Ligaments are one of those problematic body parts that people often confuse for something else, such as tendons. This may be because both ligaments and tendons are connective tissues, but whereas tendons connect muscles to bone, ligaments are what join one bone to another at our joints, allowing us to move, and also provide support by stabilising and sometimes enclosing a joint to make sure that each joint can only move through a safe range of movement.
The structure of ligaments allows them to perform their role whilst still providing maximum mobility. Essentially, ligaments are something like a stiff elastic band, made out of the protein collagen. Some ligaments are stiffer than others, as they have to maintain a joint in its set position and prevent a bone from moving around or against another in a way that it isn’t supposed to. An example of this would be the elbow joint, which can’t be bent backwards towards the triceps, but can move freely in a forward range of motion. At the same time, the ligaments prevent the twisting of the elbow joint, fixing the plain of movement in a straight direction, with no side to side or rotational movement possible.
These supportive ligaments, known as articular ligaments as they control the articulation or movement of the joints, are generally composed of strong, white and fibrous collagen. A number of ligaments usually criss-cross each other within our joints to provide the maximum support. These ligaments aren’t designed to stretch to any large extent, as being stretched will weaken their ability to allow the joint to move in a correct manner, without moving too far. Whilst ligaments always stretch a little, they are designed to return to the shortened position when no longer being moved.
If ligaments are stretched too far or over a prolonged period of time, they can assume the stretched shape permanently, rather than returning to their original shape when the joint is no longer moving. Such stiffening of the ligaments can lead to a very lengthy healing process. For this reason, ligaments should never need to be stretched in order to create flexibility, as stretching the muscles is what leads to flexibility. Also, dislocations of a joint should be set as soon as is possible, as a dislocation stretches the ligaments outside of their usual range.
There are also more flexible ligaments which are designed to stretch within a given range, much like an elastic band. These ligaments are generally composed of collagen more yellow in colour, and occur where movement of a varying degree is required, such as in the voice box, where the cartilage making up the voice box or larynx needs to be able to move to produce different sounds.
Some ligaments are there just to provide support, enclosing a joint, for example. This is true of the shoulder joint, where there is a ligament called the coracoacromial ligament. This ligament literally sits in position between the front and rear portions of the shoulder blade bone, or scapula, from the coracoid process which sits in the front of the shoulder beneath the shoulder-side of the collar bone, and the acromion, which forms the upper part of the shoulder blade in the back. The ligament sits between the gap that exists between these two parts of the same bone, literally acting like a roof over the arm bone, or humerus, which sits underneath the shoulder blade at this point. As the ligament is slightly flexible, we are able to lift and rotate our arms in the shoulder joint with the greatest freedom of movement, whilst the humerus is kept secured in the shoulder joint by this ligament.
So, ligaments are the connections which hold our bones together, allowing our rigid skeleton to provide support to our bodies, whilst also allowing us to move. They keep our joints moving in the way that they are supposed to, and no further, essentially acting as guards to our joints, keeping our bones in line.
(1998) The Hutchinson Encyclopedia, Helicon Publishing Ltd.