Ligaments are the specialized tissues that connect bones to other bones and ensure organs stay in place. Joints are the most place where ligaments attach, though they serve different purposes as well. Collagen fibers bundle parallel to each other to form bands of dense regular connective tissue. These bands form ligaments and tendons. Because dense regular connective tissue has a poor blood supply, when these areas are injured, they are slow to heal. However, they are also difficult to damage due to their high tensile strength.
The main purpose of most is to passively stabilize whichever joint they span. They help guide the joints through an appropriate range of motion and protect the joint from overextending. The ligaments are also partially responsible for proprioception, the body’s innate ability to sense the position of each body part, as well as the strength used to move them. Without proprioception, it would be incredibly difficult to perform many tasks, such as bringing food to the mouth or brushing hair. The ligaments provide this sense by creating neurological signals when strained.
Many connective tissues in the body are similar to each other. Ligaments connect bones to bones, while tendons connect bones to muscle. Fasciae are the tissues that connect muscles to other muscles, though they occasionally connect to other structures as well. Tendons typically have more elastic tissue than ligaments, allowing for increased range of movement. Fasciae are even more flexible than tendons. For example, the skin has a layer of fasciae that allows it to stretch and shrink along with changes in weight.
The body has many different types that are classified depending on their location and band shape. Peritoneal ligaments are folds of smooth tissue membrane that connect organs such as the stomach and spleen. Periodontal ligaments connect the teeth to their surrounding jaw bone. Articular ligaments are the normal ligaments that connect bones, but they are classified even further based on their structure. For example, the knees have two different types of articular ligaments: cruciate and collateral.
Paired ligaments shaped like the letter X are cruciate or cruciform ligaments. The most well known cruciate ligaments in the human body are the anterior cruciate ligament and the posterior cruciate ligament, known by most people as the ACL and PCL, respectively. The X shape allows the crossed ligaments to provide additional stability while maintaining an impressive range of motion. Collateral ligaments are located on the sides of the knees. They protect the joints from varus and valgus deformities that affect the direction and freedom of a joint’s movement.
Ligaments with collagen defects or that connect to abnormally shaped bone ends are the most common causes of hypermobility. Around ten to 25% of the population has hypermobility, though most people know it as double-jointedness. For most people with hypermobility, there are no negative side effects or symptoms. However, some individuals develop joint hypermobility syndrome, which can lead to significant pain, fatigue, and easily dislocated joints. Though there is no cure, physical therapy and lifestyle modifications can help alleviate the more problematic symptoms.
When a joint separates abnormally, it is a dislocation or luxation. Usually, some form of trauma, such as a fall or impact, is responsible for a dislocation. The shoulder is the most commonly dislocated joint, though athletes often suffer ankle and knee dislocations as well. The nerves, ligaments, muscles, and tendons are all vulnerable to damage during a dislocation. Additionally, if a medical expert does not treat a dislocation quickly, the ligaments can become stretched and weak, leading to a greater likelihood of future dislocations.
Beyond dislocation, many people injure the actual ligaments of a joint. For example, over 100,000 people in the US every year suffer torn ACLs. Sudden changes in motion such as pivoting are responsible for most ACL tears. This rotation places more strain on them, causing them to snap. Experts categorize ligament injuries into three grades based on severity. Intense and sudden pain accompanies such injuries, as well as severe swelling.
Because they lack the blood supply necessary to heal, they usually do not regenerate on their own. Instead, the ligament must undergo reconstructive surgery. Though doctors can perform various surgeries, the most common is to replace the ligament with artificial material. Some surgeons choose to replace the ligament with a piece of healthy tendon from a donor or somewhere else in the body. The surgeon grafts the healthy tendon into place, and it acts similarly to a ligament.
Thankfully, due to their strength and elastic nature, ligaments are quite difficult to damage. The best way to prevent damage to the ligaments is to ensure the muscles surrounding the joint are strong. For example, people can avoid ACL tears by strengthening the hamstrings in the back of the thighs and the quadriceps in the front. If a pivot is necessary, turning at the hips as well as the knees can reduce the stress on the joint. Advice is similar for the rest of the body. Avoiding a ligament tear in the shoulder requires back and arm exercises.
The vast majority of people experience successful reconstructive surgery on their ligament tears. A torn ligament will require months of exercise and physical therapy to ensure the muscles surrounding the joint remain strong enough to prevent further injury. Upwards of 80% of athletes that experience a ligament injury can return to their sport within a year. However, depending on the severity of the tear and age of the person, doctors may restrict exercise and movements to pivot-less options. Additionally, there is a high chance for a repeat injury following a torn ligament.
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