Objective To study the short-term variation patterns of graft viscosity after anterior cruciate ligament reconstruction (ACLR) surgery. Methods Six male New Zealand rabbits were selected. The ACLR animal model of unilateral knee was made with Achilles tendon as the graft. The experimental rabbits were euthanized 15 days after ACLR surgery, with removal of the graft, healthy anterior cruciate ligament (ACL) and Achilles tendon. The cross-sectional area and viscosity coefficient of the graft were measured, and the creep experiments were carried out under equilibrium conditions of 0.1 MPa and 1 MPa, respectively. The viscosity coefficent was calculated. Variation patterns of graft viscosity were summarize. The grafts were compared with healthy ACL. Results The cross-sectional area of the graft increased slowly within 15 days after ACLR surgery. The viscosity of ACL and graft changed nonlinearly. The viscosity coefficient was quite different under different stresses. The viscosity coefficient of the graft decreased with the time after ACLR surgery, which was more obviously under the condition of low stress. Conclusions The results are helpful to guide the implementation of early postoperative rehabilitation plan after ACLR surgery .

Objective To study the effects of prosthetic alignment on internal contact mechanical characteristics of intact knee joint for transfemoral amputees. Methods The gait experiment of transfemoral amputees was performed under different alignment conditions, and the differences of lower limb motion and ground reaction force (GRF) were analyzed and compared with those of the non-amputees. The three-dimensional （30） finite element model of knee joint was build and used to analyze the effect of alignments of socket adduction and abduction on internal contact mechanical characteristics between femur cartilage, tibia cartilage and meniscus. Results For knee joint of the non-amputees, contact force was mainly concentrated on the medial sides at the moment of the first GRF peak, while contact force was mainly concentrated on the lateral sides at the moment of the second GRF peak. However, for intact knee joint of the transfemoral amputees, contact force was mainly concentrated on the medial side at the moment of two GRF peaks. The stress of the medial meniscus, contact force and contact area between the medial meniscus and cartilage all obviously increased under the alignment of 6° socket adduction. Conclusions Compared with non-amputees, the incidence of knee osteoarthritis (OA) in amputees was higher, which was related to the long-term overload of the medial knee joint. The alignment of socket adduction may increase the risk of knee OA in the intact side of transfemoral amputees. In clinic, excessive adduction of the socket should be avoided during prosthetic alignment.