Approach to Joint Pain - Diagnostic Framework



1) Chronicity

2) Inflammatory vs Non-Inflammatory

3) Number of Joints Involved



1) Chronicity:

 • Acute - Think about bacterial infections (bacterial), acute rheumatic fever

 • Chronic - Think about indolent infections (gonorrhea, Lyme, mycobacterial), RA, crystal disease, spondyloarthropathies, lupus, OA



2. Inflammatory vs. Non-inflammatory:

 • Inflammatory - AM stiffness, warm, swollen, tender

 • Non-inflammatory - No AM stiffness, weight-bearing joints, cool à Osteoarthritis typically non-inflammatory!



3. Number of Joints Involved:

Monoarticular (1 joint):

	• Septic joint (bacterial, gonococcal, Lyme), reactive arthritis, gout or pseudogout, OA *Always do arthrocentesis! Send for cell count, culture, look for crystals.

	• WBC <2k: Noninflammatory

	• Bloody: Trauma, coagulopathy, tumor

	• Non-bloody: OA, avascular necrosis, Charcot (DM2, syphilis, alcohol - peripheral neuropathy so trauma and joint destruction lower limbs)

	• WBC 2-20k: Inflammatory, crystalline disease, seronegative spondyloarthropathies

	• WBC >20k: Septic joints with bacterial infection, needs washout!

	• Key point: If that patient had a prosthetic joint that was placed >30d ago = Worry about late prosthetic joint infection. This may be a more indolent presentation with lower WBC cutoff... >10K is concerning as there may be biofilm-forming organisms



Oligoarticular (<5 joints):

	• Spondyloarthropathies, gout, pseudogout, gonorrhea, Lyme, OA. Like in this case, you can also get bacterial seeding of multiple joints if bacteremic.



Polyarticular (5+ joints):

	• Symmetric vs. non-symmetric.

	• Acute = Viral - parvovirus, HIV, hepatitis, herpes

	• Chronic = RA, SLE, psoriatic arthritis



Crystals:

	• Rhomboid, blue = pseudogout

	• Parallel, yellow = gout 

	(memory trick: remember yellow and allopurinol both have a double L!)



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