Jerk Test

ShoulderMusculoskeletal

Test protocol

Context

We will discuss here the Jerk Test, which is commonly used to identify posterior inferior glenohumeral instability and possible posterior labral involvement.

Posterior shoulder instability is less common than anterior instability, accounting for approximately 2% to 10% of all glenohumeral instability cases. The clinical presentation can often be vague and, given the overall lower incidence compared to other more common shoulder conditions, it is a frequently overlooked clinical diagnosis.

Posterior shoulder instability may be suspected following several causes, such as repetitive shoulder microtrauma, atraumatic causes—including initial ligamentous laxity—, and acute traumatic events.

Given the multitude of structures that contribute to posterior glenohumeral joint stability, a successful clinical diagnosis relies on a combination of thorough patient history, physical examination, and symptom presentation.

To determine the degree and direction of instability, certain provocation maneuvers can be performed, such as the Jerk Test.

Video of the Test

Execution

To perform the test, the patient is seated, and the examiner stabilizes the scapula with one hand. With the other hand, they bring the patient’s arm to 90° of abduction and add medial rotation of the shoulder. The physical therapist applies a posterior axial force along the humerus, then brings the patient’s arm into horizontal adduction while maintaining axial compression. The test is positive if the patient displays apprehension at posterior dislocation. This apprehension may be accompanied by pain or a sudden clunk if the humeral head slides out of the glenoid, and also when it repositions itself within the glenoid.

Clinical Value

In 2004, Kim and colleagues assigned it good clinical value in practice, with a sensitivity of approximately 89% and a specificity of approximately 85%.

However, there is limited evidence of the use of a single clinical test to diagnose posterior instability. Its use within a battery of tests may help build a clearer clinical picture (Sadi et al., 2020; Smith and Edwards, 2024). Sensitivity for detecting posterior inferior labral lesions would increase to 97% when the Jerk Test and the Kim Test are combined (Kim et al., 2004; Diaz-Heredia et al., 2017; Doehrmann and Frush, 2024).

Bibliography

Antoniou J, Duckworth DT, Harryman DT., 2nd Capsulolabral augmentation for the management of posteroinferior instability of the shoulder. J Bone Joint Surg Am. 2000;82:1220-1230.

Antosh, I. J., Tokish, J. M., & Owens, B. D. (2016). Posterior Shoulder Instability. Sports Health, 8(6), 520‑526.

Boyd HB, Sisk TD. Recurrent posterior dislocation of the shoulder. J Bone Joint Surg Am. 1972;54:779-786.

Doehrmann, R., & Frush, T. J. (2024). Posterior Shoulder Instability. In StatPearls. StatPearls Publishing.

Dhir, J., Willis, M., Watson, L., Somerville, L., & Sadi, J. (2018). Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability : A Systematic Review. Sports Health, 10(2), 141.

Díaz Heredia, J., Ruiz Iban, M. A., Ruiz Diaz, R., Moros Marco, S., Gutierrez Hernandez, J. C., & Valencia, M. (2017). The Posterior Unstable Shoulder : Natural History, Clinical Evaluation and Imaging. The Open Orthopaedics Journal, 11, 972‑978.

Fried J.W., Hurley E.T., Duenes M.L., et al. Return to play after arthroscopic stabilization for posterior shoulder instability—A systematic review. Arthrosc Sports Med Rehabil. 2021;3:e249–e256.

Hill AM, Bull AMJ, Richardson J, et al. The clinical assessment and classification of shoulder instability. Curr Orthop. 2008;22:208-225.

Kim, Seung-Ho, Jae-Chul Park, Jun-Sic Park, and Irvin Oh. “Painful Jerk Test: A Predictor of Success in Nonoperative Treatment of Posteroinferior Instability of the Shoulder.” The American Journal of Sports Medicine 32, no. 8 (December 2004): 1849–55.

Provencher MT, LeClere LE, King S, et al. Posterior instability of the shoulder: diagnosis and management. Am J Sports Med. 2011;39:874-886.

Robinson CM, Aderinto J. Recurrent posterior shoulder instability. J Bone Joint Surg Am. 2005;87:883-892.

Sadi, J., Torchia, E., Faber, K. J., MacDermid, J., Lalonde, C., Watson, L., Weber, M., & Wu, N. (2020). Posterior Shoulder Instability Classification, Assessment, and Management : An International Delphi Study. The Journal of Orthopaedic and Sports Physical Therapy, 50(7), 373‑380.

Smith, W. R., & Edwards, T. B. (2024). Posterior Shoulder Instability and Glenoid Bone Loss : A Review and a Free Bone Graft Technique. Journal of Clinical Medicine, 13(7).