The Atraumatic Knee Effusion: Broadening the Differential ABCs of ...
[Pages:8]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 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
12/12/2015
I have no disclosures.
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.
1
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
56%
D. Knee aspiration
E. Blood work
15%
15%
6% 8%
2
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Knee
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12/12/2015
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.
History of limited use in septic arthritis
Sholter DE et al. "Synovial fluid analysis," in UpToDate last updated Sep 26, 2013. Accessed June 11, 2015.
Margaretten ME, JAMA, 2007.
2
PMH can be useful in septic arthritis
12/12/2015
Some exam is useful in septic arthritis
Sensitivity for septic arthritis
Carpenter CR et al. Acad Emerg Med 2011.
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
86%
Sensitivity and Specificity % for septic arthritis
95, 29 77, 53 26, 98 100, 51 49, 46
2% 4%
6% 3%
Margaretten ME, JAMA, 2007. S e r u m
ES R
>
3 S
0 e
m ru
m m
/h CR S yn
P ov
>1 ia
0 l
0m flu
g/L id W Syn
B o
C v
> ia
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,0 0 id S
0 L y
D n
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v
> ia
2 l
50 flu
U id
/L p
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e
in
> 3 ...
(Specificity, LR, -LR not yet studied.) Carpenter CR et al. Acad Emerg Med 2011.
Aspirate the joint.
WBC count
(+) Likelihood ratio for septic joint
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.
3
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)
12/12/2015
Importance of recognizing and treating septic arthritis
Destroys cartilage within days of onset Inpatients: 7-15% mortality rate even with antibiotic use
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?
55%
A. Borrelia burgdorferi B. Chlamydia trachomatis C. Neisseria gonorrhea D. Staphylococcus aureus E. Mycobacterium tuberculosis
36%
7%
1%
1%
B
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tu b e rc u l...
Margaretten ME, JAMA, 2007.
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.
4
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 2month 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.
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.
12/12/2015
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
64%
18%
10%
4%
4%
R
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a to id
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H LA
A n t i-c y c lic
B -2 7 citru llin
ate
d ... C re
a ctiv e
p ro te in S e d im e n
ta tio n
ra te
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.
5
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.
12/12/2015
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
56% 32%
6%
5%
1%
IB
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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.
6
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 obesity 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.
Crystal search in synovial fluid
Type of crystal
Sensitivity
GOUT (Monosodium urate
crystals)
CPPD (Calcium pyrophosphate
dihydrate crystals)
63-78% 12-83%
Specificity 93-100%
(+) Likelihood
ratio 14
78-96%
2.9
Sholter DE et al. "Synovial fluid analysis," in UpToDate last updated Sep 26, 2013. Accessed June 15, 2015.
12/12/2015
What is the next step?
A. Order serum uric acid
70%
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
26%
bearing if possible
1%
3%
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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)
7
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
12/12/2015
8
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