Well remember that the musleoves the bone one way and that one way is the bent
Muscles, bones and tendons work together to move your arm. The tendons will connect the muscles to the bones and the bones will provide the necessary support which will facilitate the movement.
Muscles change the relative position of the bones. The bones are just the passive (but required) part.
The bones do not move, neither do they work alone. In order to move the bones need help from the joints and muscles. The muscles pull on the joints therefore making the bones move.
The bones and muscles of the leg work together when the leg moves. The bones give the leg its structure, while the muscles hang onto the bones and allow the leg to actually move. The muscles make their movements via contractions and expansions.
Your muscles pull on bones but they never push bones.
Long bones.
The muscles used to straighten the leg are commonly known as the Quadriceps, a group of four muscles on the front of the thigh. This, however, is only the cast when the knee is isolated. If you were to stand up from a squatted position, you would also be using your gluteal muscles as well as your hamstrings to extend the thigh and stabilize the knee, while your quads and inner thigh muscles (the adductor) help to straighten the the knee. You would also be using your calf muscles to straighten the ankle.
The muscle that causes a joint to straighten when it contracts are the extensor muscles. These include the triceps that work with the biceps to extend the arm.
The Muscles are attached to the bone through Tendon. All the body movement from the brain goes to the muscles and muscle in turn transmit to the bones.
The biceps flexes the arm it does not extend it (straightens). The triceps brachii extends the arm. They do work together. If one is damaged and doesn't work as it should, the movement will be "jerky" and not smooth.
Ligaments
Movement