Kinesiology Notes: Bone Landmarks, Origins, and Insertions

Bony Landmarks

• Bony landmarks are specific locations on bones where muscles attach.

• There are many different kinds of landmarks.

Types of Bony Landmarks

• Condyle: A rounded projection coming off a bone at an articulation.

• Epicondyle: Part of the bone located proximal to the condyle.

• Crest: A thin ridge of a bone.

• Facet: A smooth articular surface of a bone.

• Fissure: A narrow opening, resembling a crack.

• Foramina (foramen): A hole or opening in a bone.

• Fossa: A shallow depression in a bone.

• Linea: A narrow ridge, less pronounced than a crest.

• Meatus: A canal-like passage.

• Process: A prominent structure on a bone.

• Ramus: An elongated, seemingly stretched-out part of a bone.

• Sinus: A cavity created by bones.

• Suture: A type of synarthrotic joint that doesn't allow movement.

• Trochanter: A very large process, only found on the femur.

• Tubercle: A small, rounded projection.

• Tuberosity: A large, rounded, often rough projection.

Naming of Landmarks

• Landmarks are named after their:

  • Type (as listed above)

  • Appearance (e.g., "coracoid" means "resembling a crow's beak")

  • Attached muscles (e.g., deltoid tuberosity)

  • Location in the body (e.g., anterior superior iliac spine)

Origins and Insertions

• Muscles have two different attachments: origins and insertions.

Origins

• The origin of a muscle is where the muscle "begins."

• It is the anchor point of the muscle.

• The origin of a muscle does not produce movement, except in certain cases where the insertion is locked in place.

  • Example: If the shoulders are locked in an adducted position, the latissimus dorsi's origin at the iliac crest may elevate the hip unilaterally, with the shoulder staying in place and not moving.

• Position:

  • For muscles that control a limb, the origin will always be more proximal than the insertion.

    • Example: The origins of the biceps brachii are both located on the scapula, and the insertion is located on the radius. The scapula is more proximal than the radius.

  • For muscles that control the trunk, the origin is generally going to be more medial than the insertion.

    • Example: The rhomboids originate on the spinous processes of C7-T5, and insert onto the medial border of the scapula. The medial border of the scapula is more lateral than the spinous processes of C7-T5.

    • Note: This rule doesn't apply to every muscle of the trunk.

Insertions

• Insertions are the part of the muscle where action takes place.

• When the muscle contracts, it pulls on the tendon attaching to the bony landmark at the insertion point.

• This results in the insertion being pulled toward the origin as the muscle length decreases due to the concentric contraction.

  • Example: When brachialis contracts, its insertions located at the coronoid process of the ulna and ulnar tuberosity will be pulled toward the origin, located at the anterior distal shaft of the humerus.

• When a muscle performs a concentric contraction, an action will occur.

• This is the result of the muscle crossing a joint.

• If a muscle crosses a joint, such as brachialis crossing the elbow, the elbow will move when the insertion is pulled to the origin.

  • In this specific example, a concentric contraction of brachialis will produce elbow flexion.