What is Trochlear Dysplasia?

Trochlear dysplasia is a congenital condition of the knee characterized by an abnormal shape of the trochlear groove—the depression at the lower end of the femur that accommodates the kneecap (patella). In this condition, the groove, particularly at its upper end, may appear unusually flat or even elevated into a ‘bump,’ disrupting normal knee mechanics.

What Causes Trochlear Dysplasia?

Trochlear dysplasia is primarily a condition one is born with. It results from abnormal development and is rarely attributed to trauma or injury, such as damage to the patella during early childhood. As research indicates:
“The shape of the trochlea is largely maintained during growth and development and does not change significantly after birth.”
— Onor GI Jr, Yalcin S, Kaar SG, et al. (2021)

Trochlear Dysplasia and Patellar Instability

This condition is a leading factor in recurrent patellar instability. The abnormal trochlear shape fails to provide adequate containment for the kneecap, leading to episodes of subluxation (partial dislocation) or full dislocation. Severe cases often exhibit a noticeable lateral slipping of the patella during near-full extension of the knee—a clinical sign referred to as the ‘J-sign.’

As noted in the literature:
“Trochlear dysplasia has been proposed to be one of the most significant factors implicated in recurrent patellar instability.”
— Onor GI Jr, Yalcin S, Kaar SG, et al. (2021)

Management and Treatment

Patients with symptomatic trochlear dysplasia may benefit from tailored interventions, including physiotherapy to strengthen supporting muscles or surgical procedures to realign and stabilize the patella. Early consultation with an orthopaedic specialist is crucial for personalized care and improved outcomes.

For further information or to schedule an evaluation, contact our clinic today.