Joints & Biomechanics Lecture

Vocabulary flashcards summarizing key terms and definitions related to joint types, synovial structures, muscle attachments, and biomechanical lever concepts.

Synarthrotic joint

Functional joint class that permits no movement; strong, immobile (e.g., skull sutures).

Amphiarthrotic joint

Functional joint class that allows very limited movement (e.g., intervertebral discs).

Diarthrotic joint

Functional joint class that is freely movable; synonymous with synovial joints.

Fibrous joint

Structural joint type united by dense fibrous connective tissue; no synovial cavity.

Cartilaginous joint

Structural joint type united by cartilage; lacks a synovial cavity.

Synovial joint

Freely movable joint characterized by a fluid-filled synovial cavity between bones.

Suture

Fibrous, synarthrotic joint with very thin connective tissue between skull bones.

Syndesmosis

Fibrous, amphiarthrotic joint where bones are connected by a ligament or interosseous membrane (e.g., distal tibiofibular).

Gomphosis

Fibrous, synarthrotic joint that anchors teeth to maxillae/mandible via periodontal ligament.

Synchondrosis

Cartilaginous, synarthrotic joint united by hyaline cartilage (e.g., epiphyseal plate, first rib–sternum).

Symphysis

Cartilaginous, amphiarthrotic joint with fibrocartilage disc between bones (e.g., pubic symphysis).

Articular capsule

Dense irregular connective tissue sleeve in synovial joints that encloses the cavity and unites bones.

Synovial membrane

Inner loose connective tissue layer of articular capsule that produces synovial fluid.

Synovial fluid

Thick fluid that lubricates synovial joints, absorbs shock, provides nutrients, and removes wastes.

Articular cartilage

Hyaline cartilage covering bone ends in synovial joints to reduce friction and absorb shock.

Ligament

Dense regular connective tissue band that strengthens joints by connecting bone to bone.

Tendon

Dense regular connective tissue cord attaching muscle to bone or joint.

Meniscus

C-shaped fibrocartilage pad acting as a spacer and shock absorber in certain joints (e.g., knee).

Bursa

Flattened fluid-filled sac lined with loose CT that reduces friction where structures rub.

Gliding (translation)

Movement where one bone slides over another without changing the joint angle.

Rotation

Movement in which a bone turns around its own longitudinal axis.

Angular movement

Motion that changes the angle between two bones (e.g., flexion, extension, abduction, adduction).

Circumduction

Conical movement where the distal end describes a circle while the shaft outlines a cone.

Pivot joint

Synovial joint with a rounded bone end rotating in a ring; permits rotation only (e.g., atlas–axis).

Hinge joint

Synovial joint with convex/concave surfaces allowing motion in one plane (flexion–extension) (e.g., elbow).

Saddle joint

Synovial joint with saddle-shaped articulations permitting biaxial angular motion plus circumduction (thumb CMC).

Plane (gliding) joint

Synovial joint with flat surfaces allowing sliding movements (e.g., carpal and tarsal joints).

Condyloid (ellipsoidal) joint

Synovial joint with oval convex and concave surfaces allowing biaxial motion and circumduction (e.g., wrist).

Ball-and-socket joint

Synovial joint with spherical head in cup-like socket allowing multiaxial motion and rotation (e.g., shoulder).

Origin (muscle)

Tendon attachment to the relatively stationary bone during contraction.

Insertion (muscle)

Tendon attachment to the more movable bone; moves toward the origin during contraction.

Prime mover (agonist)

Muscle primarily responsible for producing a specific movement.

Antagonist (muscle)

Muscle that opposes or reverses the action of a prime mover.

Synergist

Muscle that assists a prime mover by adding force or stabilizing a joint.

Lever

Rigid bar (bone) that moves on a fixed point (fulcrum) when force is applied.

Fulcrum

Fixed point around which a lever moves; corresponds to a joint.

Effort (force)

Applied muscular force that causes movement of a lever.

Resistance (load)

Body weight or external object that the lever moves.

First-class lever

Lever with fulcrum between effort and load (e.g., neck extension).

Second-class lever

Lever with load between fulcrum and effort; power lever (e.g., standing on tip-toe).

Third-class lever

Lever with effort between fulcrum and load; speed lever (e.g., biceps flexing forearm).

Power lever

Lever system with mechanical advantage (<1 effort/load) emphasizing force over speed.

Speed lever

Lever system with mechanical disadvantage (>1 effort/load) favoring speed and range of motion.

Mechanical advantage

Condition where the effort arm is longer than the resistance arm, reducing required force.

Mechanical disadvantage

Condition where the resistance arm is longer than the effort arm, increasing required force.

Effort arm

Distance from fulcrum to the point where effort is applied.

Resistance arm

Distance from fulcrum to the center of the load.

Antagonist (muscle)

Muscle that opposes or reverses the action of a prime mover.