Monoarticular Arthritis

Question 1

Differential Diagnosis

Answer 1

Trauma (IE, hemarthrosis, Fx), infection (Lyme, staph>strep>GNR, fungal mycobacterial), avascular necrosis; also consider causes of oligo- or polyarticular arthritis (crystal-induced, OA, RA, seronegative spondyloarthropathies, sarcoid, etc); causes of monoarthritis can coexist, infection must always be r/o before treating other causes

Question 2

Bursitis

Answer 2

Inflammation/injury of bursa (protect bony prominences) secondary to degeneration, infection, injury, crystals, RA; p/w pain on motion/rest, swelling, focal tenderness =/- decrease ROM; EtOH, DM, immunosuppression are risk factors for septic bursitis

Question 3

Septic Arthritis

Answer 3

Hip and knee»wrist, ankle; risk factors include immunosuppression, IVDU, malignancy, prosthetic joints, RA, renal failure, increase age, skin, infection, steroid inj; early diagnosis and treatment key due to mortality (7-15%) and risk of joint destruction

Question 4

Gonococcal

Answer 4

Acute onset in sexually active young adult w/o hx trauma; may p/w polyarthralgias, skin lesions, tenosynovitis or purulent arthritis w/o skin lesions

Question 5

History

Answer 5

Chronicity, hx trauma or prior joint pain/swelling; sexual hx (gonococcal): EtOH/red meat/shellfish intake (crystals); travel (lyme, infectious); comorbidities (increase risk for septic arthritis in pts w/RA, prosthetic joints, DM); anticoagulant use; bleeding d/o (increases risk of hemarthrosis); IVDU (septic)

Question 6

Extra-articular manifestations

Answer 6

Fevers/chills (septic arthritis), GI illness (reactive arthritis, IBD-assoc arthritis), genital pain/lesions (gonococcal), rash (psoriasis, lupus, viral exanthems, Lyme erythema migrans), oral ulcers (SLE), inflammatory eye disease (seronegative spondyloarthropathies, RA)

Question 7

Exam

Answer 7

Warmth, redness, effusion, joint line tenderness, bony crepitation w/flexion, rash or break in skin, soft tissue swelling, tophi; assess for extraarticular disease

Question 8

Range of Motion

Answer 8

Decrease active ROM w/ preserved passive ROM suggests soft tissue cause; limited active and passive ROM more likely joint involvement; significant pain w/minimal ROM concerning for septic arthritis

Question 9

Workup

Answer 9

Arthrocentesis most important test (cell count w/diff, gram stain, crystals, Cx): radiograph can be useful to assess for fracture (hx trauma) or chondrocalcinosis (seen in CPDD), erosions (seen in RA, gout, osteomyelitis); BCx if septic arthritis suspected: ESR, CRP, uric acid

Question 10

Bursitis

Answer 10

Aspiration of fluid for Cx, cell count, crystals, deep bursal infections may be imaged w/MRI or u/s

Question 11

Synovial Fluid Analysis

NI

Answer 11

Color: clear
Clarity: clear
WBC: <200
PMNS %: <25
Cx: -

Question 12

Synovial Fluid Analysis

Noninflammatory

Answer 12

Color: yellow
Clarity: clear
WBC: 0-1000
PMNS %: <25
Cx: -

Question 13

Synovial Fluid Analysis

Inflammatory

Answer 13

Color: Yellow
Clarity: clear-opaque
WBC: 1K-100K
PMNS %: >50
Cx: -

Question 14

Synovial Fluid Analysis

Septic

Answer 14

Color: Yellow/green
Clarity: opaque
WBC: 15K-100K
PMNS %: >75
Cx: Often +

Question 15

Septic arthritis treatment

Answer 15

ED/admission for empiric abx and orthopedics eval

Question 16

Hemarthrosis treatment

Answer 16

Analgesics, aspiration/injection, compression sleeve to prevent reaccumulation, assessment for bleeding d/o

Question 17

Bursitis treatment

Answer 17

Avoid activities that increase pain, joint protection, NSAIDs, ice, heat, PT; intrabursal steroid injection in refractory cases