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

Nkansha-Andoh A, Meyers M, Russo D, Song K, Humbyrd C, Baxter JR: Using an istrumented insole to detect changes in Achilles tendon loading between pregnant women in their first trimester and pregnant women in their third trimester Annual Meeting of the Orthopaedic Research Society : 2025.

Song K, Kwon MP, Smith AK, Pohlig RT, Gravare-Silbernagel KM, Baxter JR: Sensor-measured Achilles tendon load is associated with plantar flexor dynamic function in Achilles tendinopathy Annual Meeting of the Orthopaedic Research Society : 2025.

Hullfish TJ, Kwon MP, Russo D, Boakye LAT, Humbyrd CJ, Baxter JR: Wearing an immobilizing boot after Achilles tendon rupture does not reduce tendon loading in all patients Annual Meeting of the Orthopaedic Research Society : 2025.

Godshall S, Kwon MP, Farber D, Ndu A, Humbyrd JC, Baxter JR, Boakye L: Wearable sensors measure wear time and step count in immobilizing boots for Achilles tendon rupture Annual Meeting of the Orthopaedic Research Society : 2025.

Meyers M, Nkansha-Andoh A, Russo D, Song K, Durnwald C, Humbyrd C, Baxter JR: Pregnancy gait biomechanics using markerless motion capture Annual Meeting of the Orthopaedic Research Society : 2025.

Strand KS, Hullfish TJ, Wagner MM, Baxter JR: Achilles subtendon morphology identified via isolated muscle stimulatios is sensitive to ankle angle Annual Meeting of the Orthopaedic Research Society : 2025.

Seymore K, Baxter JR, Silbernagel KG, Cone S: Achilles tendon shear wave speed during gait relates to lower limb function and strength in adolescents Americas Society of Biomechanics 2024 : 2024.

Wagner M, Vitale F, Baxter JR: High-density surface electromyography to monitor neuromusuclar activity across joints affected by common musculoskeletal pathologies American Society of Biomechanics Annual Meeting : 2024.

Song K, Smith A, Kwon M, Silbernagel KG, Baxter JR: Two weeks of Achilles tendon loading monitoring by instrumented insole is associated with plantarfelxor function American Society of Biomechanics Annual Meeting : 2024.

Meyers M, Humbyrd C, Baxter JR: Camera-based system to track arch height index during pregnancy and postpartum American Society of Biomechanics Annual Meeting : 2024.

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Academic Contact Information

3450 Hamilton Walk
372A Stemmler Hall
Philadelphia, PA 19104
Phone: 215-898-7395