One common form of musculoskeletal injury is tendon-related disorders like tennis elbow and Achilles tendonitis. Your tendon is the connector that transfers power from your muscle generators to your skeletal structure to create movement. Under normal circumstances, healthy tendons glide easily and smoothly as the muscles contract. When tendons are injured, they cause pain, especially during movement.
Tendon: Structure and Function
A tendon is a tough yet flexible band of fibrous connective tissue that connects your muscles to the bones. They are not to be confused with ligaments, which connects bone to bone.
When muscles contract the force generated by the muscle(s) is transmitted to the end of the bone through the tendon to produce movement.This enables you to bend your elbows, walk, run and move in many other ways. The elastic behaviour of the tendons also allow it to act like a spring, storing and releasing energy.For example, when you walk with your heel coming in contact with the ground, your Achilles tendon at the back of your heel stretches as your ankle dorsiflexes (toes pointing up), storing energy within the tendon. This is followed by your forefoot coming in contact with the ground and then pushing off the ground to propel your body forward. Energy is released from your Achilles tendon during plantarflexion (toes pointing down) and forefoot contact to enable you to push off from the ground. Image Source: Peak Performance
However, when the tendon is unable to glide smoothly due to various reasons such as acute traumatic injury or acute strain to the tendon, the tendon becomes inflammed and swollen, causing pain with movement. This inflammation of the tendon is known as “tendonitis”.
Tendons can also degenerate or wear out in the absence of inflammation as a result of overuse or age-related degenerative changes. When degeneration of the tendon occurs in the absence of inflammation, it is referred to as “tendinosis” or “tendinopathy”.
Common painful tendinopathies include patellar tendinopathy, Achilles tendinopathy, and rotator cuff tendinopathy. Tendinopathies are often associated with too rapid an increase in activity; for example, a runner increasing mileage and intensity too quickly. Another factor associated with tendinopathies is faulty biomechanics.
Less than Perfect Recovery
Although tendons undergo healing when injured, the healed tendons never regain the same mechanical properties as before. This is in large part due to the release of a group of chemicals called matrix metalloproteinases (MMPs) during the remodelling of the healing tendon. Certain MMPs are capable of degrading collagen fibrils (the main components of a tendon responsible for its tensile strength). When collagen fibrils become degraded, the tendon loses some of its tensile strength, and becomes weaker.
Hence, even with normal muscle use, it may cause further damage or prevent optimal healing of the already injured weaker tendon, predisposing the tendon to faster rate of degeneration.
The implication of this less than perfect healing process is to start healing your tendon before they are too severely damaged. The further the extent of the injury, the tendon has to 'travel' a longer healing journey and less likely to make it back to its previous state. But in reality, for some, this is not a option, particularly for performance athletes whose high-volume training regime exacerbates the tendon injury but whose sports requires that they maintain the physical peak form. This cuts down on the rest that they requires.