Effects of lateral retinacular release on the lateral stability of the patella

The objective of this cadaveric study was to evaluate quantitatively the effects of lateral retinacular release on the lateral stability of the patella. A materials testing machine was used to displace the patella of seven cadaveric specimens 10 mm laterally while measuring the required force, with 175 N quadriceps tension. The patella was connected via a ball-bearing patellar mounting 10 mm deep to the anterior surface to allow rotations. Patellar force--displacement behaviour was tested from 0 degrees to 60 degrees knee flexion. At 0 degrees, 10 degrees and 20 degrees flexion the mean force required to displace the patella 10 mm laterally was reduced significantly due to lateral retinacular release, by 16-19%. The average force required to displace the patella was also reduced for larger flexion angles, although this was not statistically significant. These findings suggest that lateral retinacular release may not be appropriate in treatment of patellar lateral instability.