Brent is rehabilitating an injured right knee. He is performing isokinetic (constant velocity) knee extensions against resistance provided by a Cybex machine. At the instant in question, his thigh is horizontal and knee is flexed 73 degrees below the horizontal. The Cybex machine exerts an external force of 415N perpendicular to the calf long axis at a distance of 54cm from the knee joint center. The weight of this calf + foot is 56N. Assume the center of mass of the calf + foot is halfway between the knee joint center and the point of the application of the external force from the Cybex machine. The angle of pull of the patellar tendon on the tibia is 6 degrees. The moment arm of the patellar tendon force about the knee joint center is 4.3cm.

Compute the magnitude of the patellar tendon force

Compute the compressive and shear components of the tibiofemoral joint force.

Compute the magnitude of the tibiofemoral joint force and its direction relative to the long axis of the tibia.

Transcribed Image Text:

73° 799 56N 415 N 6° 73° 799 56N 415 N 6°