CanadiEM Frontline Primer

CanadiEM Frontline Primer – MSK – Joint Pain

In Medical Concepts by Afsheen MeharLeave a Comment

Can’t Miss Diagnoses

  • Septic Arthritis
  • Trauma
  • Also, assess overlying soft tissues for infections which can also be very life-threatening (e.g. Necrotizing Fasciitis).
  • Open Joint
  • Prosthetic Joint Infection
  • Gout
  • Rheumatoid arthritis
  • Osteoarthritis
  • Hemarthrosis
  • Dislocations

DDx for Monoarticular Arthritis

O – Osteoarthritis
S – Septic arthritis
T – Tumor in nearby bone / Trauma
R – Rheumatic & autoimmune disease
I – Intra-articular pathology
C – Crystal arthropathy (Gout, pseudogout)
H – Hemarthrosis

More details here!

DDx for Prosthetic Joint Pain:
  • DDX for Prosthetic Joint Pain:
  • Septic Loosening
  • Aseptic Loosening
  • Fracture
  • Dislocated/damaged polyethylene liner (especially in Unicompartmental Knee Replacements)

Points to focus upon

To note and document; Tetanus status, anticoagulation, surgical manipulation if any

If Joint Pain & Fever, must suspect septic joint, especially if a patient has no history of similar pain OR has any of the following risk factors:
– recent intravenous drug use
– Diabetes Mellitus
– immunocompromise
– elderly

Check for White count, CRP, Joint aspiration

Polyarticular arthritis is usually suggestive of a more systemic problem. Consider a sexual history in these patients or in any young patients with joint pain. Before you go hog-wild on tests, chat with your rheumatology colleague and/or consult this resource.

Prosthetic Joints- all joints should be aspirated with sterile technique. However, this is especially applicable to prosthetic joints. If there is an orthopaedic doctor on call, it is worth discussing with them prior to doing an aspiration. If an aspiration of a prosthetic joint is going to be done, a full drape, sterile setup, and sterile technique must be followed. When calling the orthopaedic surgeon, ideally know the date of original surgery, surgeon, and onset of symptoms. This most applicable for knees. Hips should be done under image guidance.

Clinical Decision Tools


  • CBC, BUN, Cr, Lytes, Glucose, VBG,
  • C-reactive protein (CRP), ESR (if available at your lab)
  • Consider joint aspiration
  • Consider weight-bearing X-rays for lower extremity.
  • REMEMBER: All x-rays need 2 at least 2 views, for knee joint pain include a sunrise or patellar view.


Septic arthritis will require surgical wash-out. Involve your consultants early if this is a suspicion. Also, don’t be a hero if you are not confident with your aspiration technique. Remember, during COVID-19 many hospitals have shut down their operating rooms and your orthopedics colleagues may be available to help – especially if you are redeployed to the ED. NEVER ASPIRATE THROUGH A CELLULITIS, FIND CLEAN TISSUE AND AVOID MAJOR VESSELS/NERVES.

Joint aspiration – Medscape Article
First 10:EM – Joint Aspiration Video

Recommended reading, videos, and podcasts

Would you like to read more MSK topics? Read about common fractures, or extremity soft tissue pathologies.

This is part of the CanadiEM Frontline Primer. An introduction to the primer can be found here. To return to the Primer content overview click here.

This post was copyedited and uploaded by Evan Formosa.

Afsheen Mehar

Dr. Afsheen Mehar is a resident physician at the University of Toronto in the RCPSC Emergency Medicine Training Program. Her greatest passions are medical education, POCUS and austere medicine. She holds an RDMS certification in ultrasound.

Teresa Chan

Senior Editor at CanadiEM
Emergency Physician. Medical Educator. #FOAMed Supporter, Producer and Researcher. Chief Strategy Officer of CanadiEM. Associate Professor, Division of Emergency Medicine, Department of Medicine, McMaster University.

Colm McCarthy

Colm completed his residency at McMaster University in orthopaedic surgery along with a 5 month fellowship in orthopaedic trauma surgery. He will be having a second fellowship in hip and knee reconstruction at the Brigham and Women’s Hospital. He enjoys collaborative work, medical education, and physical advocacy.