Calypso study

Superiority over HTO in Pivotal Study for FDA


Achieved by ISA


Achieved by HTO

Data on file at Moximed.

An overwhelming majority of study participants receiving the ISA experienced clinically meaningful improvement in pain and function by two years after the procedure.

pain relief

96% vs. 88%

ISA responder rate vs. HTO

Functional improvement

92% vs. 81%

ISA responder rate vs. HTO

Patients rapidly returned to activity and reported dramatic improvement compared to their pre-ISA treatment status.


days to full weight bearing.


reduction in knee pain.


improvement in knee function.

Diduch DR, Crawford DC, Ranawat AS, Victor J, Flanigan DC. Implantable Shock Absorber Provides Superior Pain Relief and Functional Improvement Compared With High Tibial Osteotomy in Patients with Mild-to-Moderate Medial Knee Osteoarthritis: A 2-Year Report. CARTILAGE. 2023;0(0). doi:10.1177/19476035231157335.

Results from the clinical study resoundingly met pre-defined safety criteria.


freedom from safety endpoint event.


freedom from conversion to HTO or arthroplasty.*


freedom from implant integrity event.**

*One patient in the ISA group converted to UKA. **There were no device mechanical failures in the ISA group. One screw in the ISA group was deemed to have partially backed out; device remains in situ without further sequelae.

Data on file at Moximed.

The ISA was designed to help knee OA patients return to activities important to them.

In the clinical study, patients self-selected their desired activity, then tracked their ability to perform that activity over the course of their recovery from the procedure.

man and girl skateboarding

Lower impact exercise

The most desired activities were low impact cardiovascular exercises, such as cycling or elliptical training (57.5% of patients).

women running

Medium to higher impact activities

Running, jogging, and hiking were selected by 54.8% of patients.

women exercising

Resistance training and dynamic sports

26.0% wanted to resume weightlifting, squats, or leg presses, and 8.2% wanted to return to contact sports, including football, basketball, and soccer.

The most common adverse reaction in the study was pain, with 5% of ISA patients and 36% of HTO patients reporting pain after the procedure (p<0.001).

Early onset OA meant that by my early 30s I was in too much pain to stand and kick a soccer ball to my four year old. I tried every non-surgical intervention without success. After the ISA surgery, I’ve been able to return to running, skiing, and I’ve even taken up kickboxing. I can push myself hard enough to irritate my knee, and getting smacked on the device feels a lot like getting hit on the funny bone. But this surgery has given me my life back and it allows me live normally without thinking about my knee, while vastly exceeding my expectations for how active I can be. I’d do it again in a heartbeat.

Zach A., participant in previous study of the ISA
Five years after surgery

Study participants who received the ISA were able to get back on their feet, and to weight bearing activity, up to 7 times faster than participants who received HTO.

woman and boy roller skating

Days to Weight Bearing

Partial Weight Bearing, p < 0.001


4 days


28 days

Full Weight Bearing, p < 0.001


13 days


58 days

As with any surgery, individual results may vary. Most side effects recorded in the study were mild to moderate, and included catching/pulling sensation, inability to perform certain tasks such as lifting/exercising, dissatisfaction with the procedure, cellulitus, surgical site infection, knee pain, kinesiophobia, and scar formation/adhesions. Most side effects resolved without further sequelae, and in certain instances the implant was removed.

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