The muscles, bones, ligaments and tendons all work together in response to signals from the brain. Tendons are strong bands of connective tissue which connect muscles to bones and their job is to help the muscles move the joint. Ligaments, on the other hand, connect one bone to another and help to stabilize the joints by limiting how far they move, this helps protect against injury.
A good example of a tendon Is the illiotibial band (ITB) which runs from the outer edge of the thigh down to the knee where it attaches to the tibia. Problems can occur, especially for runners who run on uneven surfaces or do a lot of hills, or when the hip muscles are weak. The tendon may become tight and inflamed and it can often be felt as soreness and pain on the outside of the knee which feels worse going downhill or down stairs. In my experience women appear more prone to suffer pain from this than men.
When I treat someone with this problem I focus on the hip abductor muscle just above the ITB as this has often become tight and working on this can take the pressure off the ITB. Any work done over the ITB itself has to be done with care as tendons aren’t designed to stretch much and it is close to the bone underneath, too much pressure can be very painful. Gentle lifting and stretching the tendon is very effective. Similarly with foam rollering, if you want to roll out the ITB that’s fine but just don’t be heavy handed with it or it won’t thank you afterwards, I speak from bitter experience!