What are Tendons?

Shannon Kietzman

Tendons, or sinews, connect muscle to bone. The bones in a person's skeleton enable him or her to walk, run, jump, roll, lift, carry, drop, and do other important physical activities. Without the connection between the muscles and bones that are responsible for controlling these actions, it would be impossible for the body to move in the way it does. Since tendons are important for body movements, it is important to keep them strong, healthy, and free from harm.

A model of a human hand with the tendons shown in red.
A model of a human hand with the tendons shown in red.

The composition of tendons is much like gelatin, but harder and not as elastic. They are made of special cells called tenocytes, water, and fibrous collagen proteins. Millions of these collagen proteins weave together to form the strong strand of flexible tissue. Tendons grow into the bone and form a tough mineralized connection. This connection creates a permanent bond that is extremely tough to break.

This diagram shows some common problems with the Achilles tendon.
This diagram shows some common problems with the Achilles tendon.

Despite their incredible strength, tendons can be damaged if overstrained or improperly cared for. Overuse can cause the collagen fibers to form small tears, a condition called tendinitis. Damage most often occurs in the knee, ankle, shoulder, wrist, bicep, calf, and back of the heel, which is called the Achilles tendon. This tendon is named after the mythological figure, Achilles, who was killed when an arrow struck him in the back of his heel. The Achilles tendon connects the heel to the back of the calf, and since it is used so frequently, it is one of the most commonly damaged.

Tendons in the bicep are more susceptible to damage.
Tendons in the bicep are more susceptible to damage.

Tendons cannot easily heal from damage, which makes medical intervention necessary when one is injured. If they are damaged, anti-inflammatory drugs are used to bring the swelling down. Complete rest for a long period of time is generally mandatory. If one tears completely, surgical intervention is necessary to reconnect the tissue to the bone.

Tendon injuries can be very painful, and often require physical therapy or other medical intervention to repair.
Tendon injuries can be very painful, and often require physical therapy or other medical intervention to repair.

Strength training can help ensure that the tendons remain tough and less susceptible to damage. As a person ages, this tissue also ages, and excess weight and activity can slowly weaken them over time.

A tendon connects muscle to bone.
A tendon connects muscle to bone.

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Discussion Comments


@anon72391 - It doesn't sound to me like you have damage to the hip tendons (although I'm not a doctor). It sounds more like you've got arthritis or some other kind of inflammatory disease.

If you haven't already gone to the doctor and had it checked out, you really need to do so. Getting arthritis at your age isn't normal and you need to get on the right diet and medication and exercise regime to try and halt the spread of whatever it is in its tracks.

Good luck, I do hope you feel better.


@anon41194 - That's just where your tendons are put under the most stress. They are also more exposed there.

You are more likely to get hit in the elbow or to fall on your knees just because those parts stick out further most of the time. Likewise, you'll probably twist an ankle sooner than you'd twist the tendons in your calve, because the ankle is supposed to twist a little anyway.


@Bop66 - Personally, I would not let him play until it is healed. I'm not an expert and you should definitely get a medical opinion on this, but I've known friends who have damaged their ligaments and often if they don't take it easy they end up with more damage.

Ligaments take a while to heal because they don't have the same blood supply that muscles and other areas do. Which is why they often don't hurt as much either, making you think perhaps it's OK to push a little bit. But it's like driving with a flat tire. Possible, of course, but you'll end up wrecking the tire completely and possibly damaging the car as well.

Just make him be patient and find another hobby until he's completely healed up. Unless he's got the medical support that the pros do (and even they don't play with torn ligaments if they can help it) rest is what he needs.


I hurt my wrist really badly and have sprained it. Does anyone know how long it takes to heal?


I completely tore my pectoral tendon from the muscle. can it be reattached with reconstruction?


my father, age 56 years had a tear of the achilles

tendon and had surgery for it by grafting. it took place two months back. It is now nearly june and the dr is going to remove the cement slab. what care is to be taken and what makes tendon formation quick? can he keep the leg down and walk? please send me a reply. Thank you.


i am a 33 year old man. i have the problem that my hip is (inside) swelling. It started hurting eight years ago. First I had the pain two or three times a week. Now I'm paining every second and swollen please may i know what is the treatment for this. thanks.


can i run or walk briskly if my tendons are replaced? Please help.


why do tendons normally damage where there is always a joint, such as ankles, knees, elbow?


whats an ulnar ligament?


Hi, My son is 17 and has torn his Ulnar ligament in elbow. I am wondering if anyone knows how long this takes to heal or if with a good hinged brace it offers enough protection that he can play football? Should he not play until completely healed.

Thank you,

Worried Mom


What destroys the mineralization connection at the end of the tendons that grow INTO your bone?

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