Kinematics and kinetics

Kinematics and kinetics

• Knee motion is predominantly in the sagittal plane. A limited - degree of rotation also occurs and increases as knee flexion increases. The normal range of motion is between 5° of hyper - extension and 135° of flexion. Magnetic resonance imaging (MRI) of cadaveric knees has revealed that, during knee flex - ion, a combination of rolling and sliding of the femur on the tibia occurs in addition to internal rotation of the tibia. This is because the larger medial femoral condyle rolls back less than the smaller lateral femoral condyle. This motion is facilitated by a more mobile lateral meniscus and la teral ligaments that are more lax in flexion. The biomechanical role of the patella is to function as a pulley for the quadriceps. It increases the power of the quad - riceps by increasing the le ver arm. It has the thickest articular cartilage in the body and is designed to withstand loads as high as 20 times body weight when jumping. Abnormal alignment, surface contour, soft-tissue constraints or muscle balance can r esult in patellar dislocation. Summary box 40.2 Biomechanics of the knee joint /uni25CF - /uni25CF /uni25CF /uni25CF

The femur has different anatomical and mechanical axes because of the offset of the proximal femur at the hip. These axes are the same in a normal tibia Knee motion is mainly in the sagittal plane with some rotation The patella acts as a pulley, increasing the lever arm of the quadriceps Loads of up to 20 times body weight are transmitted across the patella when jumping

Kinematics and kinetics

• Knee motion is predominantly in the sagittal plane. A limited - degree of rotation also occurs and increases as knee flexion increases. The normal range of motion is between 5° of hyper - extension and 135° of flexion. Magnetic resonance imaging (MRI) of cadaveric knees has revealed that, during knee flex - ion, a combination of rolling and sliding of the femur on the tibia occurs in addition to internal rotation of the tibia. This is because the larger medial femoral condyle rolls back less than the smaller lateral femoral condyle. This motion is facilitated by a more mobile lateral meniscus and la teral ligaments that are more lax in flexion. The biomechanical role of the patella is to function as a pulley for the quadriceps. It increases the power of the quad - riceps by increasing the le ver arm. It has the thickest articular cartilage in the body and is designed to withstand loads as high as 20 times body weight when jumping. Abnormal alignment, surface contour, soft-tissue constraints or muscle balance can r esult in patellar dislocation. Summary box 40.2 Biomechanics of the knee joint /uni25CF - /uni25CF /uni25CF /uni25CF

The femur has different anatomical and mechanical axes because of the offset of the proximal femur at the hip. These axes are the same in a normal tibia Knee motion is mainly in the sagittal plane with some rotation The patella acts as a pulley, increasing the lever arm of the quadriceps Loads of up to 20 times body weight are transmitted across the patella when jumping

Kinematics and kinetics

• Knee motion is predominantly in the sagittal plane. A limited - degree of rotation also occurs and increases as knee flexion increases. The normal range of motion is between 5° of hyper - extension and 135° of flexion. Magnetic resonance imaging (MRI) of cadaveric knees has revealed that, during knee flex - ion, a combination of rolling and sliding of the femur on the tibia occurs in addition to internal rotation of the tibia. This is because the larger medial femoral condyle rolls back less than the smaller lateral femoral condyle. This motion is facilitated by a more mobile lateral meniscus and la teral ligaments that are more lax in flexion. The biomechanical role of the patella is to function as a pulley for the quadriceps. It increases the power of the quad - riceps by increasing the le ver arm. It has the thickest articular cartilage in the body and is designed to withstand loads as high as 20 times body weight when jumping. Abnormal alignment, surface contour, soft-tissue constraints or muscle balance can r esult in patellar dislocation. Summary box 40.2 Biomechanics of the knee joint /uni25CF - /uni25CF /uni25CF /uni25CF

The femur has different anatomical and mechanical axes because of the offset of the proximal femur at the hip. These axes are the same in a normal tibia Knee motion is mainly in the sagittal plane with some rotation The patella acts as a pulley, increasing the lever arm of the quadriceps Loads of up to 20 times body weight are transmitted across the patella when jumping