Free Radicals and Their Effect on Tendon Strength

There are many factors that influence the way our bodies respond to injury and illness, such as age, gender, activity level, genetic predisposition, medical history and diet. While all of these factors play an important role in the healing process, the one that has recently drawn widespread attention in the scientific community is diet.

It is becoming increasingly apparent that changes in the foods we eat can result in significant changes to the way the human body functions and repairs. It is well known that a healthy diet is the foundation for a healthy body; however recent investigations have begun to explore the possibility that awareness of including or excluding certain substances from our diet can have a direct effect on a variety of injury and healing processes.

This is relevant to musculoskeletal physiotherapy in relation to the repair of tissue following traumatic or overuse injuries. The concept of reducing pain or inflammation through dietary changes is exciting and some initial research has already been undertaken, with a massive scope for continuing investigation.

At this stage, research in this field is focused on increasing collagen bonding strength through lowering oxidative stress in the affected area. Oxidative stress is caused by the excessive proliferation of reactive oxygen species (ROS) or ‘free radicals’. Free radicals are released from phagocytes to attack invading particles such as pathogens. While they are essential for normal functioning, excess free radicals can cause several negative processes in the body, including the breakdown of important structural proteins known as proteoglycans.


Proteoglycans have a stabilising and bonding effect on collagen fibres. These collagen fibres make up all the tendons of the body, in addition to numerous other structures. High levels of proteoglycans within a tendon places the tendon at a lower risk of injury. To protect proteoglycans, the excessive production of free radicals can be controlled through moderating dietary intake. In one study of mature rats it was found that rats who were fed a diet lower in free radicals had significantly less tendon degeneration that those on a ‘normal’ diet. In humans, decreased proteoglycans is associated with higher incidence of tendon disease, such as rotator cuff tendinopathy.

Free radicals have also been indicated in symptomatic arthritic knee pain. A 2005 study observed significantly higher levels of free radicals in the synovial fluid of the knee in patients who presented with symptomatic arthritis. Patients who presented with asymptomatic arthritis of the knee were found to have much lower levels of free radicals in their synovial fluid. This indicated that free radicals may have a causative relationship to arthritic knee pain.

The application of nutritional supplementation and dietary control in the repair and prevention of musculoskeletal injuries opens up a plethora of research opportunities. Through maintaining a more comprehensive understanding, it is hoped that dietary management and nutritional supplementation will be able to assist in managing pain, reducing inflammation and promoting the efficient healing of injuries in the tendon and bone.

Lewis, J. S., & Sandford, F. M. (2009). Rotator Cuff Tendinopathy: Is There a Role for Polyunsaturated Fatty Acids and Antioxidants? Journal of Hand Therapy, 49-56.

Please comment below: