Smaller Knee Flexion Angles Research Articles

Three-body segment dynamic model of the human knee.

In this paper, a two-dimensional, three-body segment dynamic model of the human knee is introduced. The model includes tibio-femoral and patello-femoral articulations, and anterior cruciate, posterior cruciate, medial collateral, lateral collateral, and patellar ligaments. It enables one to obtain dynamic response of the knee joint to any one or combination of quadriceps femoris, hamstrings, and gastrocnemius muscle actions, as well as any externally applied forces on the lower leg. A specially developed human knee animation program is utilized in order to fine tune some model parameters. Numerical results are presented for knee extension under the impulsive action of the quadriceps femoris muscle group to simulate a vigorous lower limb activity such as kicking. The model shows that the patella can be subjected to very large transient patello-femoral contact force during a strenuous lower limb activity even under conditions of small knee-flexion angles. The results are discussed and compared with limited data reported in the literature.

Reflex stiffness of man's anti-gravity muscles during kneebends while carrying extra weights

The effective lumped stiffness and damping ratio of the human leg system was determined from measurements of parallel and antiparallel-mode oscillations while standing on a linear spring. Knee flexion angle was held fixed in each trial, and varied systematically from 0° to 75°. At each knee angle, subjects carried weights up to twice body weight on their shoulders to determine the effect of increasing muscle force. For small knee flexion angles (θ ≤ 30°), reflex stiffness was independent of muscle force, but rose slightly with muscle force for large flexions. The damping ratio was calculated to be 0.34, showing the underdamped character often reported for skeletomotor feflex mechanisms. Leg stiffness measured in this way is consistent with measurements taken during human running.