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Our staff

jeff erenstone cpo
Founder, Owner, Head Clinician - Lake Placid
ABC Certified Prosthetist/Orthotist

I was born and raised in Lake Placid and feel fortunate to call the Adirondack North Country my home. I received a Bachelors of Science in Biology from the University of New Hampshire, and completed my Orthotic Practitioner Certificate program at Century College in White Bear Lake, Minnesota. I completed my Orthotic Residency at Northwest Orthotics and Prosthetics in Provo, UT where I continued to practice as a Certified Orthotist for several years. In 2006, I completed the Newington Prosthetic Certificate Program through the University of Connecticut. This led me to a residency with Mike Amrich CPO FAAOP of Boston Brace at Children’s Hospital in Boston, MA. Following the completion of my prosthetic residency, I worked as an orthotic design consultant for Spinal Technology in Yarmouth, Massachusetts before returning to the North Country to open our practice in 2007.

Over the last decade, I have built a practice specializing in custom and small production designs for adaptive athletes of all skill levels, from paralympians to amputees trying new sports. In 2018 I founded Operation Namaste, a 501(c)3 not-for-profit organization devoted to improving prosthetic care around the world, especially in Nepal. I am a member of the AOPA National Assembly Planning Committee and Tech. Committee, a member of the Mobility Saves Committee, and a regular volunteer for Camp No Limits.

Alex Trumper CPO
Owner, Head Clinician - Plattsburgh
ABC Certified Prosthetist/Orthotist

I joined the Mountain O&P team as the Practice Manager at the Plattsburgh office in 2015 and became co-owner in 2018. I’m originally from Canada and grew up in a suburb of Montreal, Quebec. In 2003 and 2006 respectively, I completed my Bachelor's degree in Kinesiology and a Master of Science degree in Biomechanics at McGill University. At that time, I decided to pursue the field of Orthotics in order to help individuals with injuries and/or disabilities. In 2007, I completed the Northwestern University Orthotics program and completed a 6 month research resident internship and 1 year Orthotic residency with Scheck and Siress, Chicago’s largest Orthotics and Prosthetics provider.


I returned to Northwestern University to complete the prosthetic portion of my education in 2008 and transitioned into a 1 year prosthetic residency. I was fortunate to have been awarded several scholarships (Gunther Gehl Scholarship, Dale Yasukawa Memorial Scholarship, named Best of the Resident Research series, and the Larry Lange travel award) for my resident research work and contributions to the field of Orthotics and Prosthetics. These awards allowed me to travel to Zacapa, Guatemala with the range of Motion Project (ROMP) to provide prosthetic care to patients that would not otherwise have access to these services. It was a truly amazing experience! I continued my career in Orthotics and Prosthetics with Scheck & Siress until July 2015.


After 9 great years in Chicago, my wife and I along with our two children decided to move back closer to our family in Montreal. The North Country has been a great fit for our lifestyle as we enjoy many outdoor activities such as hiking, biking and skiing.

michelle swanston cpo
ABC Certified Prosthetist/Orthotist
Malone Clinical Director

I grew up in Burke, NY. I had interned with this great group of practitioners in the past, and was pleasantly welcomed onto the staff in late May 2015 as an Orthotic Resident. I attended the University of Hartford where I matriculated through the Orthotic and Prosthetic B.S./M.S.P.O. program in Hartford, Connecticut. I received a Bachelors of Science in December of 2013, and later a Masters of Science in Prosthetics and Orthotics in May 2015. I completed my orthotic and prosthetic residencies as well as all board examinations while with Mountain O&P, and have become a fully Certified Prosthetist Orthotist.


I am a local of the North Country who grew up on a family-owned and operated dairy farm, and have a passion to work with people. I am happy to be back as well as eager and humbled to be able to share what I have learned as well as expand my knowledge with Mountain O&P and with those I encounter throughout my career. It is nice to come back home!

greg popp cPo
ABC Certified Prosthetist/Orthotist

Having had a varied employment history, including working at an Apiary, in the fishing industry in Alaska, landscaping, construction and several opportunities to travel in South America and Asia, I returned to school and earned my Bachelors of Science in Biology from SUNY Albany. My wife and I moved to Saranac Lake in the spring of 2008 and I began working at Mountain O&P in January of 2011 shortly before my first child, Rory, was born.

I then attended Northwestern's Feinberg School of Medicine’s Orthotics program in 2011-2012 and returned for Prosthetics in 2012-2013. I completed both of my residencies at MOPS and my family and I (wife Andrea, son Rory, and daughter Ada) are thrilled to continue to live and work in the Adirondacks. With a strong focus on patient care and continued adoption of the newest technologies in the field, I have had the honor of lecturing at numerous conferences across the US and was a keynote speaker at the NAMIC Additive Manufacturing Conference in Singapore in 2017. When not at work, you can find us hiking, riding or paddling on the many miles of trails and waterways in the Adirondack Park.

christopher poulin c.ped, cfo
ABC Certified Orthotic Pedorthist
ABC Certified Orthotic Fitter

I attended SUNY Canton to become an Occupational Therapy Assistant. I spent several years working in the Occupational Therapy Department at AMC Uihlein in Lake Placid as a COTA when the opportunity arose to work for Mountain O&P in 2008. I completed my Certification as an Orthotic Fitter, and then to further my education and to better serve the area became a Certified Pedorthist (C.Ped) through the Robert Palmer Institute in Elwood, IN.

Steve Halloran CFo
ABC Certified Orthotic Fitter
Prosthetic Peer Advisor

I grew up near Albany, NY. After serving in the U.S. Navy, I graduated from NYS Ranger school in Wanakena, NY. After numerous years as a Forestry Services Contractor in various parts of the country, I lost a leg due to a traumatic accident and became involved in the prosthetics industry. I now live in Westport, NY with my three sons and my wife Mary. My duties include the fitting and adjustment of orthotic and prosthetic devices, technical work fabricating orthotics and prosthetics, and serving as an orthotic and prosthetic assistant. As an amputee and Peer Advisor, I also provide firsthand insight for new amputees on what to expect, how to get the most of their prosthetic, and how to continue to live life to its fullest.

I find it very rewarding to see new amputees take their first steps, and I'm glad to be there for them. It's a feeling that never gets old.

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brittany williams
Practice Manager
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alyssa vannortwick
Plattsburgh Administrator
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jenarae beaudin
Malone Administrator
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jenna yeo
Malone Administrator
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debbie erenstone
Billing and Finance Supervisor
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amber g.
Administrator - Billing Specialist
Shane Kramer
Lab Manager
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