John P. Fulkerson, MD, Robert F. LaPrade, MD, Ph.D., Vicente Sanchis-Alfonso, MD, Seth L. Sherman, MD, and Beth E. Shubin Stein, MD.


A common injury seen in orthopedic surgery, patellar dislocation accounts for about 2% to 3% of knee injuries and is the second most traumatic knee injury after ACL tears in the adolescent and young adult population.

“If somebody has a twisting injury of their knee, the first most likely diagnosis is an ACL [tear],” Beth E. Shubin Stein, MD, sports medicine surgeon and co-director of the Women’s Sports Medicine Center at Hospital for Special Surgery, told Healio/Orthopedics Today. “The second most common diagnosis is patellar dislocation and that is in the second and third decades of life, which is the teens and 20s.”

Whether an adolescent athlete experiences an ACL tear or a patellar dislocation depends on the patient’s anatomy, according to Shubin Stein. She said the most common reason for a patellar dislocation lies in the shape of the patient’s trochlea.

“When [the trochlear] groove or track is not shaped correctly, it can be shallow or it can even be flat, then that person is more likely to sustain a patellar dislocation because the groove is not shaped well,” Shubin Stein, an Orthopedics Today Editorial Board Member, said.

In addition, Shubin Stein said patients with ligamentous laxity, an abnormally high patella or patella alta, or a significantly elevated tibial tubercle-trochlear groove distance can also be at risk for patellar dislocation.

“A lot of the teenaged girls who do have patellar dislocations do not necessarily have the best overall strength, which puts them at a higher risk to having an ipsilateral patellar dislocation,” LaPrade said.

For the complete study: Best treatment unknown for primary patellar dislocation

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