Tendon the Achilles tendon stretches as the ankle joint dorsiflexes. During the last portion of the stride, as the foot plantar-flexes (pointing the toes down), the stored elastic energy is released. Furthermore, because the tendon stretches, the muscle is able to function with less or even no change in length, allowing the muscle to generate greater force. The mechanical properties of the tendon are dependent on the collagen fiber diameter and orientation. The collagen fibrils are parallel to each other and closely packed, but show a wave-like appearance due to planar undulations, or crimps, on a scale of several micrometers. In
Quadriceps tendon rupture Quadriceps tendon rupture A quadriceps tendon rupture is a tear of the tendon that runs from the quadriceps muscle to the top of the knee cap. Symptoms are pain and the inability to extend the knee against resistance. A gap can often be palpated at the tendon's normal location. The diagnosis is usually made clinically, but ultrasound or MRI can be used if there is any doubt. The tendon can be surgically repaired. Afterwards a brace is given that prevents flexion of the knee. Athletes who have suffered this injury generally return to action in about 9 months to a