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
Patellar tendon rupture Patellar tendon rupture Patellar tendon rupture is a tear of the tendon that connects the knee cap (patella) to the tibia. Often there is sudden onset of pain and walking is difficult. In a complete rupture the ability to extend that knee is decreased. A pop may be felt when it occurs. Injury to the patellar tendon generally requires a significant force such as falling directly on the knee or jumping from a height. Risk factors include patellar tendinitis, kidney failure, diabetes, and steroid or fluoroquinolone use. There are two main types of ruptures partial and complete. In most cases,