AANA/SOMOS Course Materials (August 2021)-Patella Instability in the Special Operator

Patella Instability in the Special Operator

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This presentation by Dr. Robert Burks focuses on patella instability, particularly in the context of special operators or highly active individuals. Patella dislocation generally occurs not solely due to malalignment but primarily when passive stabilizers, especially the medial patellofemoral ligament (MPFL), are damaged. Anatomically, stabilizers include the medial patellofemoral ligament (MPFL), medial patellotibial ligament (MPTL), vastus medialis oblique (VMO), and medial collateral ligament (MCL).<br /><br />Basic scientific cadaveric studies show the MPFL contributes about 53-60% of the restraining force preventing lateral patellar dislocation. Thus, treatment often targets reconstructing the MPFL, analogous to ACL reconstruction for ACL injuries. However, evaluation of patella instability requires assessing four main factors: malalignment, valgus deformity, patella alta (high-riding patella), and trochlear dysplasia (abnormal groove shape).<br /><br />Key measurements include the tibial tubercle–trochlear groove (TT-TG) distance, with abnormal values over 20 mm indicating increased instability risk; patellar tendon overlap ratio (PT-LTR), and patellar tilt angles. Patella alta is defined using ratios on imaging (e.g., Caton-Deschamps, Blackburn-Peel indices), with about 25% of patients showing alta based on MRI measurements.<br /><br />Trochlear dysplasia is characterized by abnormal trochlea shape or bump, which contributes to instability.<br /><br />Dr. Burks emphasizes that successful MPFL reconstruction relies on proper graft placement with minimal tension to avoid complications such as overconstraint, decreased motion, cartilage overload, or patella fracture. Rehabilitation is structured from early range of motion and protected weightbearing to gradual quadriceps strengthening and return to sport by 3-6 months.<br /><br />A clinical case of a 23-year-old athlete with patella instability and TT-TG of 18.6 mm underwent MPFL reconstruction, with good functional recovery at 3 months, no limitations, and 90/100 subjective score.<br /><br />In summary, patella instability treatment focuses on restoring MPFL function while addressing alignment and anatomical risk factors for optimal outcomes in active individuals.

Keywords

patella instability

medial patellofemoral ligament

MPFL reconstruction

tibial tubercle–trochlear groove distance

patella alta

trochlear dysplasia

valgus deformity

patellar dislocation

medial patellotibial ligament

vastus medialis oblique