12/12/2015

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The Atraumatic Knee Effusion: Broadening the Differential ABCs of Musculoskeletal Care

Carlin Senter, MD Primary Care Sports Medicine Departments of Medicine and Orthopaedics

December 12, 2015

Objectives Case #1 At the end of this lecture you will know… 1. The differential diagnosis for a patient with atraumatic A 25 y/o woman presents with 2 weeks of increasingly painful monoarticular arthritis. atraumatic swelling of her left knee.
2. The keys to working this patient up No locking
1. Knee aspiration and interpretation No instability
No fever or night sweats 2. Labs
No recent GI or GU illness.
Sexually active with one partner x 1 month. Exam: Difficulty bearing weight on the L leg, large L knee effusion, diffuse tenderness of the L knee, limited passive range of motion L knee due to pain, knee feels warm to touch. No skin erythema.

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What would you do next? Differential monoarticular arthritis
Noninflammatory
Septic • Osteoarthritis • Bacteria (remember gonorrhea, A. 2 week trial of NSAIDs + hydrocodone/APAP for breakthru pain Lyme disease) • Neuropathic arthropathy B. 2 week trial of NSAIDs + physical therapy • Mycobacteria
Inflammatory C. Knee x-rays 56% • Fungus • Crystal arthropathy D. Knee aspiration
Hemorrhagic ‒ Gout (Monosodium urate crystals) E. Blood work • Hemophilia ‒ CPPD (Calicium pyrophosphate dihydrate crystals, aka pseudogout) • Supratherapeutic INR • Spondyloarthritis (involves low • Trauma 15% 15% back, but can be peripheral only, also can affect entheses) • Tumor 6% 8% ‒ Reactive arthritis (used to be called Reiter’s syndrome) ‒ Psoriatic arthritis

. . i o n . - r a y s ‒ IBD-associated s + . . . s + D I l o o d w o r k A K n e e x B NS e e a s p i r a t f n • Rheumatoid arthritis, Systemic o f N S A I D o K i a l lupus erythematosus e k t r i a l e k t r e e 2 w 2 w Johnson MW. Acute knee effusions: a systematic approach to diagnosis. Am Fam Physician. 2000 Apr 15;61(8):2391-400.

History of limited use in septic arthritis

Sholter DE et al. “Synovial fluid analysis,” in UpToDate last updated Sep 26, 2013. Margaretten ME, JAMA, 2007. Accessed June 11, 2015.

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PMH can be useful in septic arthritis Some exam is useful in septic arthritis

Sensitivity for septic arthritis

(Specificity, LR, -LR not yet studied.)

Carpenter CR et al. Acad Emerg Med 2011. Carpenter CR et al. Acad Emerg Med 2011.

What’s the most specific lab test for septic Aspirate the joint. arthritis? A. Serum ESR >30mm/h WBC count <25,000 25,000 50,000 100,000
Sensitivity and Specificity % B. Serum CRP >100mg/L
for septic arthritis (+) 0.32 2.9 7.7 28 C. Synovial fluid WBC >100,000
95, 29 Likelihood D. Synovial fluid LDH > 250 U/L ratio for
E. Synovial fluid protein > 3.0g/dL 77, 53 septic joint 86%
26, 98  PMNs > 75% bacterial infection
100, 51  Eosinophils in fluid parasitic infection, allergy, neoplasm, or Lyme disease
49, 46

If suspect gonococcal arthritis, cultures in synovial fluid (+) in < 50% of cases. 4% 6% 2% 3% Yield increased if plates of chocolate agar or Thayer-Martin medium

L inoculated at the bedside. Also check blood cultures. U/ m m / h 0 0 0 m g / L 5 1 2 > 3 0 > e i n > 3 . . . R t S R P C L D H > d d p r o r u m E l u i e l f S S e r u m i a v y n o Margaretten ME, JAMA,Synovial fluid 2007.WS BC >100,000 Synovial flui

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If concern for septic arthritis the joint must be Importance of recognizing and treating septic aspirated emergently arthritis

Aspirate in clinic OR
Destroys cartilage within days of onset
Call orthopaedics with emergent consult.
Inpatients: 7-15% mortality rate even with antibiotic use
Insist on exam and consideration of aspiration within hours
Septic joint needs emergent wash-out in OR (sometimes bedside serial lavage)

Margaretten ME, JAMA, 2007.

The knee aspirate contains 50,000 WBCs, 80% Disseminated gonococcal infection (DGI) PMNs. There are no crystals. Gram stain is pending. What is the most likely organism in this
Mostly starts with asymptomatic patient’s case? 55% mucosal infection
A. Borrelia burgdorferi Rarely preceded by symptomatic genital infection B. Chlamydia trachomatis 36%
2 syndromes possible C. Neisseria gonorrhea D. Staphylococcus aureus 1. Tenosynovitis + dermatitis E. Mycobacterium tuberculosis 7% 2. Purulent arthritis without 1% 1% dermatitis

r i s a e e u s .. r r h r e o r c u l . g d o r f n s a u r u b u o c c t u b e a ia trachom ati c m l o i u y d i s s e r i a g o r e B o r r e l i l a m N c t e h t a p h y a C S b c o M y Goldenberg DL, “Disseminated gonococcal infection,” UpTo Date last updated July 30, 2014. Accessed June 7, 2015.

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Case #2 Which of the following labs is not recommended in her case? 30 y/o woman presents to your clinic with seven weeks of R knee A. Rheumatoid factor swelling with no injury. On review of systems, she endorses a 2- B. HLA B-27 64% month history of finger joint pain and swelling bilaterally. C. Anti-cyclic citrullinated peptide On exam you find that 3 of the MCP joints on the R hand are D. C reactive protein swollen and tender. The R knee has an effusion. E. Sedimentation rate

18% 10% 4% 4%

n e - 2 7 . a t B .. r d H L A t a t i o n n active protei r e i m e citrullinate C d Rheum atoid factor S e c l i c - c y t i n A

2010 ACR classification criteria for rheumatoid Caveats to ACR rheumatoid arthritis criteria arthritis
Synovitis in at least 1 joint and Lack of alternative dx and ≥ 6 of the
following: Seronegative RA
Joint involvement • Population of RA patients without RF or anti-CCP antibodies • 2-10 large joints = 1 point
Disease < 6 weeks • 1-3 small joints = 2 points • If all other testing points to RA then can be diagnosed at < 6 • 4-10 small joints = 3 points weeks • > 10 joints = 5 points
Inactive RA
RF or anti-CCP abnormal • After treatment the labs may normalize but RA can be diagnosed • Low positive = 2 points based on past findings • High positive = 3 points
Increased ESR or CRP = 1 point
Symptoms ≥ 6 weeks = 1 point

UpToDate: “Diagnosis and differential diagnosis of rheumatoid arthritis,” UpToDate: “Diagnosis and differential diagnosis of rheumatoid arthritis,” accessed June 7, 2015. accessed June 7, 2015.

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Case #3 You aspirate her knee and find the following:

A 25 y/o woman presents with 2 weeks of increasingly painful
20,000 WBCs atraumatic swelling of her left knee.
50% PMNs
No locking
No crystals
No instability

No fevers Gram stain negative

Diagnosed with gastroenteritis 3 weeks ago, now resolved. Culture pending
Sexually active, in monogamous relationship x 6 months. Exam: Difficulty bearing weight on the L leg, large L knee effusion, diffuse tenderness of the L knee, pain with passive L knee range of motion, range of motion limited to 10-90 degrees.

What is the most likely diagnosis? Reactive arthritis is a clinical diagnosis 1. Musculoskeletal findings 1. Asymmetric joint swelling +/- enthesitis +/- dactylitis +/- inflammatory back pain A. IBD-associated arthritis 2. Infection preceded the musculoskeletal findings 56% B. Reactive arthritis 1. Diarrhea C. Systemic lupus erythematosus 2. Urethritis (chlamydia trachomatis) D. Rheumatoid arthritis 3. No other obvious cause for symptoms 32% 1. Check labs and fluid to r/o gout, rheumatoid arthritis, lupus, Lyme disease, E. Pseudogout septic arthritis 1. Stool culture if active diarrhea 2. Urine or vaginal swab for Chlamydia in asymptomatic or those with urethritis 6% 5% 1% 2. Consider xray to r/o osteoarthritis, stress fracture 3. Perform arthrocentesis if effusion present

s s
i . t i s 1. Cell count, differential expect inflammatory picture r i t i r i t r i a . . h t h r t h m a r e a r t 2. Crystals t e d r y t h P s e u d o g o u t a e t o i d i s a c u 3. Gram statin, culture s s o R e a c t i v e a p u m a u e D- R h I B y s t e m i c l S Yu DT from UpToDate, “Reactive arthritis,” last updated May 15, 2015. Accessed June 7, 2015.

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Case #4 What is the next step?

A 60 y/o woman presents with swelling of her right knee. The pain A. Order serum uric acid started when she woke up 3 days ago and is severe. She has 70% obesity and takes hydrochlorothiazide for hypertension. Her B. Order 24-hour urine uric acid creatinine is 1.0 mg per deciliter. The night before this started she C. Aspirate the knee effusion, send for cell was on her feet for hours cooking a risotto with sweetbreads which she paired with a craft beer. count + differential, crystals, gram stain, culture D. Order R knee xrays, 3 views, weight 26% bearing if possible 1% 3%

d . . .. i o . . w . a c i c i e c r i v r i u 3 u e n m r i y s , u n e e e f f u s r a e r u r k x s u o e t h e n e 4 - h k O r d e r e r 2 e r R O r d A s p i r a t e O r d

Crystal search in synovial fluid Gout facts

Type of crystal Sensitivity Specificity (+) Men:women = 3-4: 1 Likelihood • Sex difference decreases with age ratio  GOUT 63-78% 93-100% 14 • Lower estrogen less uric acid excretion (Monosodium urate
Risk factors crystals) CPPD 12-83% 78-96% 2.9 • Eating food rich in purines (Calcium pyrophosphate • Alcohol dihydrate crystals) • Soft drinks • Fructose
Consider aspirating knees of your knee OA patients if they have a new pattern of swelling/pain (may be crystal arthropathy)

Sholter DE et al. “Synovial fluid analysis,” in UpToDate last updated Sep 26, 2013. Accessed June 15, 2015.

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Objectives At the end of this lecture you will know…

1. The differential diagnosis for a patient with atraumatic monoarticular arthritis. 2. The keys to working this patient up 1. Knee aspiration and interpretation 2. Labs

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