At a joint such as the knee, the quadriceps muscle pulls through the patellar tendon to extend the leg, while ligaments such as the ACL and MCL help control joint motion. Tendons must transmit large forces quickly, and ligaments must resist unwanted movement without making the joint too stiff. Their strength comes mainly from collagen fibers arranged to handle tension.
Good training, warmups, technique, and recovery can improve how these tissues handle load and reduce injury risk.
Key Facts
- Tendon function: muscle force is transferred to bone to create movement.
- Ligament function: bone is connected to bone to stabilize a joint.
- Stress = force / area, or σ = F / A.
- Strain = change in length / original length, or ε = ΔL / L0.
- Stiffer tissues stretch less under the same force, which helps with quick force transfer.
- Tendons and ligaments heal slowly because they have less blood flow than muscles.
Vocabulary
- Tendon
- A tendon is a strong connective tissue that attaches muscle to bone and transmits pulling force.
- Ligament
- A ligament is a strong connective tissue that connects bone to bone and helps stabilize a joint.
- Collagen
- Collagen is a tough protein fiber that gives tendons and ligaments much of their tensile strength.
- Joint stability
- Joint stability is the ability of a joint to stay controlled and aligned during movement.
- Strain
- Strain is the fractional change in length of a tissue when it is stretched or loaded.
Common Mistakes to Avoid
- Confusing tendons with ligaments is wrong because tendons connect muscle to bone, while ligaments connect bone to bone.
- Thinking ligaments actively move bones is wrong because ligaments mainly guide and stabilize joints, while muscles and tendons create most movement.
- Ignoring landing technique is wrong because poor alignment can increase stress on knee ligaments and raise injury risk.
- Assuming pain means the tissue should be stretched harder is wrong because injured tendons or ligaments may need reduced load, proper progression, and recovery time.
Practice Questions
- 1 A patellar tendon experiences a pulling force of 1200 N during a jump. If its cross-sectional area is 0.00008 m2, what is the stress in the tendon?
- 2 A ligament is 40 mm long at rest and stretches to 42 mm during a movement. What is its strain?
- 3 During a basketball landing, explain how the quadriceps, patellar tendon, femur, tibia, and knee ligaments work together to control the motion and protect the joint.