During a weight lifting competition, Jack suffered an avulsion fracture to his p

Question

During a weight lifting competition, Jack suffered an avulsion fracture to his patella. This means the muscle pulled the bone apart and a small piece of bone broke away from the patella but remained attached to the quadriceps tendon.

(20 pts) During a weight lifting competition, Jack suffered an avulsion fracture to his patella. This means the muscle pulled the bone apart and a small piece of bone broke away from the patella but remained attached to the quadriceps tendon 3. a. (5 pts) If the avulsion had a cross sectional area of 0.002m2, what was the force required to fracture the bone? (2 pts) In which direction was the bone loaded? (3 pts) Given the loading scenario, what biomechanical action were the muscles performing at the time of fracture? (10 pts) What mechanical factors could have contributed to this failure? b. C. d.

Explanation / Answer

a) The knee joint is the weight bearing joint of the body . So if we know the Weight of the weightlifter and the total weight with the weight that he is lifting . We can calculate the force needed to cause the avulsion .

b )Bones are the strongest when the force is applied longitudnally or axially (compression and stretching )

But when the load is applied tangentially , the bone is weaker in handling that .

Also , while getting up the knee joint rotates to get fixed in a particular position , this will bring an extra rotational direction to the bones.

c) First when the weightlifter brings the weight up ,the muscle undergoes Dynamix contraction , which means there is the change in the length of the muscle .

We know that the quadriceps contract while getting up , so there is concentric contraction .

Once the weight has been lifted , the muscle undergoes isometric contraction. ,they do not change their length .

If the load is much more than the tensile strength of this muscles , it will lead to avulsion .

d) the mechanical factors that may affect -

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