Causes of Knee Effusions - Differential Diagnosis Framework



Knee Effusion Red Flags:

1. Fever/Chills/Joint pain/Night sweats/Weight loss

	- DDX:

		- Infection

		- Systemic disease

		- Malignancy

2. Non-weight bearing after injury

3. Loss of signal pulses

4. Loss of sensation distal to the knee



Infectious Knee Effusions - Septic Arthritis:

 - Staphylococcal (40%)

 - Streptococcal (28%)

 - Gm - bacilli (19%)

 - Mycobacterium (8%)

 - Gm - cocci (3%)

 - Gram + bacilli (1%)

 - Anaerobes (1%)

 - Watch out for:

	- Gonorrhea

	- Lyme’s disease

	- Syphilis

	- Tuberculosis

	- Brucellosis

	- Viruses: HIV, Chikungunya

	- Herpes virus: CMV, HSV, Varicella, EBV

	- Parvovirus

	- Hepatitis B, C

	- Rubella

	- Alphavirus

	- Fungi: Sporotrichosis, Coccidiomycosis, Candidiasis



Inflammatory Knee Effusions:

 - Gout

 - Pseudo gout

 - Osteoarthritis

 - Overuse syndrome

 - Spondyloarthritis:

 - Reactive arthritis

 - Inflammatory bowel disease

 - Rheumatoid arthritis

 - Juvenile RA/Idiopathic arthritis

 - SLE

 - Behcet Disease



Post-Infectious Knee Effusions:

- Seronegative Reactive Syndrome

- Acute rheumatic fever

- Poststreptococcal reactive arthritis



Traumatic Knee Effusions:

- Ligamentous injuries

- Meniscal injury

- Intra-articulation fracture

- Patellar dislocation



Malignant Knee Effusions:

 - Hematologic

 - Leukemia

 - Ewing’s sarcoma

 - Giant cell tumor

 - Osteosarcoma

 - Eosinophils granuloma

 - Synovial sarcoma

 - Chondroblastoma

 - Benign Tumors:

	- Aneurysmal bone cyst

	- Osteochondroma



Hematologic Knee Effusions:

 - Hemarthrosis

 - Hemophilia

 - Synovium

 - Oral anticoagulant therapy

 - Sickle cell disease



Dr. Ravi Singh @rav7ks



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