Ligaments are thick fibrous bands of tissue that connect bone to bone and provide stability to the joints of the body. Unlike muscle tissue, ligaments do not have contractile properties and cannot voluntarily shorten or lengthen at will. Ligaments are viscoelastic structures. This means that when placed under load the ligament will stretch and return to its normal resting length once the load is removed. However in cases where the load is excessive a ligament will fail or tear.

Unfortunately ligaments do not heal in the same way as muscle, when a ligament tears there will be localised bleeding, the blood will bring repair cells to the injured site and these cells will start to lay down new fibers between the two ends of the tear. These new fibers will grow and in most cases eventually knit together with the two ends of the torn ligament. Although the ligament is now one again it is no longer the same length as it was prior to the injury and is lengthened and more lax. This laxity in the ligament post injury is what causes the joint to become unstable increasing the likelihood of further injury. In certain cases where there is complete rupture of the ligament a surgical repair may be required to return full functional stability to the joint in question. A common example of this is the anterior cruciate ligament of the knee. Other common sites for ligament injuries include the ankle, shoulder and wrist.