Investigating the biomechanics for the PCL ruptured or reconstructed patients during walking, jogging, cutting, jumping. To establish a knee joint biomechanical evaluation model to quantify and evaluate the plantar pressure information under dynamic load-bearing state after PCL fracture. Provide a precise basis for the biomechanical state of the knee, and establish a clinically practical automatic analysis of plantar pressure information and an expert diagnostic system.

Background: The posterior cruciate ligament (PCL) is an essential structure in knee stabilization. Knee cartilage degeneration after a PCL injury has been reported in several studies. Understanding the changes in movement patterns of patients with PCL ruptures could help clinicians make specific treatment protocols to restore patients' sporting ability and prevent joint degeneration. However, the kinematics and kinetics of the lower limb in patients with PCL injuries are still not clear.

Methods: Three-dimensional gait analysis system, force plate, electromyography will be used for 55 healthy male participants (control group) and 55 male patients with isolated PCL-deficiency (PCL-d group) during walking, jogging, cutting, jumping. Repeated measurement two-factor analysis of variance will be performed to determine differences between involved and uninvolved legs in the PCL-d group and control group at different rehabilitation times (prior reconstruction surgery, 6 months, and 1-year post PCL reconstruction surgery). Three-dimensional gait analysis and computer-aided analysis technology of plantar pressure information were used to study the changes of PCL after fracture and reconstruction. Based on the plantar pressure information, the movement parameters, and individual attribute parameters, establish a knee joint biomechanical evaluation model to quantify and evaluate the plantar pressure information under dynamic load-bearing state after PCL fracture. Provide a precise basis for the biomechanical state of the knee, and establish a clinically practical automatic analysis of plantar pressure information and an expert diagnostic system.

Inclusion Criteria:

• age of 18-45 years old
• Isolated PCL rupture patients: The inclusion criteria included an isolated PCL rupture of at least 3 months' duration.
• Healthy volunteers: no history of neuro or musculoskeletal system injury that may affect the movements.

Exclusion Criteria:

• additional knee ligament or meniscal damage
• severe damage to the ipsilateral hip, ankle joint, or contralateral lower limb (ligament ruptures or bone fractures)
• age >50 years (to avoid age-induced osteoarthritis interference)
• any cartilage injury grade >2 according to the Outerbridge classification
• Tegner score18 <3

Inclusion：age of 18-45 years old. Healthy volunteers: no history of neuro or musculoskeletal system injury that may affect the movements. Isolated PCL rupture patients: The inclusion criteria included an isolated PCL rupture of at least 3 months' duration. The exclusion criteria were (1) additional knee ligament or meniscal damage; (2) severe damage to the ipsilateral hip, ankle joint, or contralateral lower limb (ligament ruptures or bone fractures); (3) age >50 years (to avoid age-induced osteoarthritis interference); (4) any cartilage injury grade >2 according to the Outerbridge classification; and (5) Tegner score18 <3.