Janus Piezoelectric Nanocomposite Hydrogel for Efficient Tendon Repair, Motion Monitoring and Intelligent Knee Rehabilitation Assessment

ABSTRACT Continuous assessment of knee stability is crucial for guiding postoperative rehabilitation and evaluating tissue healing, particularly in dynamic disorders such as patellofemoral instability, where abnormal rotation and varus‐valgus loading may occur unexpectedly. Current clinical evaluations remain subjective or intermittent, while epidermal wearable sensors are vulnerable to skin motion artifacts and cannot directly report periarticular soft‐tissue mechanics. Herein, an exosome‐loaded polyvinyl alcohol Janus piezoelectric nanocomposite hydrogel is developed for knee‐related rehabilitation monitoring and general tendon repair under ultrasound stimulation. This system features a biomimetic bilayer: a soft, self‐healing layer containing exosomes adheres to injured tissues to accelerate microenvironment repair, whereas a mechanically stronger layer (1.2 Mpa) with quaternary ammonium chitosan‐modified MoS 2 nanosheets (d 33 = 24 pC/N) serves as an implantable sensor, generating electrical signals upon deformation. Coupled with a customized convolutional neural network‐transformer framework, eight complex knee‐motion patterns (internal/external rotation and varus/valgus at 0° and 90° flexion) are classified with high accuracy above 99.4%. A prototype quantitative patellofemoral biomechanics and function scoring platform is established to dynamically evaluate rehabilitation progress. The relative collagen deposition rate reached 95.3% after treatment. Ex vivo human cadaveric and in vivo animal studies demonstrate that this therapeutic sensing‐material strategy holds promising potential for precision rehabilitation applications.