Anterior View of the Knee (www.howardluksmd.com)

Definition: Stretch or tear of the medial collateral ligament (MCL).

Epidemiology

  • Ligamentous injuries have been cited to account for ~40% of knee injuries (Bolen 2000)
  • The MCL is the most commonly injured ligament, accounting for ~8% of all knee injuries (Majewski 2006)
  • Women > Men (Swenson 2013)

Mechanism

  • Direct blows are the most common mechanism and typically cause more severe injuries (Singhal 2010).
  • Indirect mechanisms are less common. They occur with a valgus stress with external rotation force to the lateral knee, i.e. when an athlete’s shoe gets caught on a playing surface during quick direction changes, or when an athlete catches a tip or the inside edge of a ski or skate.
  • The MCL is the first (and therefore most common) structure affected in a predictable series of injuries from a valgus stress

Order of Ligamentous Disruption (Simon’s Orthopedics)

Physical Exam

  • General Principles
    • Should be performed as soon as possible as swelling and muscle spasm occur early and obscure assessment
    • Both knees should be examined using a systematic approach – inspection, palpation, testing range of motion, and using special maneuvers specific for certain injury patterns
    • While it is important to evaluate the entire knee, this section will focus on findings specific to MCL injuries
  • Inspection
    • Assess the patient’s gait and ability to bear weight which can sometimes indicate injury severity
    • Patients can often have localized swelling but effusions are uncommon in isolated MCL injuries.
    • The presence of an effusion is highly suggestive of associated fractures, meniscal or cruciate injuries.
  • Palpation
    • Tenderness at the medial joint line suggests MCL injury
    • Can also indicate medial meniscal injury and is therefore a nonspecific finding
  • Range of Motion
    • Pain from an isolated MCL injury can limit active motion, particularly terminal knee extension and flexion beyond 100 degrees
    • Isolated MCL injury generally does not constrain passive range of motion
  • Special Maneuvers – Valgus stress (abduction) test
    • Laxity at 30 degree flexion => MCL injury
    • Laxity at full extension => MCL +/- ACL/PCL injuries.
    • To objectively assess laxity, hold finger at medial joint line and feel for medial joint widening (see injury grading below).
    • Ultrasound can help quantify degree of medial joint widening.
    • Always compare to uninjured knee to understand baseline joint laxity     
    • Detection of ligamentous laxity can be limited by spasm of surrounding muscles

Injury Classification

  • Grade I (mild)
    • Stretch injury
    • No laxity elicited with valgus stress (i.e. <5mm medial joint widening)
  • Grade II (moderate)
    • Partial tear of MCL
    • 5-9mm medial joint widening
  • Grade III (severe)
    • Complete tear
    • 10mm or more of medial joint widening
    • Typically less painful versus lower grade injuries

MCL Injury Grading System (zamst.us)

ED Management

  • Regardless of injury grade, ED management of isolated MCL injuries is supportive
    • Ice, compression, elevation, and NSAIDs
    • Weight bearing as tolerated
    • A hinged knee brace should be applied
      • Protect against additional valgus injury
      • Avoid knee immobilizers as they can lead to knee stiffness and muscle weakness
    • Always encourage early mobilization (within the first week)
  • Indications for emergent ortho consultation
    • Associated open fracture
    • Neurovascular deficit
    • Suspected tibiofemoral dislocation
    • Unstable knee joint
      • Due to muscle spasm and soft tissue swelling, an unstable knee might appear stable
      • Immobilize, make non-weight bearing, and obtain close follow-up if unstable joint without evidence of dislocation (within 1 week) for re-examination

Reverse Second Fracture: Case courtesy of Dr Maulik S Patel, Radiopaedia.org. From the case rID: 19490

Imaging in the ED

  • Plain Radiographs
    • Views: AP, lateral, patellar (45 degrees flexion)
    • Generally not necessary to evaluate isolated MCL injuries, but should be performed if concern for associated fractures
    • Typically normal in isolated MCL injuries
    • A “reverse segond” fracture is a subtle avulsion fracture of the medial tibial condyle that represents an avulsion of the deep portion of the MCL 
  • Ultrasound (Craft 2015)
    • Can identify MCL injuries via abnormal MCL appearance
    • Can quantify degree of medial joint opening during valgus stress testing
  • CTA: Should be performed in all patients with clinical features concerning for an unstable knee, who do not have hard signs of vascular injury
  • MRI: Can be done at outpatient for simple MCL injury to help identify extent of injury.

Prognosis

  • Functional recovery from isolated MCL injuries is dependent on grade of injury, and achieved with physical therapy focused on gradual strengthening and range of motion exercises
    • Grade I: return to activity in ~1wk
    • Grade II: 2-4wks
    • Grade III: 4-8wks
  • Multiple prospective case-control studies have shown no difference in functional outcomes for non-op vs operative management in isolated MCL injuries (Reider 1994, Lundberg 1996, Lundberg 1997).

Take Home Points

  • MCL injuries are commonly seen in the ED and the diagnosis is based on the physical exam
  • Isolated MCL injuries can be managed conservatively in the ED, and safely discharged with sports medicine follow-up in 1-2 weeks
  • If the patient has an unstable knee or an effusion, consider a tibiofemoral dislocation

Read More

Core EM: True Knee and Patellar Dislocations

References

McMahon PJ et al. Chapter 3. Sports Medicine. Current Diagnosis & Treatment in Orthopedics, 5e Eds. Harry B. Skinner, and Patrick J. McMahon. New York, NY: McGraw-Hill, 2014

Bond MC. Chapter: Knee. Simon’s Emergency Orthopedics, 7e Ed. Scott C. Sherman. New York, NY: McGraw-Hill, 2014

Bollen S et al.  Epidemiology of knee injuries: diagnosis and triage. Br J Sports Med. 2000;34(3):227-8. PMID: 10854030

Majewski M et al. Epidemiology of athletic knee injuries: A 10-year study. Knee. 2006; 13(3): 184-8. PMID: 16603363

Swenson DM et al. Epidemiology of knee injuries among U.S. high school athletes. Med Sci Sports Exerc. 2013 Mar;45(3):462-9. PMID: 23059869

Singhal M et al. Medial ligament injuries. In: DeLee and Drez Orthopaedic Sports Medicine, DeLee J, Drez D, Miller M (Eds), Saunders, Philadelphia 2010. p.1629.

Kaufman SL, Martin LG. Arterial injuries associated with complete dislocation of the knee. Radiology 1992; 184(1):153-5. PMID:1609074

Craft JA, Kurzweil PR. Physical examination and imaging of medial collateral ligament and posteromedial corner of the knee. Sports Med Arthrosc. 2015; 23(2):e1-6. PMID: 25932881

Lundberg M, Messner K. Long-term prognosis of isolated partial medial collateral ligament ruptures. A ten-year clinical and radiographic evaluation of a prospectively observed group of patients. Am J Sports Med. 1996; 24(2): 160-3. PMID: 8775113

Reider B et al. Treatment of isolated medial collateral ligament injuries in athletes with early functional rehabilitation. A five-year follow-up study. Am J Sports Med. 1994; 22(4): 470-7. PMID: 7943511

Lundberg M, Messner K. Ten-year prognosis of isolated and combined medial collateral ligament ruptures. A matched comparison in 40 patients using clinical and radiographic evaluations. Am J Sports Med. 1997; 25(1): 2-6. PMID: 9006684