Tendons and Ligaments

This lesson covers the role of tendons and ligaments in the musculoskeletal system as required by the AQA GCSE PE specification (3.1.1.1). You need to know what tendons and ligaments are, understand the difference between them, and explain how they support joint stability and enable movement during physical activity.

Tendons and ligaments are both types of connective tissue, but they have different structures, locations, and functions. Confusing the two is one of the most common mistakes in the GCSE PE exam.

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What Are Tendons?

A tendon is a strong, flexible band of fibrous connective tissue that connects muscle to bone.

Structure of Tendons

• Tendons are made primarily of collagen fibres, arranged in parallel bundles. This gives them enormous tensile strength (the ability to resist being pulled apart).
• They are slightly elastic but much less so than muscles — they can stretch slightly but return to their original length.
• Tendons appear white in colour because they have a relatively poor blood supply. This poor blood supply means they heal slowly when injured.
• They are typically cord-like or flat/sheet-like in shape, depending on the muscle they serve.

Function of Tendons

Function	Explanation
Connect muscle to bone	Tendons physically attach the muscle to the bone, allowing the force of muscle contraction to be transmitted to the skeleton
Transmit force	When a muscle contracts, the force is transferred through the tendon to the bone, causing movement at the joint
Enable movement	Without tendons, muscles could not move bones — there would be no connection between the muscular and skeletal systems
Store and release elastic energy	During activities like running and jumping, tendons stretch slightly and then recoil, returning stored energy and improving efficiency

Key Tendons You Should Know

Tendon	Location	Muscle It Connects	Bone It Connects To
Achilles tendon	Back of the ankle	Gastrocnemius (calf muscle)	Calcaneus (heel bone)
Patellar tendon	Front of the knee	Quadriceps	Tibia (via the patella)
Biceps tendon	Front of the elbow	Biceps	Radius
Hamstring tendons	Back of the knee	Hamstrings	Tibia and fibula

The Achilles tendon is the largest and strongest tendon in the body. It is essential for walking, running, jumping, and all activities involving plantarflexion at the ankle.

Exam Tip: A simple way to remember the function of a tendon: Tendon = Ties muscle To bone. Three T's.

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What Are Ligaments?

A ligament is a strong, slightly elastic band of fibrous connective tissue that connects bone to bone across a joint.

Structure of Ligaments

• Ligaments are also made primarily of collagen fibres, but they are arranged in a more criss-cross pattern (rather than the parallel arrangement of tendons). This allows them to resist forces from multiple directions.
• They are slightly more elastic than tendons, allowing some stretching, but they will tear if stretched too far.
• Like tendons, ligaments have a relatively poor blood supply, which means they heal slowly when damaged.
• Ligaments vary in shape — some are cord-like bands, while others are flat sheets.

Function of Ligaments

Function	Explanation
Connect bone to bone	Ligaments hold bones together at joints, maintaining the structural integrity of the joint
Stabilise joints	They prevent excessive or unwanted movement, keeping the bones properly aligned
Prevent dislocation	By restricting movement beyond the normal range, ligaments prevent the bones from separating (dislocating)
Allow normal range of movement	Ligaments are slightly elastic, allowing the joint to move within its intended range while preventing movement beyond that range
Proprioception	Ligaments contain nerve endings that send information to the brain about joint position, helping with balance and coordination

Key Ligaments You Should Know

Ligament	Location	What It Does
Anterior Cruciate Ligament (ACL)	Inside the knee	Prevents the tibia from sliding too far forward relative to the femur; resists rotation
Posterior Cruciate Ligament (PCL)	Inside the knee	Prevents the tibia from sliding too far backward relative to the femur
Medial Collateral Ligament (MCL)	Inside of the knee	Prevents the knee from bending inward (valgus stress)
Lateral Collateral Ligament (LCL)	Outside of the knee	Prevents the knee from bending outward (varus stress)

Exam Tip: A simple way to remember the function of a ligament: Ligament = Links bone to bone. Two L's.

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Tendons vs Ligaments: Key Differences

Feature	Tendon	Ligament
Connects	Muscle to bone	Bone to bone
Primary function	Transmits force from muscle contraction to bone, producing movement	Stabilises joints and prevents excessive/unwanted movement
Fibre arrangement	Parallel bundles	Criss-cross pattern
Elasticity	Slightly elastic	Slightly more elastic than tendons
Blood supply	Poor	Poor
Healing time	Slow	Slow
Common injury	Tendonitis (inflammation), rupture	Sprain (stretching/tearing)
Key example	Achilles tendon	Anterior cruciate ligament (ACL)

graph TD
    A["Connective Tissues at Joints"] --> B["Tendons"]
    A --> C["Ligaments"]
    B --> D["Connect Muscle to Bone"]
    C --> E["Connect Bone to Bone"]
    D --> F["Transmit Force for Movement"]
    E --> G["Stabilise Joints"]
    F --> H["e.g. Achilles tendon enables plantarflexion"]
    G --> I["e.g. ACL prevents tibia sliding forward"]

    style A fill:#4a90d9,color:#fff
    style B fill:#e67e22,color:#fff
    style C fill:#27ae60,color:#fff

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How Tendons and Ligaments Support Joint Stability