The Atraumatic Knee Effusion: Broadening the Differential ABCs of - - PowerPoint PPT Presentation

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The Atraumatic Knee Effusion: Broadening the Differential

Carlin Senter, MD Primary Care Sports Medicine Departments of Medicine and Orthopaedics December 12, 2015

ABCs of Musculoskeletal Care

I have no disclosures. 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

Case #1

A 25 y/o woman presents with 2 weeks of increasingly painful atraumatic swelling of her left knee. No locking No instability No fever or night sweats 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?

A. 2 week trial of NSAIDs + hydrocodone/APAP for breakthru pain B. 2 week trial of NSAIDs + physical therapy

• C. Knee x-rays
• D. Knee aspiration

E. Blood work

2 week trial of NSAIDs + ... 2 week trial of NSAIDs + ... Knee x-rays Knee aspiration Blood work

6% 8% 15% 56% 15%

Differential monoarticular arthritis

Noninflammatory

• Osteoarthritis
• Neuropathic arthropathy

Inflammatory

• Crystal arthropathy

‒ Gout (Monosodium urate crystals) ‒ CPPD (Calicium pyrophosphate dihydrate crystals, aka pseudogout)

• Spondyloarthritis (involves low

back, but can be peripheral only, also can affect entheses)

‒ Reactive arthritis (used to be called Reiter’s syndrome) ‒ Psoriatic arthritis ‒ IBD-associated

• Rheumatoid arthritis, Systemic

lupus erythematosus

Septic

• Bacteria (remember gonorrhea,

Lyme disease)

• Mycobacteria
• Fungus

Hemorrhagic

• Hemophilia
• Supratherapeutic INR
• Trauma
• Tumor

Johnson MW. Acute knee effusions: a systematic approach to diagnosis. Am Fam

• Physician. 2000 Apr 15;61(8):2391-400.

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

History of limited use in septic arthritis

Margaretten ME, JAMA, 2007.

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PMH can be useful in septic arthritis

Carpenter CR et al. Acad Emerg Med 2011.

Some exam is useful in septic arthritis

(Specificity, LR, -LR not yet studied.) Carpenter CR et al. Acad Emerg Med 2011. Sensitivity for septic arthritis

What’s the most specific lab test for septic arthritis?

A. Serum ESR >30mm/h B. Serum CRP >100mg/L C. Synovial fluid WBC >100,000 D. Synovial fluid LDH > 250 U/L E. Synovial fluid protein > 3.0g/dL

Sensitivity and Specificity % for septic arthritis

95, 29 77, 53 26, 98 100, 51 49, 46

Margaretten ME, JAMA, 2007.

S e r u m E S R > 3 m m / h S e r u m C R P > 1 m g / L S y n

• v

i a l f l u i d W B C > 1 , S y n

• v

i a l f l u i d L D H > 2 5 U / L S y n

• v

i a l f l u i d p r

• t

e i n > 3 . . .

2% 4% 3% 6% 86%

Aspirate the joint.

WBC count <25,000 25,000 50,000 100,000 (+) Likelihood ratio for septic joint 0.32 2.9 7.7 28

PMNs > 75% bacterial infection Eosinophils in fluid parasitic infection, allergy, neoplasm, or Lyme disease If suspect gonococcal arthritis, cultures in synovial fluid (+) in < 50% of cases. Yield increased if plates of chocolate agar or Thayer-Martin medium inoculated at the bedside. Also check blood cultures.

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If concern for septic arthritis the joint must be aspirated emergently

Aspirate in clinic OR Call orthopaedics with emergent consult. Insist on exam and consideration of aspiration within hours Septic joint needs emergent wash-out in OR (sometimes bedside serial lavage)

Importance of recognizing and treating septic arthritis

Destroys cartilage within days of onset Inpatients: 7-15% mortality rate even with antibiotic use

Margaretten ME, JAMA, 2007.

The knee aspirate contains 50,000 WBCs, 80%

• PMNs. There are no crystals. Gram stain is
• pending. What is the most likely organism in this

patient’s case?

A. Borrelia burgdorferi B. Chlamydia trachomatis C. Neisseria gonorrhea D. Staphylococcus aureus E. Mycobacterium tuberculosis

B

• r

r e l i a b u r g d

• r

f e r i C h l a m y d i a t r a c h

• m

a t i s N e i s s e r i a g

• n
• r

r h e a S t a p h y l

• c
• c

c u s a u r e u s M y c

• b

a c t e r i u m t u b e r c u l . . .

1% 7% 1% 36% 55%

Disseminated gonococcal infection (DGI)

Mostly starts with asymptomatic mucosal infection Rarely preceded by symptomatic genital infection 2 syndromes possible 1. Tenosynovitis + dermatitis 2. Purulent arthritis without dermatitis

Goldenberg DL, “Disseminated gonococcal infection,” UpTo Date last updated July 30, 2014. Accessed June 7, 2015.

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Case #2

30 y/o woman presents to your clinic with seven weeks of R knee swelling with no injury. On review of systems, she endorses a 2- month history of finger joint pain and swelling bilaterally. On exam you find that 3 of the MCP joints on the R hand are swollen and tender. The R knee has an effusion.

Which of the following labs is not recommended in her case?

A. Rheumatoid factor B. HLA B-27 C. Anti-cyclic citrullinated peptide D. C reactive protein E. Sedimentation rate

R h e u m a t

• i

d f a c t

• r

H L A B

• 2

7 A n t i

• c

y c l i c c i t r u l l i n a t e d . . . C r e a c t i v e p r

• t

e i n S e d i m e n t a t i

• n

r a t e

4% 64% 10% 4% 18%

2010 ACR classification criteria for rheumatoid arthritis

Synovitis in at least 1 joint and Lack of alternative dx and ≥ 6 of the following: Joint involvement

• 2-10 large joints = 1 point
• 1-3 small joints = 2 points
• 4-10 small joints = 3 points
• > 10 joints = 5 points

RF or anti-CCP abnormal

• Low positive = 2 points
• High positive = 3 points

Increased ESR or CRP = 1 point Symptoms ≥ 6 weeks = 1 point UpToDate: “Diagnosis and differential diagnosis of rheumatoid arthritis,” accessed June 7, 2015.

Caveats to ACR rheumatoid arthritis criteria

Seronegative RA

• Population of RA patients without RF or anti-CCP antibodies

Disease < 6 weeks

• If all other testing points to RA then can be diagnosed at < 6

weeks Inactive RA

• After treatment the labs may normalize but RA can be diagnosed

based on past findings

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

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Case #3

A 25 y/o woman presents with 2 weeks of increasingly painful atraumatic swelling of her left knee. No locking No instability No fevers Diagnosed with gastroenteritis 3 weeks ago, now resolved. 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.

You aspirate her knee and find the following:

20,000 WBCs 50% PMNs No crystals Gram stain negative Culture pending

What is the most likely diagnosis?

A. IBD-associated arthritis B. Reactive arthritis C. Systemic lupus erythematosus D. Rheumatoid arthritis E. Pseudogout

I B D

• a

s s

• c

i a t e d a r t h r i t i s R e a c t i v e a r t h r i t i s S y s t e m i c l u p u s e r y t h e m a . . . R h e u m a t

• i

d a r t h r i t i s P s e u d

• g
• u

t

32% 56% 5% 1% 6%

Reactive arthritis is a clinical diagnosis

1. Musculoskeletal findings 1. Asymmetric joint swelling +/- enthesitis +/- dactylitis +/- inflammatory back pain 2. Infection preceded the musculoskeletal findings 1. Diarrhea 2. Urethritis (chlamydia trachomatis) 3. No other obvious cause for symptoms 1. Check labs and fluid to r/o gout, rheumatoid arthritis, lupus, Lyme disease, septic arthritis 1. Stool culture if active diarrhea 2. Urine or vaginal swab for Chlamydia in asymptomatic or those with urethritis 2. Consider xray to r/o osteoarthritis, stress fracture 3. Perform arthrocentesis if effusion present 1. Cell count, differential expect inflammatory picture 2. Crystals 3. Gram statin, culture

Yu DT from UpToDate, “Reactive arthritis,” last updated May 15, 2015. Accessed June 7, 2015.

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Case #4

A 60 y/o woman presents with swelling of her right knee. The pain started when she woke up 3 days ago and is severe. She has

• besity and takes hydrochlorothiazide for hypertension. Her

creatinine is 1.0 mg per deciliter. The night before this started she was on her feet for hours cooking a risotto with sweetbreads which she paired with a craft beer.

What is the next step?

A. Order serum uric acid B. Order 24-hour urine uric acid C. Aspirate the knee effusion, send for cell count + differential, crystals, gram stain, culture D. Order R knee xrays, 3 views, weight bearing if possible

O r d e r s e r u m u r i c a c i d O r d e r 2 4

• h
• u

r u r i n e u r i c . . . A s p i r a t e t h e k n e e e f f u s i

• .

. O r d e r R k n e e x r a y s , 3 v i e w . .

26% 3% 70% 1%

Crystal search in synovial fluid

Type of crystal Sensitivity Specificity (+) Likelihood ratio GOUT (Monosodium urate crystals) 63-78% 93-100% 14 CPPD (Calcium pyrophosphate dihydrate crystals) 12-83% 78-96% 2.9 Sholter DE et al. “Synovial fluid analysis,” in UpToDate last updated Sep 26, 2013. Accessed June 15, 2015.

Gout facts

Men:women = 3-4: 1

• Sex difference decreases with age
• Lower estrogen less uric acid excretion

Risk factors

• Eating food rich in purines
• Alcohol
• Soft drinks
• Fructose

Consider aspirating knees of your knee OA patients if they have a new pattern of swelling/pain (may be crystal arthropathy)

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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