Patellar Apprehension Test

Context

The Patellar Apprehension Test (PAT) is commonly used to aid in the diagnosis of patellar instability.

Patellar instability can result from a traumatic event combined with predisposing anatomical factors, which increase the risk of dislocation. An accurate diagnosis is necessary to initiate appropriate treatment.

Video of the Test

Execution

To perform the test, according to Ahmad et al. (2009), the patella is moved laterally while the patient lies on their back. The knee is then flexed to 90° and returned to extension. For the second part, the knee is flexed to 90°, then fully extended while the patella is moved medially. For the test to be considered positive, apprehension must occur during the first part but not during the second part.

Note that this is a modified version of the test. The original version involves only firm pressure applied to the medial edge of the patella in a fully extended and relaxed knee.

Clinical Value

In the study by Ahmad et al. (2009), the test was performed preoperatively and during a knee examination under anesthesia in 51 patients. The test performed during examination under anesthesia was considered the gold standard for diagnosing patellar instability. For the detection of patellar instability, the preoperative test had an accuracy of 94.1%, a sensitivity of 100%, a specificity of 88.4%, a negative predictive value of 100%, and a positive predictive value of 89.2%.

Since then, other studies have evaluated the original version of this apprehension test, and in 2023, Lastoria and colleagues conducted a systematic review of the test’s validity in the context of patellar instability.

The authors note that, based on current evidence, the Patellar Apprehension Test has high sensitivity and specificity. The intra- and inter-rater reliability of the PAT varies widely due to its subjective nature. Given this, although the PAT can be used to provide a provisional diagnosis of patellar instability, it cannot be used alone to confirm the diagnosis of recurrent patellar instability.

To do so, several tests and investigations are necessary, including a functional assessment using validated scoring tools and imaging. The authors suggest that further research should explore the association between a positive PAT and anatomical parameters in imaging. Additionally, studies comparing the accuracy of the PAT and radiological examinations should be conducted.

The reliability of the conclusions drawn by the authors of this systematic review is limited by the shortcomings of the current evidence. These include the lack of a standardized approach to performing the PAT, the failure to report surgical outcomes based on whether the test result was positive, and the lack of a comparison of the PAT’s validity before and after surgery.