We may experience back pain due to tendonitis of the tendons that connect the back muscles or abdominal muscles to the spine, or the rupture of tendons due to trauma or injury.

The tendons and other soft tissues support the muscles and joints to provide for movement and stability to the moving parts of the body, including the spine. The tendons are found on the end of muscles, and connect muscle to bone. The bones move or rotate in one direction when the muscles are flexed (contracted), and in the opposite direction when the same muscles relax. Like the ligaments that connect bone to bone, the tendons are connective tissues built for strength but also flexibility. Tendons are among the soft tissues of the spine and musculoskeletal system, and their makeup includes layers of collagen (fibrous connective tissue). The tendons are capable of withstanding tension, as is required nearing weight bearing joints such as the shoulder and heel. The ends of tendons and muscles are connected, and they move together as the muscles and joints move.

In most regions of the musculoskeletal system, the tendons are composed of closely packed bands of collagen fibers that run parallel to one another. These percentage composition of these fibers are approximately 70% water and 30% of solid material. Of this solid material, about 86% is composed of collagen, followed by 2% elastin, 1-5% proteoglycans, and 0.2% trace elements including calcium, manganese, and copper.

Physiology and Function: Until recently, the tendons were considered passive structures whose job was simply to unit muscle to bone, and to pull the bone in the direction that the muscle wanted it to go. In other words, the tendon's function was simply to transmit force. However, closer study of body mechanics and kinesthesiology indicate that the elastic properties of the tendons enable them to act as springs. These abilities to act as springs enable them to build and store energy when they are not transmitting forces, and to release energy at the moment when the tendons is being used as a spring. The passive and active mechanical abilities of the tendon allow our bodies to produce powerful movements or thrusts when performing explosive movements such as jumping, throwing, and swinging a hand-held object.

An example of the passive and active use of the tendons during locomotion is the Achilles tendon, which connects between the heel and the calf muscles of our lower leg (soleus and gastrocnemius muscles). During a single stride, there is a dorsiflexion of the ankle joint (turns towards the shin) as the Achilles tendon stretches (elongates). There is a buildup of potential energy as the Achilles tendon stretches. During the end of the stride, the ankle joint plantar-flexes as the foot pushes off the ground. It is during this portion of the stride that this potential energy in the tendon is converted to kinetic energy, and the tendon aids the muscles in pushing the leg off the ground. Also, the ability of the tendon to stretch with no change in the muscle's length allows the lower leg muscles to generate greater force.

Though the tendons are built to withstand stretching and a large amount of tension being applied to them, they are prone to injury like any other joint, muscle, or soft tissue. Due to injury or repetitive stress, the tendon may become inflamed and irritated. This tendon condition is known as tendonitis. Tendonitis may occur due to overuse or deficiencies in blood supply to the tendon while it is in heavy use.

We may experience back pain due to tendonitis of the tendons that connect the back muscles or abdominal muscles to the spine, or the rupture of tendons due to trauma or injury.