Tendon vs Ligament: What Is the Difference?
The easy way to remember it: tendons join muscle to bone, and ligaments join bone to bone. Tendons pass on the pull of a muscle so a bone moves. Ligaments hold a joint together so the bones do not move too far.
Tendon vs ligament at a glance
| Tendon | Ligament | |
|---|---|---|
| Size | The Achilles, the biggest, is about 15 cm long | The ACL in the knee is about 3 to 4 cm long |
| Joins | Muscle to bone | Bone to bone |
| Job | Passes on the pull of a muscle to move a bone | Holds a joint together and stops it moving too far |
| Made of | Tightly packed collagen fibres in neat rows | Collagen fibres with more stretchy elastic fibres |
| Stretch | Very little, so no pull is wasted | A little more, to allow safe movement |
| Common injury | Strain or tendinitis | Sprain |
| Famous example | The Achilles tendon in the heel | The ACL inside the knee |
| Blood supply | Poor, so healing is slow | Poor, so healing is slow |
How they work together
Take your knee. The big thigh muscle at the front ends in a tendon that runs over the kneecap and joins the shin bone. When the muscle pulls, the tendon pulls the shin and your leg straightens. Inside the knee, ligaments such as the ACL tie the thigh bone to the shin bone so the joint stays lined up while it moves.
Sprain or strain?
A sprain is an injury to a ligament, often when a joint like the ankle is twisted too far. A strain is an injury to a muscle or tendon, often from over-stretching. Both have a poor blood supply compared with muscle, which is why they can take weeks or months to heal.
Quick facts
- The Achilles tendon is the thickest and strongest tendon in the body.
- Tendons are made mostly of collagen, the same protein found in skin.
- The human body has around 4,000 tendons and around 900 ligaments.
- Some ligaments do not join bones to bones at the joints but hold organs in place, such as those that support the liver.
- Cartilage is different again: it is the smooth padding on the ends of bones inside a joint.
See them in 3D
Tendon vs ligament questions
What is the difference between a tendon and a ligament?
A tendon joins a muscle to a bone and passes on the muscle’s pull. A ligament joins one bone to another and holds a joint steady.
Which is stronger, a tendon or a ligament?
Both are very strong. Tendons are built to take large pulling forces in one direction, and the Achilles tendon can handle several times your body weight when you run.
Is the ACL a tendon or a ligament?
A ligament. ACL stands for anterior cruciate ligament. It joins the thigh bone to the shin bone inside the knee.
Is the Achilles a tendon or a ligament?
A tendon. It joins the calf muscles to the heel bone.
Why do tendons and ligaments heal slowly?
They have far fewer blood vessels than muscle, so less oxygen and fewer repair cells reach the injured area.
More face-offs: see all 3D comparisons.
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