1. No category

Approach to Acute Monoarthritis
of the Knee
Henry Averns
Assistant Professor Rheumatology Division
Queens University
Aims of Workshop
• To consider the differential diagnosis of acute
and chronic knee monoarthritis
– I.e. provide a systematic approach to the
investigation and differential diagnosis of patients
presenting with monoarticular pain.
• To briefly review examination of the knee
• To discuss indications for aspiration and
injection of the knee
• To practice knee injection on model knees
APPROACH TO MONOARTHRITIS OF THE KNEE
MONOARTHRITIS
POLYARTHRITIS
Acute or Chronic?
Is it inflammatory?
Extra- articular features?
ARTICULAR
EXTRAARTICULAR
Systemic or local problem?
History I
• Age, time profile
• Features of inflammation
– stiffness, redness, pain, swelling, warmth
• Preceding illness
– GU or GI infection
– history of trauma, portal of entry for infection
• Associated symptoms
– red eye, rash, balanitis
History 2
• Associated medical complaints
– psoriasis, IBD, Ankylosing spondylitis
– bleeding disorders
– predisposition to infection
• Drug history
– immunosuppressants, aspirin, diuretics
• Family history
– of gout, psoriasis, IBD, AS
Differential diagnosis I
• Acute monoarthritis
– Septic arthritis (staph aureus)
– Reactive arthritis
• GI infection - campylobacter, salmonella, shigella, yersinia
• GU infection - chlamydia
– Crystal arthritis
• Gout (uric acid)
• Pseudogout/chondrocalcinosis/calcium pyrophosphate
deposition disease (CPPD)
• Haemarthrosis
Septic Arthritis
Risk factors
• prosthetic hip or knee joint,
• skin infection,
• joint surgery,
• rheumatoid arthritis,
• age greater than 80 years,
• diabetes mellitus.
•Intravenous drug use and large-vein catheterization
are predisposing factors for sepsis in unusual joints
(e.g., sternoclavicular joint).
Common Errors in Diagnosing Acute Monoarthritis
The problem is in the joint, because the patient The soft tissues around the joint can be the
complains of "joint pain."
source of the pain (e.g., prepatellar bursitis of
the knee).
Crystal-proven diagnosis of gout or pseudogout Crystals can be present in a septic joint.
rules out infection.
The presence of fever is useful in distinguishing Fever may be absent in patients with
infectious causes from other causes.
infectious monoarthritis but can be a
presenting feature in acute attacks of gout or
pseudogout.
A normal serum uric acid level makes gout a less Serum uric acid levels often are lowered in
likely diagnosis.
patients with acute gout (30%). There may be
unrelated hyperuricemia in patients with other
conditions.
Gram staining and culture of synovial fluid are Culture results may be negative in early
sufficient to exclude infection.
infection
Examination of the Knee
• Demonstration
• Module
ARTHROCENTESIS / INJECTION
• Indications
– Diagnostic
• Synovial fluid analysis
– Therapeutic
• Inflammatory arthritis
• Gout
• Osteoarthritis
ARTHROCENTESIS
The things you need;
ARTHROCENTESIS
• Contraindications
– Infection locally OR elsewhere
– Abnormal skin (relative CI)
– Warfarin therapy is not a contraindication
• No touch technique adequate
• Local anaesthesia difficult to achieve…is it
worth it? Probably not
• Have appropriate tubes ready
Additional slides for reference
Extra-articular features which suggest
seronegative spondyloarthritis
– nails (pitting, ridging, hyperkeratosis)
– enthesitis, dactylitis and tenosynovitis
– nodules (elbows/ears)
– skin (local infection, psoriasis, keratoderma
blenorrhagicum, balanitis)
– eyes (conjunctivitis, uveitis)
– mouth ulcers
Investigations I
•
•
•
•
Haematology - CBC, ESR, clotting
Biochemistry - U&E, LFTs, urate, CRP
Immunology
Microbiology
– blood/urine/stool/urethral/sputum cultures
– serology
Investigations II
• Synovial fluid
– volume/viscosity/cellularity
– polarised light microscopy (crystals)
– gram stain/culture
• Imaging
– plain films
• loss of joint space, osteophytes, subchondral cysts,
osteosclerosis, erosions, chondrocalcinosis
– MRI, bone scan
Septic Arthritis
1.
2.
3.
4.
Staph aureus—most common
Strep (splenic dysfunction)
Neisseria gonorrhea (young, sexually active)
Gram negatives (immunocompromised, GI
infection)
5. Mycobacteria (immunocompromised)
6. Fungus (immunocompromised)
7. Lyme disease
Acute septic
arthritis
Staph aureus
+++
Coag neg staph
Prosthetic joint
infection
+++
Acute
osteomyelitis
+++
+++
Chronic
osteomyelitis
+++
+
Haemolytic
strep
++
++
++
Skin anaerobes
+
+++
+
Gram negative
cocci
+
H influenzae
+
++
+
+
Ps aeruginosa
+
+
+
+
Salmonella
+
+
+
+
Intestinal
anaerobes
Mycobacteria
+
+
+
+
+
+
+