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The Range Of Motion Specialists

JAS News: JAS vs PASS - The JAS Advantage


9/18/2015 -


 For 20 Years, Joint Active Systems (JAS) pioneered the use of Static Progressive Stretch (SPS) to restore lost Range of Motion with strong clinical results. JAS is the market leader in SPS therapy with over 250,000 clinical patient applications. Lately we have seen numerous comparisons from the manufacturer of products utilizing PASS technology claiming performance superiority.

Don’t believe everything you read!


Static Progressive Stretch utilizes the application of Stress Relaxation loading in a series of positional (displacement) changes. Stress Relaxation applies a stretching load to a viscoelastic material (connective tissue) to reach the displacement of a desired resistance. That displacement is held constant, so over time the connective tissue in a joint stretches and resistive loads drop (laxity). We then advance to a new point of resistance to eliminate the laxity. Once desired resistance is achieved, the new displacement is held constant until resistive load drops again. “Static Progressive Stretch” – SPS is this series of progressive repositioning against resistance. SPS mimics forces a therapist employs while manually stretching a joint. SPS is a highly efficient stretching force as shown in numerous published 
peer reviewed clinical studies.


Dr. Thomas Branch, founder of ERMI (End Range Motion, Inc.), published an article in 2003 defining PASS (Patient Actuated Serial Stretch) as a dynamic stretching method. The patient applies stretching force to their extremity in brief loads to their joint ‘End Range’ utilizing an ERMI device (Branch, et al, American Journal of Orthopedics, April 2003, Mechanical Therapy for Loss of Knee Flexion). ERMI devices as described in this article generate a high torque force (up to 500 ft/lbs) via a hydraulic load generated by the patient pumping the device. Applying shorter bursts of high intensity stretching force applied by the patient is very similar to Ballistic Stretching.  The American Academy of Orthopedic Surgeons (AAOS) warns against the use of Ballistic Stretching. 


Comparison of JAS SPS vs. PASS Cost Effectiveness*

 Why pay more for Range of Motion Therapy?  Following is a cost comparison of JAS SPS Knee rental costs versus PASS based therapy products:




JAS SPS Bidirectional Knee

$ 333*


PASS Flexion Knee - Unidirectional Only

up to $ 2,700*


 *Based on industry sources and published studies.



 We feel the best model for joint therapy is a Therapist manually tractioning an extremity. JAS’s unique geometry mimics the forces and loading vectors therapists employ. JAS geometry displaces the stretching force away from the joint surface (distraction).  The stretching force is applied ninety degrees to the extremity while it follows the articulation of the joint. JAS design also places the joint in a single plane with the drive tower and extremity throughout the rotation of the joint. We call this “Single Plane Positioning” It virtually eliminates joint malalignment. 

 Competitive designs use the joint surface as the fulcrum of forces applied to stretch the extremity, compressing the joint and articular cartilage. These compressive loads coupled with malalignment increase risk for the patient to experience discomfort and pain. Discomfort and pain result in poor patient compliance.  


 ERMI claims in studies that SPS units are only capable of generating anywhere from 5.2 foot pounds of force 7.6 foot pounds of force. They did not test a JAS unit!  In bench studies, JAS knee rental units generated 85-foot pounds of load at the joint position before device failure. These values compare favorably with Physical Therapy at 65-foot pounds of force. 

Joint Active Systems, Inc.
2600 S. Raney Street, Effingham, IL 62401