Soft tissue injury is very common and associated with pain, tissue swelling and even malformation if not treated on time. Treating methods include cryotherapy, electrical therapy, ultrasound therapy and anti-inflammatory drug, but none of them is completely satisfying. In this work, for a better therapeutic effect, drug therapy and pulsed electromagnetic field (PEMF) therapy were combined. We constructed a drug delivery system using the tetra-PEG/agar hydrogel (PA). By incorporating Fe 3 O 4 NPs into the hydrogel network, a magnetism-responsive property was achieved in the system. The cytotoxicity and in vivo study showed a good biocompatibility of the PA/Fe 3 O 4 hydrogel. A magnetism-controlled release was attained by the incorporation of Fe 3 O 4 . Finally, in vivo study showed a better performance of the DS-loaded PA/Fe 3 O 4 compared with the commercially available DS ointment regarding the recovery of the injured soft tissue. Therefore, this magnetism-responsive hydrogel may represent a promising alternative to treat soft tissue injury.

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Objective The purpose of this study was to investigate the effects of different durations of static progressive stretching (SPS) on posttraumatic knee contracture in rats, including range of motion (ROM), gait analysis, myofibroblast proliferation, and collagen regulation. Methods The posttraumatic knee contracture model was established, and male Wistar rats were randomly divided into the 20-minute SPS treatment, 30-minute SPS treatment, 40-minute SPS treatment, untreated, immobilization, and control groups. At weeks 0, 1, 2, and 4 of treatment intervention, joint ROM and gait were measured and compared. Knee joint samples stained with hematoxylin and eosin and Masson trichrome were used to observe alterations in pathological structures. Collagen density and cell numbers in the posterior joint capsule were used to assess joint capsule fibrosis and inflammation. Immunohistochemistry was used to detect type I collagen and α-smooth muscle actin expression. Results The S30 group improved the most; ROM, stance, mean intensity, print area, and stride length were 115 (SD = 5) degrees, 0.423 (SD = 0.074) seconds, 156.020 (SD = 7.952), 2.116 (SD = 0.078) cm2, and 11.758 (SD = 0.548) cm, respectively. The numbers of myofibroblasts, fibroblasts, and inflammatory cells decreased, and collagen proliferation was significantly suppressed in the S30 group compared with the other groups. Conclusion S30 significantly improved posttraumatic knee contracture in rats, with reduced type I collagen and α-smooth muscle actin expression, decreased the numbers of myofibroblasts and inflammatory cells, suppressed fibrotic and inflammatory changes in the joint capsule, and increased joint mobility. This study provided basic evidence for an optimal standard-of-care treatment approach for posttraumatic knee joint contracture in rats, which may have significance for humans.