Josh R Baxter, PhD

faculty photo
Assistant Professor of Orthopaedic Surgery
Director, Human Motion Laboratory, Hospital of the University Of Pennsylvania
Department: Orthopaedic Surgery

Contact information
3450 Hamilton Walk
372A Stemmler Hall
Philadelphia, PA 19104
Office: 215-898-7395
Education:
BS (Exercise Science)
Central Washington University, 2007.
MS (Nutrition and Exercise Science)
Oregon State University, 2009.
PhD (Kinesiology - Biomechanics)
Pennsylvania State University, 2012.
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Description of Research Expertise

My research is focused on improving rehabilitation loading protocols to treat musculoskeletal injuries. In orthopaedics, we leverage mechanical loads as a way to treat musculoskeletal injuries. For example, following a tendon rupture, an orthopaedic surgeon will repair the tendon using suture to restore the mechanical integrity of the tissue to bare mechanical loads. While these treatments stabilize the tissue while biologic healing restores tissue function, our understanding of the post-operative loading environment that promotes healing is less understood. My research is exploring the rehabilitation period following musculoskeletal injury and surgical treatment to safely promote tissue healing and improve patient outcomes.

My group uses preclinical and clinical models to identify what loads are therapuetic for tissue healing and what loads are injurious. This is critical because it works within the current reimbursement structure of musculoskeletal care. Once we identify therapuetic loading profiles, we will be able to deliver precision rehabilatiton through reimbursable physical therapy pathways to maximize healing and patient outcomes.

My group is currently performing 5 funded projects:
1 - Modifying muscle remodeling following Achilles tendon ruptures funded by the NIH/NIAMS K01-AR075877. The goal of this study is for the PI to receive mentoring and training in small animal models, imaging, and muscle physiology to develop clinically viable treatment paradigms for Achilles tendon ruptures.
2 - Tendon loading profiles that promote healing in Achilles tendinopathy funded by the NIH/NIAMS R01-AR078898. The goal of this study is to determine rehabilitation loading profiles and ultrasound imaging biomarkers that explain tendon healing and functional outcomes in patients with mid-substance Achilles tendinopathy.
3 - Linking structural changes and functional outcomes following Achilles tendon rupture funded by the American Orthopaedic Foot and Ankle Society. The goal of this study is to link tendon loading throughout healing with muscle-tendon structure and functional outcomes in patients who undergo surgical repair for acute Achilles tendon ruptures.
4 - Precision rehabilitation to restore plantar flexor function following Achilles tendon rupture repair funded by the NIH/NIAMS R21-AR081497. The goal of this study is to identify therapeutic loads that can be translated to the clinic and guide precision rehabilitation using a small animal model.
5 - Defining the neuromechanical mechanisms of Achilles tendinopathy funded by the NIH/NIAMS R01-AR081062. The goal of this study is to measure plantar flexor neuromechanics using our innovative high-density surface electromyography sensors custom developed at Penn to determine how rehabilitation exercises can be optimized to guide treatment and improve outcomes in patients with Achilles tendinopathy.

Selected Publications

Scattone Silva R, Song K, Hullfish TJ, Sprague A, Silbernagel KG, Baxter JR: Patellar Tendon Load Progression during Rehabilitation Exercises: Implications for the Treatment of Patellar Tendon Injuries. Medicine and Science in Sports and Exercise October 2023.

Fogarty NL, Johnson T, Kwok B, Lin A, Tsinman TK, Jian X, Koyama E, Han L, Baxter JR, Mauck RL, Dyment NA: Reduction in postnatal weight-bearing does not alter the trajectory of murine meniscus growth and maturation. Journal of Orthopaedic Research October 2023 Notes: 10.1002/jor.25711.

Kwon MP, Hullfish TJ, Humbyrd CJ, Boakye LAT, Baxter JR: Wearable sensor and machine learning estimate tendon load and walking speed during immobilizing boot ambulation. Scientific Reports 13(1): 18086, October 2023 Notes: doi:10.1038/s41598-023-45375-x.

Song K, Cone SG, Zellers JA, Thelen DG, Baxter JR.: Tracking day-to-day Achilles tendon loading progression during rupture recovery. North American Conference on Biomechanics; 2022; Ottawa, ON, Canada. Aug 2023 Notes: poster presentation.

Song K, Hullfish TJ, Scattone Silva R, Silbernagel KG, Baxter JR.: Markerless motion capture estimates of lower extremity kinematics and kinetics are comparable to marker-based across 8 movements. American Society of Biomechanics Annual Meeting; 2023; Knoxville, TN, USA. Aug 2023 Notes: Podium presentation.

Song K, Hullfish T, Scattone R, Silbernagel K, Baxter JR: Markerless motion capture estimates of lower extremity kinematics and kinetics are comparable to marker-based across 8 movements. Journal of Biomechanics 157: 111751, Aug 2023 Notes: https://doi.org/10.1016/j.jbiomech.2023.111751.

Song K, Hullfish TJ, Silva SR, Silbernagel KG, Baxter JR: Markerless motion capture estimates of lower extremity kinematics and kinetics are comparable to marker-based across 8 movements. Journal of Biomechanics 157: 111751, Aug 2023 Notes: doi: 10.1016/j.jbiomech.2023.111751.

Song K, Scattone R, Hullfish T, Silbernagel K, Baxter JR: Patellofemoral Joint Loading Progression Across 35 Weight-Bearing Rehabilitation Exercises and Activities of Daily Living. American Journal of Sports Medicine 51(8): 2110-2119, Jul 2023.

Phan V, Song K, Silva RS, Silbernagel KG, Baxter JR, Halilaj Eni: Seven Things to Know about Exercise Monitoring with Inertial Sensing Wearables. TechRxiv June 2023 Notes: preprint doi: 10.36227/techrxiv.23296487.v1.

Song K, Cone SG, Zellers JA, Thelen DG, Baxter JR: Day-to-day loading progression in repaired Achilles tendon corresponds to real-world events of tendon health. Orthopaedic Research Society Tendon Section Conference; 2022; Philadelphia, PA, USA. Feb 2023 Notes: Poster presentation.

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Last updated: 02/12/2024
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