cartilage.
Synovial fluid
“synovia” = thick fluid
A thick, slimy fluid that provides further lubrication in synovial joints. Also nourishes the articular cartilage, which is avascular. Essentially an ultra-filtrate of plasma with some added proteins secereted by synoviocytes, including hyaluronate.
All synovial joints are functionally classified as ____.
All synovial joints are functionally classified as diarthroses.
diarthrosis
A joint which permits free, unrestricted movement
Extrinsic ligament
Located outside the articular capsule of the joint it holds together.
Intrinsic ligament
Fused or incorporated into the articular capsule of the joint which it holds together.
Intracapsular ligament
Ligament which is located inside of the articular capsule of the joint it holds together.
Sagittal knee joint diagram
Articular disc
Fibrocartilagenous structure located inbetween articulating bones. Generally small and oval- or meniscus-shaped. May provide shock absorption.
Sometimes unites bones together and prevents movement, such as at the sternoclavicular joint or the distal radial-ulnar joint.
Bursa
Thin connective tissue filled with lubricating fluid. Located in regions where skin, ligaments, muscles, or muscle tendons can rub against each other, usually near a body joint. Classified based on location relative to the joint.
Subcutaneous bursa
Located between skin and underlying bone. Allows skin to move over bone smoothly.
Submuscular bursa
Found between muscle and underlying bone. Prevents rubbing of the muscle during movements.
Ex, the trochanteric bursa
Subtendinous bursa
Located between tendon and underlying bone.
Articular cartilage
Hypocellular, viscoelastic (due to water and proteoglycan) tissue that lines synovial joints. The articular surface is made of dense collagen of low proteoglycan content.
No basement membrane, innervation, or vascular supply.
During gentle walking, the force experienced by the hip joint is roughly equivalent to ___.
During gentle walking, the force experienced by the hip joint is roughly equivalent to 4 times the body weight of the individual.
What happens to the articular cartilage during loading?
Water exudes from proteoglycans and mixes with hyalonurate-rich synovial fluid.
The resulting coeffient of friction produced by this process is 1/5 that of the smooth ice-smooth ice coefficient of friction.
The integrity of the articular cartilage matrix is maintained by ___.
The integrity of the articular cartilage matrix is maintained by chondrocytes.
Articular cartilage is bound to the underlying bone through ____.
Articular cartilage is bound to the underlying bone through a narrow calcified zone of cartilage.
High loading of a healthy joint is unlikely alone to ____
High loading of a healthy joint is unlikely alone to initiate joint disease
Disuse of a joint leads to ___.
Prolonge ___ may even lead to ___.
Disuse of a joint leads to atrophy of the articular cartilage.
Prolonged atrophy may even lead to replacement of the articular cartilage with fibro-fatty tissue.
All connective tissues, including cartilage, respond to ___.
All connective tissues, including cartilage, respond to the mechanical forces placed upon them and, in general, extra use leads to hypertrophy and mechanical strengthening
Synovial membrane
1-3 cells thick. Forms the surface layer of the synovial tissue, but is otherwise not particularly distinct from it.
Deep synovial tissue is made up of . . .
- Many vascular vessels
- Many fat-rich cells
- Low cell count outside of a discontinuous layer of synovial intimal (aka synoviocytes) cells on the internal joint surfaces
- Synoviocytes line all surfaces apart from cartilage and menisci
- Aspiratable volume of only 0-4 mL of fluid
Changes in the loading-capability of one joint have effects on ___.
Changes in the loading-capability of one joint have effects on the loading-capability of other joints.
Hyaluronate
Produced by synoviocytes. Present in synovial fluid.
A linear, repeating disaccharide of β-D-gluconuryl-β-D-N-acetyl-glucosamine. Very high molecular weight, greater than 10 megadaltons.
Forms the central axis of the proteoglycan aggregates in synovial fluid which provides integrity to articular cartilage and other extracellular matrices of the synovium.
It is the main component responsible for synovial fluid’s visco-elastic properties.
How fluid accumulates in the synovium
The synovium has a high osmotic potential as a result of all of the proteins, proteoglycans, and carbohydrates secreted into it by synoviocytes.
Synovium in rheumatoid arthritis
Undergoes massive hyperplasia to form a complex, villous structure extending into the synovial space, a thickened cell lining layer, and infiltration of many leukocytes which then form lymphoid follicles.
Acute inflammation of the synovium can result in proteolytic cleavage of the articular cartilage and intracapsular ligaments. Inflammatory cytokines also activate ostoclasts to resorb bone, causing the bone erosion characteristic of RA.
Basic clinical characterization of arthritis
- Is it true arthritis? Or is it extra-articular? (Bursitis, etc)
- Inflammatory or Non-inflammatory?
- Duration (acute, subacute, or chronic?)
- Number of joints (if multiple, is it symmetrical?)
- Accurate delineation of involved joints
Synovial fluid WBC count is ___ in non-inflammatory arthritis and ___ in inflammatory arthritis. This is evaluated by ___.
Synovial fluid WBC count is <2000 /μLin non-inflammatory arthritis and>2000 / μLin inflammatory arthritis. This is evaluated byarthrocentesis.
Patients with an inflammatory arthritis usually complain of. . .
. . . pain and stiffness in involved joints; typically these symptoms are worse in the morning or after periods of inactivity and improve with mild to moderate activity.
Patients with non-inflammatory arthritis have pain that ___, with ___ stiffness.
. . . worsens with activity and improves with rest, with mild (<30 minutes in the morning) stiffness.
Constitutional symptoms in arthritis
- Fever: raises possibility of arthritis due to infection, but is not totally specific.
- Constitutional symptoms rarely ever accompany non-inflammatory arthritis.
Family history in arthritis
- Positive family history increases likelihood of certain forms of arthritis
- Ankylosing spondylitis especially (~75 fold risk of general pop.)
- Systemic lupus erythematosus (~20-30 fold risk of general pop.)
- Less helpful for rheumatoid arthritis (~3 fold risk of general pop.)
- Osteoarthritis is often misdiagnosed as rheumatoid arthritis due to confounding with family history of rheumatoid arthritis.
Extra-articular manifestations in arthritis
- Kidney abnormalities, pulmonary abnormalities, oral ulcerations, ocular inflammation, peripheral neuropathy
- Presence of rash
- May signal that the arthritis is due to systemic rheumatic disease or vasculitis
Essential features of acute monoarthritis
- Septic arthritis is the marajor diagnostic concern
- Arthrocentesis is the most important diagnostic test
Acute arthritis
- Except in cases of trauma, acute arthritis is usually inflammatory
- Septic and crystal arthritis have acute onset
- History is very helpful differentiating
Acute monoarthritis differential
- Septic arthritis
- Crystal arthritis
- Trauma-induced arthritis
- Joint-space infection
___ is the foremost concern in patients with acute pain and swelling in a single joint not clearly due to trauma.
Infection is the foremost concern in patients with acute pain and swelling in a single joint not clearly due to trauma.
Laboratory evaluation for acute monoarthritis
- Indicated for all unexplained cases
- Arthrocentesis: Send synovial fluid for
- Culture
- WBC count
- Gram stain
- Examination for crystals by polarized light microscopy
Synovial fluid WBC count >50,000/μL
Likely septic arthritis, possibly crystal arthritis
Synovial fluid WBC count <50,000/μL, but >2,000/μL
Likely crystal arthritis
Gram stain for bacteria in arthrocentesis
False negatives are high (25-50%), and so false negatives do not exclude bacterial arthritis
Also, finding of crystals does not exclude infection. They may occur simultaneously.
Essential features of chronic arthritis
- Distinguishing inflammatory from non-inflammatory etiology is key
- Rheumatoid and osteoarthritis are the leading causes
- Careful delineation of joints involved is key
Imaging for acute arthritis
May be useful to locate fractures in traumatic monoarticular arthritis, but of little utility with no history of trauma, if the process is truly acute.
More likely to be misleading for acute, nontraumatic monoarticular arthritis.
___ is the leading cause of chronic noninflammatory monoarthritis,
Osteoarthritis is the leading cause of chronic noninflammatory monoarthritis,
Especially when the hip, knee, first carpometacarpal joint, or acromioclavicular joint is involved
Chronic arthritis differential
Chronic polyarthritis of the hand
- Radiographs are indicated at time of presentation
- May show primary generalized osteoarthritis, calcium pyrophosphate deposition (pseudogout), or chronic tophaceous gout
- Delayed/late imaging of rheumatoid arthritis or spondylarthropathies may also show changes on radiograph
Psoriatic arthritis typically involves ___ joints.
Psoriatic arthritis typically involves DIP joints.
Factors that make laboratory tests for rheumatic disease difficult
- They share many characteristic inflammatory markers with other inflammatory diseases, infection, and malignancies
- Prevalence of certain rheumatic diseases is low in most populations, so even if sensitivity and specificity of a test are high, positive predictive value may be low.
Osteoarthritis and rheumatoid arthritis have ____.
Osteoarthritis and rheumatoid arthritis have different patterns of joint involvement.
Osteo: DIPs, PIPs, first metacarpal, but NOT MCPs, wrists, elbows, ankles
Rheumatoid: PIPs, MCPs, and the wrist, but NOT DIPS or thoracid and lumbosacral spine
Both may affect large joints like the hip and knee
Laboratory Tests for Arthritis
- ELISA or other immunspecific test for autoantibodies
- Acute phase response-mediator measurement (CRP or ESR)
- CRP: Measure serum CRP as a proxy for IL-6, IL-1, TNF, etc
- ESR: erythrocyte sedimentation rate, effectively measures blood fibrinogen levels
CRP levels
- Increase with infection (specifically acute phase, peaks 48 hr, declines within 18 hours following)
- Increase with age
- Increase with BMI
- Can suggest inflammatory process, but is quite nonspecific within that category
- Still, may be a useful indicator of progression of certain autoinflammatory diseases such as rheumatoid arthritis
Erythrocyte sedimentation rate
- Allow anticoagulated blood to sediment for 1 hr in a glass tube
- Reference range: 0-10 mm/hr in males, 0-15 mm/hr in females
- Upper limits of normal range increase with age and BMI
- Effectively a measure of fibrinogen and other proteins that act as part of the acute phase response to increase sedimentation/coagulability.
- Has a slower rate of increase following acute phase induction than CRP
- May be influenced by conditions other than acute phase response (anything that increases coagulability: pregnancy, anemia, kidney disease, obesity, hypercholesterolemia)
Likely cause of joint pain in a patient with a history of. . .
Trauma: ___
Overuse: ___
Inflammation: ___
Likely cause of joint pain in a patient with a history of. . .
Trauma: could be any really, but this is the one case in which bone fracture may be involved
Overuse: Bursitis or tendonitis
Inflammation: Bursitis, synovitis, tendonitis
Cutaneous distribution of C5, C6, C7, and C8 spinal nerves
Osteoarthritic cartilage
Note: The mechanical damage to the cartilage (frayed surface), the hypertrophy of the chondrocytes, and the lack of inflammatory cells
The majority of white blood cells present in rheumatoid arthritis arthrocentesis will be . . .
. . . neutrophils.
This is another difference between osteoarthritis and rheumatoid arthritis.
A parient presents with arthritis. It is unclear from history and physical exam whether it is osteoarthritic or rheumatoid arthritic in origin. You take an aspirate sample and do a WBC count. The count comes back as exactly 2,000 per μL, with 20% PMN. What is the likely diagnosis?
The 2,000 per μL is not particularly helpful, but the low PMN content suggests that this is an osteoarthritic process, as rheumatoid WBC infiltrate is usually neutrophil predominant.
Findings of osteoarthritis on X-ray
- Joint space narrowing
- Sclerosis (Increase in density of bones on articular surface)
- Osteophytes (outcroppings of bone that are not usually there)
Findings of rheumatoid arthritis on X-ray
Bone erosion
Major clinical features that distinguish arthritis from arthralgia
Swelling and heat
Ulnar styloid
The bony prominence of the ulna at the wrist joint
Thresholds for non-inflammatory / inflammatory / infectious joint disease
Noninflammatory < 2000 < Inflammatory < 50,000 < Infectious
Sensitivity of the ~50,000 cutoff for inflammatory vs infectious for infectious diseases
60%
Know that these are just rules of thumb, they are not hard proof!
Good questions for any patient presenting with idiopathic arthritis
- Have you observed any rashes? (Slapped cheek for parvovirus, erythema migrans for lyme, psoriasis for psoriatic arthritis)
- Did you have any signs of fever prior to or following your arthritic symptoms? (Screen for infectious and inflammatory arthritis)
- Is the arthritis constant or does it flare at certain times? (Screen for crystal arthropathy)
- Do you have any morning stiffness? If so, for how long? (Screen for and differentiate rheumatoid and osteoarthritis)
- Have you recently had any new sexual partners? (Screen for reactive or gonococcal arthritis)
Reactive arthritis
Reaction to Chlamydia resulting in autoimmune inflammation of joints and bladder
When you say gout is “negatively birefringent,” this means that it appears ____ under parallel polarized light and ____ under perpendicular polarized light.
When you say gout is “negatively birefringent,” this means that it appears yellow under parallel polarized light and blue under perpendicular polarized light.
When you say pseudogout is “positively birefringent,” this means that it appears ____ under parallel polarized light and ____ under perpendicular polarized light.
When you say pseudogout is “positively birefringent,” this means that it appears blue under parallel polarized light and yellow under perpendicular polarized light.
Crepitus
“cracking sensation” when moving a joint. Typical symptom of osteoarthritis.
Chondrocalcinosis
Radiologic finding of calcium deposition within the articular cartilage. Characteristic of pseudogout.
