1 The Injury
2 The Repair Process >
Ligaments link bones to other bones and provide support to joints. They allow a normal range of movement to occur within a joint, but prevent unwanted movement that would render the joint unstable. In order to fulfill this function ligaments must possess immense mechanical tensile strength. Ligaments are classified as dense connective tissue, and they consist of a protein substance called collagen. The organisation of collagen fibres gives the ligament its tensile strength.
Another function of ligaments is to provide proprioceptive input to the brain that allows a person to know what position the joints are in, without having to look. This helps to perform the complex coordinated activities needed for sport.
A normal ligament consists of:
Type 1 collagen is mature collagen tissue and has the greatest tensile strength. Type 3 collagen is immature collagen tissue and does not provide a great deal of tensile strength to the ligament. After being laid down by fibroblast cells it takes approximately three months for Type 3 collagen to mature into Type 1 collagen. As with other cells in the body, this process of renewal occurs continually.
When ligament tissue is examined under the microscope (see diagram) it can be clearly observed that the collagen fibres are arranged in a longitudinal pattern to resist the stress that is placed upon the ligament. The arrangement of the collagen fibres means that a great deal of force is required to damage ligaments. In a collision sport like football this force is generated by opposition players or when a player catches his foot in the turf and his whole body weight goes over one joint. This force produces structural damage to the joint capsule and ligaments, which is known as a ligament sprain.
Ligament sprains are classified as follows: