Do you know the difference between a sprain and a strain? If not, you may not know the difference between a ligament and a tendon. If you don’t know what those are, this blog might be a rollercoaster of information for you.

Oftentimes, the terms ligament and tendon are interchanged improperly. Some may even think their relationship is similar to that of the square and rectangle. Or, a mandarin and an orange. Fortunately, the relationship between a ligament and a tendon is straightforward.

Although similar, ligaments are not tendons. Tendons are not ligaments. Before we get into their differences, let’s discuss their similarities.

Connective Tissues Connecting Stuff

Ligaments and tendons are made out of soft collagenous tissue. Collagen is a structural protein. It makes connective tissues that connect things together. Skin is collagen based.

Ligaments and tendons can adapt to their mechanical environment. If you become injured, diseased, or exercise, ligaments and tendons will adjust their composition accordingly. They will stiffen or relax depending on the stimuli imposed on them.

They have a hierarchical structure, which is a weird word to say. This is much like a muscle. Muscles are broken down from the main muscle itself, into fibers, fibrils, and so on and so forth. Ligaments and tendons go from the tissue itself, which is made up of these smaller strands called fascicles.

These fascicles are made up of even smaller stands called fibrils. Imagine a stick of string cheese. You can pull it into big strands that break up the cheese into thirds. If you have a tiny mouth, you can pull apart finer strands for easier consumption. These fibrils are important. Their design is essential to understanding the difference between a ligament and a tendon. Also, if you want to understand how ligaments and tendons adapt to training, it’s good to understand how fibrils work.

You can see in this image that these fibrils make a wave-like pattern. This is called ‘crimping.’ Just like a muscle, ligaments and tendons can stretch. The first part of that stretch is when the waviness straightens. It does not take a lot of force to be able to uncrimp these fibrils. However, after that, the fibril itself becomes stretched. The stiffer the tissue, the more force it will take to stretch the fibrils. If too much stretching occurs, the tendon or ligament tears. A tear for a ligament is called a sprain. A tear for a tendon is called a strain. Strain has a ‘t’ in it. ‘T’ for tendon. Don’t say I never taught you nothin’.

As you can see from this graph, tissue lengthening happens in 3 phases. There is the toe region. This is where the uncrimping occurs. Then, there is the linear region. Here, the fibrils begin actually stretching. Then, there is the failure region. You can imagine what happens here. This is where the fibril tears. Effective training is designed at increasing the point where failure occurs.

When we add time as a variable, some more interesting things occur. Even when the load is constant (i.e. 225lbs on a barbell) the rate at which tissue deforms is not. This is called ‘creep.’ Tissue will continue to deform at an increased rate as time continues on. When you stretch, you don’t need to continue to increase the intensity of the stretch. Time is enough.

As time goes on and the tissue continues to deform, it will relax. elaxation of tissues is key to improving tissue length.

What’s The Difference Between a Ligament and Tendon?

Ligaments

The biggest difference between a ligament and a tendon is what they attach to. A ligament connects bones to other bones. Your anterior cruciate ligament, or ACL, connects your femur to your tibia. Your ACL is accompanied by a whole bunch of other ligaments of the knee to create stability. Also, they help stop your leg bones from separating from each other. Which is a nice feature.

Ligaments structure is also a bit different than a tendon. There are fewer of those fibrils I mentioned earlier. Also, they aren’t quite as organized. Their direction almost seems random. However, ligaments don’t just experience forces that pull in one direction. The forces that act upon ligaments can come from many directions. So, the nonlinear fiber direction makes more sense.

Ligaments are made up of more type 1 collagen versus type 3 collagen. Type 1 collagen is more resilient. Type 3 collagen is more elastic. That means that ligaments are more resistant to forces. This is good. You can imagine that you wouldn’t want a very stretchy ACL trying to hold your knee together.

This makeup allows it to do its job. Ligaments job first and foremost is to resist external load. If it does this job well, it will prevent excessive motion at the joint. This will also allow the joint to move properly. Ligaments help guide the motion of the joint surfaces.

Ligaments also have sensory receptors. These receptors are similar to the ones in muscles. They help ligaments understand its own length, stiffness, location, and orientation with respect to the bones it is attached to.

Tendons

Tendons connect muscles to bones. If we continue to think about the knee, the big pieces of connective tissue crossing your knee cap are tendons.

Unlike ligaments, the fibril direction of tendons is pretty straight. That is because the forces that they transmit come from the muscles they attach to. Generally speaking, these forces are mostly unidirectional.

Tendons are also primarily made of type 1 collagen fibers. Like ligaments, they need to be stiff. They are not like certain organs that need a lot of stretchiness.

So what do they do?

Tendons carry forces from muscles to bones. It may be easy to imagine that the tendons work like a pulley. They provide the muscle with more mechanical advantage to do its job effectively. Ligaments do not carry compressive forces (pushing down on it). However, tendons can accept these types of forces in instances, like the knee, where they wrap around the bone.

So, Why Should You Care?

You should care because these little pieces of connective tissue will be the bane of your existence if you mistreat them. How do I know? Because numerous studies show that tendon and ligament health severely decreases after a lack of use. This causes immobility, joint dysfunction, pain, and many other unfun things. However, much of that loss can be returned from properly prescribed exercise.

When you age, it becomes even more important that you treat your ligaments well. The properties of these connective tissues break down. This is further advanced by immobilization. So, get moving grandma!

But, How Should I Move?

When we discuss training, we have to bunch tendons and ligaments together. Although they are different, it is almost impossible to isolate a tendon or a ligament in training. However, for simplicity sake, let’s only discuss tendons.

I’ve talked a little bit about stiffness. It should be noted, however, that stiffer is not always better. This will be hard to judge, but you’re looking for muscles that are stronger than the tendons are stiff. That is not to say that really lax tendons is the goal.

A great example is the achilles tendon. Watch an elite sprinter. What you will notice is that their heels never touch the ground. That is partly because their achilles tendon is really stiff. Like a set of sports shocks in a car, the less movement the better. It should be noted that elite sprinters have really strong muscles. Like, really strong. So, they can handle the stiffness without their tendons tearing its insertion point off of the bone. Also, elite sprinters have very good ankle mobility. There is a balance to these things.

How do we find that balance? First, it will be important to determine how strong you are. If you are in Naples, Florida, I can find that out with you. Then, we need to find out how mobile you are. Getting an assessment by a fitness professional would be a good start.

If you need to increase mobility, slow loading of tendons is key. You might want to consider this path if you are weak and have limited flexibility. This goes back to the creep concept from earlier. The constant load for longer durations will help increase deformation (lengthening of tissue). Eccentrics and isometrics will do the job.

If you need to increase stiffness, faster loading will be best. Use this strategy if you are strong, mobile, and want tendons that cooperate. This can come from jumping, cutting, and sprinting. If you play sports, you’ll develop a lot of tendon stiffness just from your sport alone.

So there you go, another step closer until you know more than me about the human body!

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References

Dente, A. (2015, April 17). Structure and Function of Ligaments and Tendons. Retrieved October 15, 2020, from https://physiotherapymilan.it/paper/structure-and-function-of-ligaments-and-tendons-2604/

Structure and Function of Ligaments and Tendons. (n.d.). Retrieved October 15, 2020, from http://sites.bsyse.wsu.edu/pitts/be120/Handouts/animal%20tssue%20descriptions%20and%20mechanical%20proprties.htm

Tuura, J. (2019, April 17). 3 Concepts for Juicy Tendons. Retrieved October 15, 2020, from http://jackedathlete.com/3-concepts-for-juicy-tendons/