Tendons are tough but flexible connective tissues that attach muscles of the body to bones. When a muscle contracts, or shortens, it is the corresponding tendon that pulls on the bone of the muscle attachment to create movement. In other words, the tendon is the structure that transmits the force of the contraction to the bone. Due to the thickness of its fibrous tissue, a tendon provides joint stability at the articulation, the meeting, of two bones. Depending upon the location in the body, a tendon can be involved in the flexion, flexor tendon, or the extension, extensor tendon, of a body part.
Achilles Tendon
The calcaneal tendon, commonly referred to as the Achilles tendon, is the strongest tendon in the body. It is the insertion point of the superficial, or outermost, posterior muscles of the lower leg. The point of insertion is at the calcaneus, more commonly known as the heel bone. A rupture, which is a complete tear, of the Achilles tendon requires surgical repair. Complete rehabilitation can take up to a year.
Patellar tendon
The patellar tendon is located at the knee joint. Actually, it is a continuation of the powerful quadriceps tendon. It crosses over the patellla bone, referred to as the knee-cap, and attaches to the tibia of the lower leg. It is paramount to the stability of the knee joint, which is the most unstable joint in the body. Pulling of the quadriceps muscle on the patellar tendon results in knee extension.
Tendons of the hands and feet
Fingers and toes have extensor tendons on top and flexor tendons on the bottom. Pulling on the bones to make a fist or to curl the toes is done by the flexor tendons. Conversely, unclenching a fist or extending the toes is a job for the extensors. In normal situations, extensors are visible through the skin in hands and feet. Boutonniere deformity, named for its buttonhole appearance, is an injury to the the extensor tendon in the finger. It is the result of a jammed finger or trauma to the finger. In this instance, the finger is frozen in a bent position as the extensor is unable to straighten it.
Tendons of the elbow
Elbow flexion, or bending, is a result of the biceps muscle of the upper arm pulling on its tendon, which is attached across the elbow joint to the forearm. The corresponding triceps muscle, which is located on the opposite of the humerus bone and attaches to the forearm, then extends or returns the elbow to a straightened position. Tendonitis, an inflammation of the tendon, is a common injury or source of pain in the elbow regions. It is usually the result of overuse. Tendonitis on the medial aspect (closer to the midline of the body) is known as golfer's elbow. The more frequent occurrence of inflammation happens to the lateral aspect (away from the midline of the body) and is known as tennis elbow.
References
- "Introduction to Sports Medicine and Athletic Training," Robert C. France; 2004.
- "Principles of Anatomy and Physiology," Gerard J. Tortora and Bryan Derrickson; 2009.
