Diseases (12)

Diagnostic Testing (12)


Reflex to culture if elevated WBC and no crystals or bacteria are seen.


If joined inflammation and aspiration required.


If arthritis present


If joints are involved.


If arthritis present are involved.


If obtained, the synovial fluid in Neuropathic arthropathy is clear, sterile and lack crystals.


Synovial fluid analysis is utilized to diagnose the cause of pain, swelling, and fluid collection in the joints. The joints that are most commonly affected are the knee, hip, and shoulder joints. The conditions that affect the synovial fluid can be broken down into five general categories. These disease categories are Non-Inflammatory disease, Inflammatory disease, Infectious disease, Degenerative disease, and Bleeding disorders. Non-inflammatory diseases that are associated with synovial fluid involvement include trauma, sickle cell disease, and CPPD crystal deposition disease (pseudogout). Inflammatory diseases associated with synovial fluid include autoimmune disorders such as systemic lupus erythematosus, psoriasis, and rheumatoid arthritis as well as gout. Infectious arthritis is usually acute bacterial in nature. The most common causative organism in some studies is Neisseria gonnorrhea following by Staphylococcus aureus. Chronic septic arthritis is rare and reported causative organisms include Mycobacterium tuberculosis and Candida albicans. Bleeding disorders that lead to blood in the synovial fluid typically involve individuals with blood clotting disorders such as hemophilia, von Willenbrand’s disease, Glanzmann’s thrombasthenia, and synovial tumors as well as injuries. Degenerative disorders include primarily osteoarthritis which causes erosion of the joint surfaces and accumulation of fibrin.

The most important reason to perform an analysis on synovial fluid is to rule out septic arthritis. Analysis of synovial fluid is rarely needed in pediatric patients, but is used primarily to differentiate between inflammatory and non-inflammatory disease states. Analysis of synovial fluid usually includes multiple studies such as cell count, microscopic analysis, culture, examination for crystals, and other chemical analysis.

Clinical Utility

  • Diagnosis of joint disease such as gout and traumatic arthritis
  • Differential diagnosis of traumatic arthritis from the immune-based and crystal-induced arthritis
  • As an aid in diagnosis of joint disease due to inflammation and infection
  • Aid in diagnosis of joint injury


Abnormal in:

  • Gout (uric acid)
  • Pseudogout (calcium pyrophosphate deposition disease)
  • Rheumatoid arthritis
  • Infectious arthritis (lactate dehydrogenase)
  • Immune-based arthritis
  • Bacterial infection (protein)
  • Joint injury
  • Lower than normal viscocity is associated with inflammation
  • Decreased clarity (cloudy SF) may indicate crystals, WBCs, or microorganisms in the fluid
  • Reddish SF indicates red blood cells in the fluid which can indicate bleeding disorders
  • Decreased glucose is associated with inflammation but compare with serum glucose

Reference Ranges

  Normal Pathological Normal Pathological
Volume, mL (knee): <4 >4 <0.004 L >0.004 L
String test + (high) - (low)    
Mucin clot Firm Friable    
Clarity Clear Cloudy    
Color Straw Red    
Cell counts        
WBC (u/L) <200 >2000 <0.2 x 10^9/L >2 x 10^9/L
  Percent of total   Fraction of total  
PMN <25 >75   <0.25 >0.75  
RBC <2 >50   <0.02 >0.50  
Total protein (g/dL) 1.2-3.0 >4.0 12-30 g/L >40 g/L
Glucose (mg/dL) Serum level <60   Serum level 3.4 mmol/L




Visual examination, cell count and differential, polarizing microscopic exam for crystals, Gram stain, AFB smear and culture, Culture and susceptibility testing.

Specimen Collection

Synovial fluid aspirate. EDTA (Lavender) preferred, or Heparin (Green) acceptable.

  • Ideally 15 mL divided into two sodium heparin tubes and one sterile tube without additives.
  • Ambient: 48 hours
  • Refrigerated: 48 hours

Additional Testing

Blood/urine uric acid, Blood glucose, Joint bacterial mycobacterial and fungal cultures as indicated, Blood cultures if systemic infection is suspected, ANA, CBC with differential, ESR, C-reactive protein.

Turnaround Time

1-3 days.




E08.610Diabetes mellitus due to underlying condition with diabetic neuropathic arthropathy
E09.610Drug or chemical induced diabetes mellitus with diabetic neuropathic arthropathy
E10.610Type 1 diabetes mellitus with diabetic neuropathic arthropathy
E11.610Type 2 diabetes mellitus with diabetic neuropathic arthropathy
E13.610Other specified diabetes mellitus with diabetic neuropathic arthropathy
G73.7Myopathy in diseases classified elsewhere
H10.8Other conjunctivitis
I00Rheumatic fever without heart involvement
I01Rheumatic fever with heart involvement
I01.0Acute rheumatic pericarditis
I01.1Acute rheumatic endocarditis
I01.2Acute rheumatic myocarditis
I01.8Other acute rheumatic heart disease
I01.9Acute rheumatic heart disease, unspecified
I09.9Rheumatic heart disease, unspecified
I25Chronic ischemic heart disease
I32Pericarditis in diseases classified elsewhere
I39Endocarditis and heart valve disorders in diseases classified elsewhere
I41Myocarditis in diseases classified elsewhere
I51.9Heart disease, unspecified
J99Respiratory disorders in diseases classified elsewhere
M00Pyogenic arthritis
M00.9Pyogenic arthritis, unspecified
M01Direct infections of joint in infectious and parasitic diseases classified elsewhere
M02Postinfective and reactive arthropathies
M02.3Reiter's disease
M02.30Reiter's disease, unspecified site
M02.829Other reactive arthropathies, unspecified elbow
M05Rheumatoid arthritis with rheumatoid factor
M06Other rheumatoid arthritis
M06.9Rheumatoid arthritis, unspecified
M08Juvenile arthritis
M08.0Unspecified juvenile rheumatoid arthritis
M08.1Juvenile ankylosing spondylitis
M08.3Juvenile rheumatoid polyarthritis (seronegative)
M08.80Other juvenile arthritis, unspecified site
M08.90Juvenile arthritis, unspecified, unspecified site
M08.99Juvenile arthritis, unspecified, multiple sites
M10.0Idiopathic gout
M10.00Idiopathic gout, unspecified site
M10.1Lead-induced gout
M10.2Drug-induced gout
M10.4Other secondary gout
M10.9Gout, unspecified
M13Other arthritis
M13.0Polyarthritis, unspecified
M14Arthropathies in other diseases classified elsewhere
M15.0Primary generalized (osteo)arthritis
M15.9Polyosteoarthritis, unspecified
M16Osteoarthritis of hip
M17Osteoarthritis of knee
M18Osteoarthritis of first carpometacarpal joint
M19Other and unspecified osteoarthritis
M19.0Primary osteoarthritis of other joints
M19.90Unspecified osteoarthritis, unspecified site
M19.93Secondary osteoarthritis, unspecified site
M1AChronic gout
M1A.0Idiopathic chronic gout
M25Other joint disorder, not elsewhere classified
M30.3Mucocutaneous lymph node syndrome [Kawasaki]
M45Ankylosing spondylitis
M79.0Rheumatism, unspecified
M86.0Acute hematogenous osteomyelitis
M86.00Acute hematogenous osteomyelitis, unspecified site
M86.1Other acute osteomyelitis
M86.10Other acute osteomyelitis, unspecified site
M86.20Subacute osteomyelitis, unspecified site


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  • Alan Wu. Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders; 4 edition (June 13, 2006). ISBN-10: 0721679757