The moving patellar apprehension test for lateral patellar instability

Abstract

Background: Physical examination maneuvers for patellar instability are often inaccurate.

Hypothesis: The "moving patellar apprehension test" is a sensitive and specific physical examination technique for the diagnosis of patellar instability.

Study design: Cohort study (diagnosis); Level of evidence, 3.

Methods: The moving patellar apprehension test was performed in an office setting preoperatively and compared with the ability to dislocate the patella when examined under anesthesia in 51 patients. The examination begins with the knee held in full extension and the patella is manually translated laterally with the thumb. The knee is then flexed to 90 degrees and then brought back to full extension while the lateral force on the patella is maintained. For the second half of the test, the knee is started in full extension, brought to 90 degrees of flexion, and then back to full extension while the index finger is used to translate the patella medially. For a positive test in part 1, the patient orally expresses apprehension and may activate his or her quadriceps in response to apprehension. In part 2, the patient experiences no apprehension and allows free flexion and extension of the knee.

Results: When compared with the ability to dislocate the patella under anesthesia, the moving patellar apprehension test was found to have a sensitivity of 100%, a specificity of 88.4%, a positive predictive value of 89.2%, a negative predictive value of 100%, and an accuracy of 94.1%.

Conclusion: The moving patellar apprehension test is an accurate physical examination technique that, when performed and interpreted correctly, is highly sensitive and specific for patellar instability.