Le Genou: Everything you Knee-d to know!

The acutely injured knee can often be challenging to assess when there is no associated fracture. Identifying the possible non-bony acute pathology is important to help discern the most appropriate approach to treatment for the patient.

Assessment

History

Mechanism of action
- - Contact
  - Twist/Pivot
Onset of symptoms:
- - Immediate vs delayed symptoms
  - Able to finish their activity?
Symptoms
- - Where the pain is felt
  - Mechanical symptoms; catching, clicking, locking
  - Giving out/unstable
Past Medical History for Risk Factors:
- - Medications (steroids, fluroquinolones), diabetes, connective tissue disease
  - What is their baseline function? i.e.: young athlete vs injury during bed to wheelchair transfer

Exam

Position:
- - Supine
  - Bilateral leg exposure
  - Most comfortable position for patients
  - Support leg as much as possible throughout exam (provide towel under knee for comfort)
  - Limit movement
Observe:
- Can they ambulate?
Analgesia:
- - Prior to exam
  - +/- Procedural sedation for patella reduction
PoCUS:
- - Helpful to identify fractures, tendon injury, effusions
Arthrocentesis:
- - Should be considered in patients with acute knee injury with a large effusion, decreased ROM and normal X-Ray
  - Arthrocentesis performed in the ED for ACL injury causing effusion, pain and decreased ROM showed improvement in pain, range of motion and accuracy of exam maneuvers at follow-up visit (Wang et al. 2016).
Traumatic Hemarthrosis (Potpally et al 2021)
- - 70% of ACL tears
  - 10% of patella subluxation/dislocation
  - 10% of meniscal tears
  - 5% of osteochondral fractures
  - 5% other (i.e.: PCL tears)
Movements to check:
- - Check Extensor mechanism while supine, not sitting as ITB is a knee extensor at 30 degrees of knee flexion when it moves from posterior to anterior over the lateral femoral condyle
  - Stability (ligaments)
  - Intra-articular (meniscal)

Ottawa Knee Rules

Patients presenting with acute knee injury require X-ray if:

Pathologies

Occult Knee Dislocation

Mechanism of injury:
- - Dashboard/MVC
  - Ground level falls in elderly or obese patients
  - 20-50% of knee dislocations will spontaneously reduce prior to ED arrival
Exam:
- - Ligamentous instability in at least 3 of the 4 ligatments
ED investigations:
- - X-Ray to rollout fracture
  - Ankle-Brachial index
  - CT-A
ED Management:
- - If hard signs of vascular injury; STAT vascular consult +/- vascular injury
  - If abnormal ABI –> CT-A (consult ortho +/- vascular)
  - If normal ABI –> consult ortho
Referral:
- - Consultation in the ED for admission/management

Patella Dislocation

Mechanism of Injury:
- - Planted foot with internal rotation/twisting on a valgus flexed knee
  - Dancing, baseball swing, quick lateral change
  - Lateral dislocation most common
Exam:
- - Laterally displaced patella for lateral dislocation
  - Subluxation: positive patella apprehension test
Investigations:
- - X-Ray with skyline views to rollout acute fracture (osteochondral fractures commonly missed)
  - X-Ray not required prior to reduction (Krause et al, 2013)
ED Management
- - Reduce by straightening leg and gently tip & tilt patellar laterally then medially
  - Immobilize
  - Counsel
    - - Brief immobilization for comfort (3-4 days)
      - Ice and elevate
      - Weight bearing as tolerated
      - Limit walking, standing, repetitive bending
      - Use a patella restraining brace
      - Physiotherapy for retraining/strengthening quads
      - Athletes return to play in 4-6 weeks
- Referral:
  - - Plater clinic if: associated fracture, recurrent dislocations, associated injury (eg: ACL, MCL tears)
    - All reduced dislocations can be referred to plaster clinic/orthopedics, or if there are absolutely no concerns for other injuries they can be sent to their family physician or sports medicine specialist.
    - Physiotherapy

Patella Tendon Rupture

Mechanism of injury:
- - Jumping sports
  - Sudden quadriceps contraction with flexed knee (patellar tendon injury)
  - Sudden quadriceps contraction when landing from a jump with a flexed knee (Quads tendon injury)
Exam:
- - Extensor mechanism will not be intact, therefore unable to complete straight leg raise
  - Defect distal to the patella (defect proximal to patella suggests quads tendon rupture)
ED Investigations:
- - X-Ray to rule out fracture – patella alta (patella tendon rupture), patella baja (quad tendon rupture)
  - PoCUS: identify the tendon defect

Patelle Baja

ED Management:
- - Immobilize in zimmer
  - Consult ortho in ED to book for surgery
Referral:
- - Surgical intervention required

Ligamentous Injury

Anterior Cruciate Ligament:

Mechanism of injury:
- - Non contact: pivot
  - Contact: blow to lateral aspect of knee
Exam:
- - Lachman
  - Anterior Drawer
  - Lever Sign
  - Pivot Shift Test – not accurate in the ED
ED Investigations:
- - X-Ray to look for Segond or tibial spine fracture
ED Management:
- - Crutches, WBAT, RICE
Referral:
- - In young athletes that you are confident have an ACL tear -> outpatient MRI + ortho referral
  - If you are not confident that there is a significant injury, they need to be re-examined in ~1wk -> family physician or sports medicine referral
  - Minor injury or poor baseline -> family physician

Medial Collateral Ligament

Mechanism of injury:
- - Contact: blow to lateral aspect of knee
Exam:
- - Laxity/soft end feel with valgus stress test at 30 degrees of knee flexion for isolated MCL injury
ED Investigations:
- - X-Ray to rule out fracture
ED Management:
- - Crutches, WBAT, RICE
Referral:
- - In young athletes that you are confident have at least a MCL tear -> outpatient MRI + ortho referral
  - If you are not confident that there is a significant injury, they need to be re-examined in ~1wk -> family doctor or sports medicine referral

Lateral Collateral Ligament

Mechanism of injury:
- - Contact: blow to medial aspect of knee
Exam:
- - Laxity/soft end feel with varus stress test at 30 degrees of knee flexion for isolated LCL injury
ED Investigations:
- - X-Ray to rule out fracture
ED Management:
- - Crutches, WBAT, RICE
Referral:
- - Family physician or sports medicine specialist for re-examination +/- imaging
  - Isolated LCL injuries are rare

Posterior Cruciate Ligament

Mechanism of injury:
- - Dashboard
  - Hyperflexion with plantar flexion of foot
Exam:
- - Posterior Sag Sign
  - Posterior Drawer
  - Could have valgus/varus laxity at 0 degrees of knee flexion
  - Dial test to differentiate isolated PCL vs associated injuries (PLC)
  - ED Investigations:
    - - X-Ray to rule out fracture
  - ED Management:
    - - Crutches, WBAT, RICE
  - Referral:
    - - Family physician or sports medicine specialist for re-examination +/- imaging.
      - In young athletes that you are confident have at least a high grade PCL tear -> outpatient MRI + ortho referral

Posterolateral Corner

Mechanism of injury:
- - Non contact: external rotatory/twisting
  - Contact: blow to anteromedial aspect, hyperextension, MVC (knee dislocation)
Exam:
- - Varus and Valgus stress at 0 degrees of knee flexion
  - Dial test
  - Reverse pivot shift test (not accurate in the ED)
ED Investigations:
- - X-Ray to rule out fracture
ED Management:
- - Unstable knee (at least 3 ligaments torn) -> ortho in the ED
  - Crutches, WBAT, RICE
Referral:
- - Sports medicine specialist or family physician for re-examination +/- imaging

Meniscus

Mechanism of injury:
- - Non contact: sudden change in direction – commonly seen in soccer, basketball, football and rugby
Exam:
- - Joint line tenderness
  - McMurray
  - Thesslay
  - Apley
- ED Investigations:
  - - X-Ray to rule out fracture
- ED Management:
  - - Crutches, WBAT, RICE
- Referral:
  - - If mechanical symptoms (locking) -> Outpatient MRI + ortho referral
    - If no mechanical symptoms -> family physician or sports medicine specialist for re-examination +/- imaging

References

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Chahla, J., Moatshe, G., Dean, C. S., & Laprade, R. F. (2016). Posterolateral Corner of the Knee: Current Concepts. The Archives of Bone and Joint Surgery, 97(9), 97–103.

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Author

Julie Ingratta

Dr. Ingratta (she/her) is a senior Emergency Medicine Resident at the University of Ottawa.

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