Tendinitis, Tendinosis, Tendinopathy – Do you know the difference?

In the UK the average Anatomy & Physiology course contains little information about tendons beyond that “they attach muscle to bone”, as opposed to ligaments which “attach bone to bone”. Sound familiar? When learning how to massage the emphasis is on origin and insertion with treatment being focussed on the muscle belly. If you have trained or are training in remedial or sports massage then you will have studied some pathologies associated with tendons, but treatment protocols will largely consist of conservative management techniques for inflamed tissue. After all that’s what it says in the majority of text books; however, it would seem little has been done to stay up-to-date with current research and practices developed largely in physiotherapy. This article therefore aims to explore how to select techniques that will be effective in resolving issues with tendons based on science, research and practical experience.

Anatomy of a Tendon

Before discussing pathologies, it is important to understand the structure of a tendon. According to Kanus (2000), tendons consist of collagen (mostly type I collagen) and elastin embedded in a proteoglycan-water matrix with collagen accounting for 65-80% and elastin approximately 1-2% of the dry mass of the tendon.

Collagen

The organisation of collagen is not dissimilar to that of muscle tissue in that collagen aggregates into microfibrils and then into fibrils which form a collagen fibre, the basic unit of a tendon. Each collagen fibre is surrounded by a sheath of connective tissue called endotenon which binds fibres together. A bunch of collagen fibres forms a primary fibre bundle, and a group of primary fibre bundles forms a secondary fibre bundle. A group of secondary fibre bundles, in turn, forms a tertiary bundle, and the tertiary bundles make up the tendon. The entire tendon is surrounded by a fine connective tissue sheath called epitenon.

The function of a tendon

Kanus explains that the complex structure of the tendon is important in preventing damage. Within one collagen fibre, the fibrils lie in three directions; longitudinal, transverse and horizontal. Some of the longitudinal fibres cross each other forming spirals. Similarly, some of the fibrils form spiral-type plaits. The basic function of the tendon is to transmit the force created by the muscle to the bone, and, in this way, make joint movement possible. During various phases of movements, the tendons are exposed not only to longitudinal but also to transversal and rotational forces. In addition, they must be prepared to withstand direct contusions and pressures. The three-dimensional internal structure of the fibres thereby forms a buffer medium against forces of various directions.

So what is the difference between tendinitis, tendinosis and tendinopathy?