David is a 25-year-old insurance salesman and avid “weekend warrior” water-skier

Question

David is a 25-year-old insurance salesman and avid “weekend warrior” water-skier. He is skiing behind a powerful speedboat with both feet strapped into a wake board when the boat driver hits the throttle. David starts to fall awkwardly to his right. He resists the fall and digs into the board with his right foot. Suddenly he feels an extremely painful, incapacitating pop below his right gluteal region and falls into the water.

David is unable to swim; it feels as if his right lower extremity is paralyzed. Fortunately, he is wearing a life vest, and within minutes he is pulled into the boat and rescued. Back at the dock, he finds he cannot flex his knee at all but is able to get around by locking his quads, “hiking” his hip (knee in extension), and doing an “abduction swing” to place his right foot forward while leaning on a friend for support. He cannot sit on his right side. The next evening, massive bruising appears on the entire posterior surface of his thigh and knee. Three weeks later, the bruising and swelling finally begin to resolve, but David can still feel a ball of muscle behind his right knee.

One month post-injury, David is still unable to flex his knee. He visits an orthopedist, who immediately schedules him for surgery.

David sustained a complete avulsion of his hamstring tendons from their origin on the ischial tuberosity. Hamstrings are part of what class of lever at the knee?

David sustained a complete avulsion of his hamstring tendons from their origin on the ischial tuberosity. Hamstrings are part of what class of lever at the knee?

The hamstrings are not part of the lever system. The hamstrings are part of a second-class lever, where the load is between the applied force and the fulcrum. The hamstrings are part of a first-class lever, where the fulcrum is between the applied force and the load. The hamstrings are part of a third-class lever, where the applied force is between the load and the fulcrum.

Explanation / Answer

There are three hamstring muscles which are-- biceps femoris, semitendinous and semimembranous ,at the back of the thigh. These muscles mainly help in leg movement like bending the knees and extending our legs. Sometimes,due to over stressing or a sudden sharp jerk , the hamstring muscle tendon completely tears away from the bone . This is called avulsion injury.

In my view, for the above question, the hamstrings are not a part of the lever system.

Reason -- Hamstrings are technically the tendons on either end of the posterior thigh muscles. All heads of hamstring originate on the ischial tuberosity of the pelvis, except the biceps femoris short head which arises from the posterior femur. The lateral hamstrings run inferior and lateral and insert proximal lateral tibia. The medial hamstring runs inferior and medial and insert on the proximal medial tibia and fibula .

So, the hamstring does not fit into the ideal definition of a lever.

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