Clamshells Exercise

Exercises that mimic special tests series.

This series highlights some exercises that mimic positions of special tests. Recognizing this crossover between the interventions we use, and the research-supported symptom patterns evoked can help us guide intervention, exercise modification, and diagnosis.

Clamshells Exercise: Side-lying clams do a great job at combining hip extension, abduction, and ER in a way that many standing exercises for these groups do not. I personally like to use it as an early phase strengthening exercise or a good home exercise program option if hip ER strength is a goal. As a healthy young person, I feel a muscular burn on my posterolateral hip after a set of these at a challenging resistance. However, from time-to-time I have had patients report a burning in their deep posterior gluteal region during clamshells.

Active Piriformis test: with patient in side-lying (test-leg superior), the patient plants their test-side foot on the table and the PT resists hip abduction and external rotation. This test causes contraction of the deep external rotators which can potentially recreate localized or radicular symptoms consistent with piriformis syndrome (Sensitivity 78%, Specificity 80%).

I would be interested to see if changing the hip flexion angle during the clamshell exercise would modify symptoms in this subset of the patients I treat. I have to admit, when I hear a deep glute symptom report with clams, I often substitute an alternative exercise without experimenting. Comment below if you have noticed this pattern, and how you address it. Am I being overly cautious by avoiding reproduction of deep glute symptoms?

If deep gluteal symptoms are produced during the clamshell exercise, consider the below test to further evaluate for piriformis syndrome (along with taking a thorough subjective history and standard PT exam as indicated).

"Seated Piriformis test: with patient in sitting, the PT passively holds the knee in extension and moves the hip into adduction and internal rotation. This test elongates the deep external rotators which can potentially compress the sciatic nerve to recreate localized or radicular symptoms (Sensitivity 52%, Specificity 90%).

Best diagnostic accuracy to identify piriformis-mediated symptoms (compared to endoscopic findings) was achieved when using the above two tests in a cluster (Sensitivity 91%, Specificity 80%)."

Mary Kate Halligan, PT, DPT

Martin HD, Kivlan BR, Palmer IJ, Martin RL. Diagnostic accuracy of clinical tests for sciatic nerve entrapment in the gluteal region. Knee Surgery, Sports Traumatology, Arthroscopy. 2014 Apr;22(4):882-8.