We all like to feel like we can heal with our hands.  For this reason, simple reductions are sometimes welcome complaints in your ED that is filled with copious rhinorrhea and voluminous emesis.  We have discussed feeling like Mr. Miyagi during reductions of Nursemaid Elbows.  Another reduction that can make you feel similarly is the Patellar Dislocation, but before you bow as you exit the exam room, make sure that you aren’t being too cavalier.

Patellar Dislocation Basics

• Acute patellar dislocation is a common knee injury.
• Most often occurs in teenagers.

• Most frequently associated with sports or physical activities.
• Often seen when the femur rotates internally, the tibia rotates externally, and the foot is fixed.

Some Important Anatomy

• The Medial Patellofemoral Ligament (MPFL)
  • Thin transverse band that extends from the femur to the medial aspect of the patella.
  • The MPFL is the primary ligamentous restraint for the patella.
    • It provides 50-60% of the restraining force.
  • The MPFL is ruptured in 94-100% of patients with acute patellar dislocation.
  • Repeat dislocation is dependent upon the MPFL injury rather than other predisposing factors (some listed below):
    • Lateral patellar tilt
    • Patella alta (abnormally high patella)
    • Trochlear dysplasia
    • Increased Q angle
    • Genu Valgum
    • Vastus Medialis Muscle hypoplasia
    • Increased femoral anteversion
    • Congenital conditions that lead to ligament laxity

Reduction of Patellar Dislocation

• Be Kind! Give some Pain Meds!! Nitrous Oxide would be nice also!

1. Flex the Hip to relax the Quads.
2. Apply medial pressure to the lateral edge of the dislocated patella.
3. While continuing to apply medial pressure, extend the knee.

• See friend and colleague, Dr. Larry Mellick’s Video.

Imaging

• Most typical patellar dislocations can be reduced without initial radiologic imaging.

• Xrays will be needed, however, to help assess patellar location and assess for fractures afterwards.
• MRI is also helpful in evaluating the MPFL (actually better than arthroscopy).
  • Naturally, this can occur as an outpatient through the Orthopaedic office.

What’s Next?

After you have done the Mr Miyagi part and feel like a superhero following the reduction, the patient/family will likely have some more questions.

• It’s a good idea to keep the patient in a knee immobilizer until Ortho follow-up.
• Discuss the potential for MRI based on the Orthopod’s preference.

• Traditionally, conservative / non-operative management has been advocated for after 1st dislocation; however, there is a growing trend favoring reconstruction of the MPFL to help avoid a second dislocation.
  • This will be depend upon whether there are boney abnormalities (fractures, other anatomic anomalies) and the Orthopod’s preference.
  • It is a good idea to know that not all are treated conservatively anymore… just so you don’t misguide the family inadvertently.

References