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Dr. Allyn Smith is the Founder and Clinical Director of Performance Plus Rehabilitation Center, serving Northwest Missouri with integrated chiropractic and physical therapy care for more than 30 years.

After graduating from Northwestern Chiropractic College in 1991, Dr. Smith established his St. Joseph practice in 1993. His commitment to advancing patient care led to the development of a unified chiropractic and physical therapy model, which evolved into Performance Plus Rehabilitation Center in 2001. Since opening in 1994, he has guided the organization’s growth into a structured, evidence-based rehabilitation center focused on biomechanical precision, functional restoration, and long-term outcomes.

Dr. Smith remains actively involved in the Missouri State Chiropractic Physicians Association and the American Chiropractic Association, contributing to professional leadership at both the state and national levels. He is also a frequent speaker on health optimization, structural wellness, and stress physiology.

A former All-American triathlete and competitive cyclist, Dr. Smith brings a performance-driven philosophy to patient care and leadership. His vision for Performance Plus centers on improving mobility, resilience, and quality of life for individuals and families throughout St. Joseph, Cameron, and the surrounding communities.

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Dr. Aaron Jones has been an integral part of Performance Plus Rehabilitation Center for over a decade, serving as the esteemed Physical Therapy Director since 2008. Dr. Jones is a distinguished alumnus of Missouri State University, where he dedicated himself to the study of physical therapy and successfully attained his Doctor of Physical Therapy degree.

Within the realm of physical therapy, Dr. Jones exhibits a fervent passion for the comprehensive treatment of sports injuries, shoulder injury/dysfunction, and complex neurological conditions such as stroke, spinal cord injury, and Parkinson’s Disease. His unwavering commitment to staying up-to-date of the latest advancements in his field ensures that his patients receive the highest standard of care.

Beyond his professional pursuits, Dr. Jones is an avid advocate for physical fitness, dedicating his time to weight training, hiking, and other outdoor activities. As a devoted family man, Dr. Jones and his family actively engage in a myriad of activities that promote a healthy lifestyle. Through their collective efforts, they strive to instill the values of wellness and physical activity in their children, fostering a holistic approach to health within their household. Dr. Jones also enjoys woodworking.

Dr. Jones exemplifies his unwavering dedication to his profession by leading through example, consistently encouraging his patients to embrace an active and wholesome lifestyle at every stage of life. His genuine care and passion for physical therapy are evident in the personalized attention and guidance he provides to each individual under his care.

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Dr. Hannah Spiegel is a Doctor of Physical Therapy who joined Performance Plus in 2025. Originally from St. Joseph, MO, she attended Missouri Western State University where she earned her Bachelors of Science in Health and Exercise Science in 2022. She then pursued her graduate degree at the University of Saint Mary in Leavenworth, KS, where she graduated as a Doctor of Physical Therapy in 2024. Her top priority as a Physical Therapist is ensuring her patients receive the care they deserve by utilizing evidence-based practice to improve their function and quality of life.

Dr. Spiegel provides pelvic floor rehabilitation for both female and male patients. Specialized, results-driven care for pelvic dysfunction, core instability, incontinence, and post-surgical recovery.

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Dr. Joshua Middendorf has more than 13 years of experience in chiropractic care, with a clinical focus on the evaluation and treatment of spine and musculoskeletal conditions.

He earned his Bachelor of Science from Northwest Missouri State University and completed his Doctor of Chiropractic degree at Logan University in Chesterfield, Missouri, one of the leading chiropractic institutions in the country.

Dr. Middendorf is trained in a range of evidence-based chiropractic techniques used to address back pain, neck pain, joint dysfunction, and mobility limitations. His approach emphasizes thorough evaluation, precise treatment, and individualized care plans designed to improve function and support long-term musculoskeletal health.

Prior to joining Performance Plus Rehabilitation Center in 2016, Dr. Middendorf owned and operated a chiropractic practice for five years. At Performance Plus, he works within an integrated rehabilitation model, collaborating with physical therapists to support comprehensive spine and orthopedic care.

Originally from Northeast Missouri, Dr. Middendorf maintains strong ties to the region and serves patients throughout St. Joseph and Northwest Missouri.

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Dr. Derek Kendall is an esteemed Doctor of Physical Therapy recognized for his advanced clinical expertise and commitment to exceptional patient care. He joined Performance Plus Rehabilitation Center in 2021, bringing with him a strong academic foundation and a passion for elevating patient outcomes.

A St. Joseph, Missouri native, Dr. Kendall is deeply connected to the community he serves. He graduated from Benton High School before earning his Bachelor’s degree in Exercise and Movement Science from Missouri State University. He went on to complete his Doctor of Physical Therapy at Rockhurst University—an institution known for its rigorous, evidence-based clinical training.

Dr. Kendall is dedicated to helping patients restore function, enhance mobility, and achieve long-term wellness through individualized, research-driven treatment. His clinical approach reflects the highest standards of modern physical therapy.

Outside of his practice, he maintains an active lifestyle and enjoys golfing, strength training, and spending time outdoors.

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Dr. Aaron Clary grew up in a family rooted in manufacturing and labor, giving him firsthand insight into the toll demanding work takes on the body. Before becoming a chiropractor, he worked those same jobs—an experience that shaped his genuine empathy and practical approach to care.

After earning his Doctor of Chiropractic degree from Cleveland University–Kansas City, Dr. Clary built a reputation for excellence in the Kansas City area, where he was repeatedly recognized as one of the Best Chiropractors in Lee’s Summit. Now back home at Performance Plus in St. Joseph, he brings that same skill and integrity to the community he knows best.

Patients describe him as calm, skilled, and patient-focused. Known for his gentle yet effective hands-on care, Dr. Clary combines real-world experience with clinical precision to help patients recover from injury, manage chronic pain, and restore balance, strength, and mobility. In addition to spinal care, he is highly regarded for his expertise in treating extremities—shoulders, wrists, knees, ankles, and feet—joints essential to daily life but often overlooked.

Whether you’re an injured worker, an active parent, or someone seeking long-term relief, Dr. Clary offers whole-body chiropractic care to restore movement, strength, and overall health. He also provides pediatric chiropractic services for children of all ages, addressing posture, growing pains, and sports-related injuries. With a whole-family approach, Dr. Clary helps kids, parents, and grandparents alike stay active, resilient, and well.

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Dr. Rick is a 1991 graduate of Cleveland Chiropractic College and is Missouri State licensed and National Board Certified in Chiropractic. For over 30 years, he has provided evidence-based chiropractic care grounded in biomechanical precision, structured treatment progression, and measurable functional outcomes. His clinical approach emphasizes spinal alignment, neuromuscular control, and long-term durability. He has also completed advanced training in acupuncture at the International Academy of Medical Acupuncture as an adjunctive modality when clinically indicated.

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Dr. Justin Casey has been part of the Performance Plus Rehabilitation Center team since 2014, bringing over a decade of experience and a patient-focused approach to chiropractic care. He earned his BA in Psychology from Harding University in Searcy, Arkansas, and his Doctor of Chiropractic degree from Cleveland Chiropractic College in Overland Park.

Dr. Casey has a special interest in treating headaches and migraines, helping patients find lasting relief and improved quality of life. He also has advanced training in Graston Technique, kinesio taping, and activator methods, allowing him to tailor treatments to each individual’s needs.

Outside the clinic, Dr. Casey enjoys watching soccer, traveling, and scuba diving. He values time with his wife, Ellen, and their dog, Raya. Dedicated to giving back, he also volunteers with the 501st Legion costuming group, supporting local charities and community events.