Epidemiology: A patella subluxation of dislocation can occur at any age. Some athletes may have “miserable malalignment syndrome” (external tibial torsion / pronated feet, genu valgum, and femoral anteversion) which predisposes them to having a subluxation or dislocation episode. Athletes who have patella alta (high riding patella), decreased VMO muscle bulk, and tight lateral structures are also predisposed to have a subluxation or dislocation episode.
Mechanism of Injury/Description: A patella subluxation or dislocation occurs when the patella (knee cap) comes out of the patellofemoral groove. Subluxation refers to the knee cap partially moving out of place while a dislocation means it has completely moved out of place. This can occur from a direct hit to the patella (knee cap) or from a noncontact extended (straight leg) plant and twisting motion.
Signs/Symptoms: Signs/symptoms of a patella subluxation or dislocation include experiencing acute/sudden pain, deformity, inflammation (swelling), feelings of instability or that the knee has “popped out.”
Diagnosis: The diagnosis of a patella subluxation or dislocation is determined by performing a physical exam which shows a positive apprehension test, inflammation (swelling) of the knee, tenderness to palpate on the MPFL, and a positive J sign. An x-ray will show a lateral patellar tilt (subluxation) or dislocation of patella (dislocation) from the patellofemoral groove. An MRI is also recommended to be ordered to evaluate for ligamentous, cartilage, loose bodies, and other injury to the knee.
Treatment: The treatment for a subluxation episode is rest from impact/pounding/landing, wearing a patellar stabilizing brace, and to work with physical therapy. For a dislocation, seek emergency treatment to have your knee (patella) put back into place and then once relocated a brace, and physical therapy are the main treatments but sometimes surgical intervention may be needed to stabilize your patella.
Prevention: To prevent this injury focus on VMO strength, stretching hip flexors and ITB, practice proper landing mechanics, and avoid valgus/knocked knees when landing.
Gymnastics Medical Provider PEARLS: If you are a medical provider the technique to relocate a dislocated patella is to straighten the knee and then use a knee immobilizer and transport to the local hospital/emergency department. Never perform any medical tests/treatments unless you are legally allowed to.
Gymnast, Parent, and Coach PEARLS: Gymnasts who continue to have subluxation episodes and have failed conservative treatment (rest, bracing, and PT) may require surgical stabilization. Talk with a pediatric sports medicine surgeon who reviews your options.