The Anatomy of Ligaments

Ligaments are tough, fibrous connective tissue that connect two adjacent bones and help to keep them stabilized within a joint space. The main job of ligaments is to provide stability to joints and bones throughout the body. In fact, the function of ligaments are reflected in their name, which comes from “ligare”—the Latin word for “bind” or “tie.” When you suffer a ligament injury, you lose stability at the injured site.

Anatomy

Ligaments appear as crisscross bands that attach bone to bone and help stabilize joints.

Structure

The basic building blocks of a ligament are collagen fibers. There are approximately 900 ligaments throughout the body that are composed of dense bundles of collagenous fibers. These bundles are surrounded by a gel-like substance called ground substance. They vary in size, shape, orientation, and location.

Collagen is strong, flexible, and resistant to damage from pulling or compressing stresses. This allows the ligament to withstand a wide range of forces during movement. Collagen fibers are arranged within parallel bundles to multiply the strength of the individual fibers. 

The bundles of collagen that make up most ligaments attach to an outer covering that surrounds all bones called the periosteum. At this attachment site, there may also be an additional lubricating membrane, the synovial membrane, and pouch. Together this forms a bursa sac, which provides a cushion for and nutrients to the surrounding bone.

Location

Ligaments are found throughout the body. Some help connect bones at joints, while others help to stabilize two parts of the body and restrict movement between the two, like the ligaments of the womb which keep it in the right position in the pelvis or the ligaments in the bones and forearms that keep them from pulling apart.

Most ligaments are contained around moveable joints, which include:

• Ankles
• Knees
• Hips
• Elbows
• Shoulders
• Back
• Neck
• Fingers

But some are contained around immovable bones like ribs and the bones that make up the forearm.

Function

Ligaments attach bones to other bones, especially at the joints and allow you to move freely, easily, and without pain. Most ligaments run at different angles to the bone and muscles that they support and provide stability throughout the joints full range of motion.

Types of Ligaments

Ligaments differ based on the anatomical structure they support. Some are stretchy while others are sturdy. No matter the case, ligaments provide stability to organs and bones throughout the body and are integral to maximal range of motion, smooth movements and pain-free mobility.

Knee Ligaments

• Anterior cruciate ligament (ACL): Arises from the posterior lateral portion of the femur and attaches at the medial anterior portion of the tibia, and controls twisting motions and forward movement.
• Posterior cruciate ligament (PCL): Runs from the front area of the femur and around to the back of the tibia. It prevents backward movement of the tibia in regards to the femur.
• Medial cruciate ligament (MCL): Attaches to the interior part of the tibia and primarily prevents valgus stress (excessive outward movement) and stabilizes against twisting of the leg. 
• Lateral collateral ligament (LCL): Attaches to the outer portion of the tibia and fibula and prevents varus stress (excessive inward movement) and also helps stabilize against twisting. 

Elbow Ligaments

The two ligaments of the elbow are the:

• Ulnar-collateral ligament: Also called the medial collateral ligament, which runs along the inside of the elbow.
• Lateral collateral ligament: Also called the radial collateral ligament, which runs along the outside of the elbow.

These two ligaments work together not only to help stabilize the elbow joint but to also allow you to flex and extend your arm. 

Shoulder Ligaments

There are five major shoulder ligaments that keep the shoulder in place and prevent it from dislocating. The five ligaments are contained within the glenohumeral and acromioclavicular joint spaces of the shoulder.

• Superior glenohumeral ligament
• Middle glenohumeral ligament
• Inferior glenohumeral ligaments 
• Acromioclavicular ligament
• The coracoclavicular ligaments 

The glenohumeral ligaments help to stabilize the glenohumeral joint which connects the shoulder socket, or glenoid, to the arm bone, or humerus. The glenohumeral ligaments help us to extend our arm from the shoulder blade.

The acromioclavicular (AC) joint, which is plane joint that connects the upper part of the shoulder blade to the collarbone, or clavicle, and allows for three degrees of freedom, or more simply allows the upper arm to glide in multiple directions. This flexibility also makes the shoulder more prone to injury.

Ankle Ligaments

If you have ever twisted or sprained your ankle, you probably injured your anterior talofibular ligament. This is one of three ligaments that make up the lateral collateral ligament complex (LCL) on the outer portion of the ankle. The other two ligaments are the calcaneofibular and the posterior talofibular ligaments. These ligaments can be damaged if you have a severe sprain or ankle fracture.

The medial collateral ligaments (MCL), also known as the deltoid ligament, are located on the inside portion of the ankle. This group of ligaments is divided into a superficial and deep group of fibers. The MCL is covered by tendons that shield it from trauma and injury. 

Hip Ligaments

The hip contains four major ligaments and is divided into outer capsular ligaments and inner-capsular ligaments. They both assist in the flexion and extension of the hip.

The three capsular ligaments include:

• Iliofemoral ligament (Y ligament of Bigelow): The strongest ligament in the body and attaches the anterior inferior iliac spine (AIIS) to the intertrochanteric crest of the femur.
• Pubofemoral ligaments: The pubofemoral ligament prevents excess abduction and extension of the hip. 
• Ischiofemoral ligaments: The iliofemoral prevents hyperextension of the hip.

The sole intracapsular ligament is the ligamentum teres (ligament of the head of the femur) that serves as a carrier for the foveal artery, a major blood supply source in babies and young children.

Back Ligaments

There are 7 ligaments that support the spine:

• Ligamentum flavum: Located in between the vertebrae
• Facet capsular ligament: Located at the capsular insertion point along the sides of the spine
• Interspinous ligament: Located in between the spinous processes
• Supraspinous ligament: Located above and to the side of each vertebra
• Intertransverse ligament: Located in between the long pointy sides of each vertebra
• Posterior longitudinal ligaments: A long, thin ligament that runs along the backside of the spine
• Anterior longitudinal ligaments: A wide, fibrous band that runs along the front of the spine

The posterior and anterior longitudinal ligaments are the major contributors to the spine’s stability. Injury to the posterior longitudinal ligament can result in disc herniation, which may render you unable to flex backward without pain. If your back goes out, especially if you suddenly hyperflex or twist your back, you may have injured one or more of these back ligaments.

If you have ever had back pain, you know how painful and debilitating it can be. In fact, back pain due to ligament sprains and strains are one of the leading causes of back pain in the world.

Ligament Injuries

Injury to a ligament results in a drastic change in its structure and physiology and creates a situation where ligament function is restored by the formation of scar tissue that is biologically and biomechanically inferior to the tissue it replaces.

Some of the most common ligament injuries include:

Anterior Cruciate Ligament Tears

An ACL tear is by far the most common knee injury and ligament tear that you may hear about. It commonly occurs, up to 80% of the time, as a result of a contact sports injury. During an ACL tear, you may hear a pop and feel immediate instability in the knee. The knee is a highly vascularized area so rupture of the ACL leads to rapid inflammation due to blood pouring into the knee space causing a hemarthrosis. Most of the pain felt during an ACL tear is due to inflammation.

An ACL tear was once thought to be a career-ending knee injury for an athlete, but that is no longer the case due to many surgical advances. An ACL tear can lead to:

• Altered movement
• Muscle weakness
• Reduced functional performance

It may lead to the loss of an entire season or lack of sports participation among young athletes.

It is also associated with long-term clinical sequelae including:

• Meniscal tears
• Chondral lesions
• Increased risk of early-onset post-traumatic osteoarthritis

Fortunately, early surgical treatment lessens the risk of long-term sequelae.

Knee sprain

Leg injuries are very common in sports. Fortunately, these injuries most oftentimes are a knee sprain or injury to the medial collateral or lateral collateral ligament of the knee. A knee sprain may feel like buckling of the knee and it may be accompanied by pain, swelling, and weakness in the leg.

Elbow Sprain

The most common injury to the elbow ligaments is the rupture of the medial collateral ligament. This often happens to athletes who repeatedly throw overhead, such as baseball pitchers, javelin throwers, quarterbacks, tennis, volleyball, and water polo players.

The inside twisting motion on the elbow during the late cocking and early acceleration phases of the movement causes excessive strain on the ligament leading to rupture. The initial presenting sign may be instability of the elbow, although the clinical presentation may vary. You may also feel pain at the elbow joint and experience reduced accuracy and decreased velocity with the affected arm. A significant rupture requires surgical repair. 

Hip Dislocation

Hip dislocations can occur in children and adults. Injuries to the ligamentum teres can result in a dislocation after a traumatic fall and are especially alarming in children. While the vascular contribution of the foveal artery that is housed by the ligamentum teres is small in adults, it can result in osteonecrosis or death of the femoral head in children. 

Hip dislocations are less common in adults. Most hip injuries are strains or sprains caused by car accidents, trauma directly to the hip, or other more subtle causes such as overstretching the muscles and ligaments in the hip, insufficient warm-up prior to rigorous physical activity, and ramping up activity after sustaining a soft tissue injury.

Ankle sprain

The ankle sprain is one of the most common sports-related injuries, especially in basketball. Pain, swelling, and difficulty moving the ankle may ensue. Initiating the R.I.C.E protocol—which consists of rest, ice, compression, and elevation—has been shown to help reduce swelling and improve the time of recovery.

Other treatments include:

• Use of anti-inflammatory medication like ibuprofen
• Use of crutches
• Use of splint or cast
• Physical therapy

Spinal Ligament Injuries

Spinal ligament injuries most commonly occur after traumatic events like a a car accident. Common causes of spinal ligament injuries include:

• Back ligament sprain (due to excessive twisting)
• Whiplash
• Text neck

Shoulder Ligament Injuries

The three most common shoulder ligament injuries are:

• Shoulder dislocation
• AC joint injury
• Rotator cuff tear

Spraining the ligaments of the AC joint often happens when we fall on an outstretched hand. Trauma to the shoulder, a rotator cuff tear, and dislocation of the shoulder are also common injuries that may damage the AC and glenohumeral joint spaces and the ligaments that support them. 

The most common of the three are rotator cuff injuries and while it may happen as a result of a traumatic event, more commonly it develops from wear and tear as you age. Symptoms include:

• Recurrent pain with activities
• Shoulder pain that wakes up at night
• Limited range of arm motion
• Muscle weakness
• Cracking sounds in the arm or shoulder

A Word From Verywell

Ligaments are very important structures to the body, but oftentimes you aren’t aware of the role they play until you suffer an injury. Stretching before exercise and maintaining a healthy weight are two ways to help avoid ligament injuries.

Most ligament injuries can get better on their own or with conservative management like rest, ice, and the use of ibuprofen. If you think you have a ligament sprain or strain, be sure to contact a healthcare professional if the pain is unbearable or there is a visible deformity of the affected area.