38.3 Joints and Skeletal Movement
3 min read•june 14, 2024
Joints are the body's connectors, allowing movement and stability. From the rigid of the skull to the flexible of the hips, each type serves a unique purpose. Understanding types and movements is crucial for grasping how our bodies function.
Skeletal movements at joints enable our daily activities. , , , and other motions work together to create complex movements. These movements, along with joint structures like and , form the foundation of human mobility and physical interaction with the world.
Joint Types and Characteristics
Types of joints
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- connect bones with fibrous connective tissue (sutures, , )
- Sutures are interlocking, immovable joints found between skull bones
- Syndesmoses are slightly movable joints where bones are connected by ligaments or interosseous membranes
- Gomphoses are immovable joints found in tooth sockets
- connect bones with cartilage (, )
- are slightly movable joints (, )
- Synchondroses are immovable joints that allow bone growth ( in long bones)
- are the most movable joint type with a enclosing and covering bone ends
- The lines the joint capsule and produces synovial fluid
- are fluid-filled sacs that reduce friction between moving structures in and around joints
Synovial joint shapes and movement
- allow movement in one plane (flexion, extension) and are found in the , , , and
- allow rotation around a central axis (, )
- allow movement in two planes (flexion, extension, , ) and are found in the of the thumb
- allow gliding or sliding movement (intercarpal, intertarsal, )
- allow movement in two planes (flexion, extension, abduction, adduction) and are found in the and
- Ball-and-socket joints allow movement in all three planes (flexion, extension, abduction, adduction, rotation, ) and are found in the and
Skeletal Movements at Joints
Skeletal movements at joints
- Flexion decreases joint angle by bending a joint (elbow, knee)
- Extension increases joint angle by straightening a joint (elbow, knee)
- Abduction moves a body part away from the midline (raising arm laterally)
- Adduction moves a body part toward the midline (lowering arm to the side)
- Rotation turns a body part around a central axis
- Internal (medial) rotation rotates toward the midline
- External (lateral) rotation rotates away from the midline
- Circumduction combines flexion, extension, abduction, and adduction to move a body part in a circular motion (arm)
- rotates the forearm so the palm faces anteriorly or superiorly
- rotates the forearm so the palm faces posteriorly or inferiorly
- flexes the foot at the ankle, moving toes toward the shin
- extends the foot at the ankle, pointing toes away from the shin
- turns the sole of the foot inward
- turns the sole of the foot outward
Joint Structure and Function
- Ligaments connect bones to bones, providing stability and limiting excessive movement
- Tendons connect muscles to bones, transmitting force for movement
- refers to the extent of movement possible at a joint
- is the study of joints and their structure
- applies mechanical principles to analyze movement and forces acting on the body
Key Terms to Review (77)
Abduction: Abduction is a type of movement that involves moving a limb or body part away from the midline of the body. This motion is crucial for various physical activities and is facilitated by specific joints and muscles. Understanding abduction helps in recognizing how our bodies perform tasks, maintain balance, and interact with our environment.
Adduction: Adduction is the movement of a limb or other body part toward the midline of the body. This action is essential in various skeletal movements and plays a critical role in maintaining balance and posture, as well as facilitating coordinated movement during activities like walking, running, and playing sports.
Angular movements: Angular movements involve the change in angle between two bones connected by a joint. These movements include flexion, extension, abduction, adduction, and circumduction.
Ankle: The ankle is a complex joint that connects the foot to the leg, allowing for movement and flexibility in walking, running, and jumping. It consists of several bones, including the tibia, fibula, and talus, and is supported by ligaments and tendons that provide stability while enabling a range of motion. This joint plays a crucial role in weight-bearing activities and contributes to overall balance and coordination.
Arthrology: Arthrology is the branch of anatomy that deals with the study of joints and their movements. This field explores the structure, function, and classifications of joints, which are critical for skeletal movement and play a key role in the overall mobility of the body. Understanding arthrology helps in comprehending how different types of joints contribute to movement and stability in various parts of the skeletal system.
Articular cartilage: Articular cartilage is a smooth, white tissue that covers the ends of bones where they come together to form joints. It plays a critical role in reducing friction between the bones during movement and acts as a shock absorber, helping to distribute loads across the joint surfaces. The health of articular cartilage is essential for maintaining joint function and mobility, as it allows for smooth skeletal movement.
Articulation: Articulation refers to the connection between bones that allows for movement and support. It is a fundamental aspect of the musculoskeletal system, enabling various types of skeletal movements.
Atlantoaxial joint: The atlantoaxial joint is a pivotal joint located between the first cervical vertebra (the atlas) and the second cervical vertebra (the axis). This joint allows for a significant range of motion, particularly enabling the head to rotate from side to side. Its unique structure and function are critical for various movements of the skull and neck, contributing to overall head mobility and stability.
Ball-and-socket joints: Ball-and-socket joints are a type of synovial joint that allows for a wide range of movement in multiple directions. They consist of a spherical head (the ball) that fits into a cup-like socket, providing the ability to rotate and move in various planes, which is essential for many bodily movements. This unique structure makes ball-and-socket joints crucial for activities that require flexibility and mobility, such as reaching, throwing, or dancing.
Biomechanics: Biomechanics is the study of the mechanical laws relating to the movement or structure of living organisms. It combines principles from physics and biology to understand how forces interact with biological systems, influencing movement and stability in various skeletal systems and joints. This field is essential for comprehending how organisms achieve motion and perform complex movements efficiently.
Bursae: Bursae are small, fluid-filled sacs located in joints throughout the body that act as cushions between bones and tendons or muscles around the joints. They play a crucial role in reducing friction, allowing smooth movement and protecting the surrounding tissues from wear and tear during skeletal movement. By facilitating mobility and minimizing the risk of injury, bursae are essential for efficient joint function.
Carpometacarpal joint: The carpometacarpal joint is a complex joint located at the base of the hand, where the carpals meet the metacarpals. It plays a crucial role in hand movement and function, allowing for a wide range of motions such as flexion, extension, abduction, and opposition. This joint structure is vital for grasping and manipulating objects, highlighting its importance in daily activities.
Cartilaginous joints: Cartilaginous joints are types of joints where the bones are connected by cartilage, allowing for limited movement between them. These joints play a crucial role in the flexibility and stability of the skeletal system, accommodating growth and providing shock absorption. They are found in areas such as the spine and the ribcage, which highlights their importance in overall skeletal movement and function.
Chromosome inversion: A chromosome inversion occurs when a segment of a chromosome breaks off, flips around, and reattaches in the reverse direction. This can disrupt gene function and lead to genetic disorders.
Circumduction: Circumduction is a circular movement that occurs at joints, allowing a limb to move in a conical fashion. This motion combines flexion, extension, abduction, and adduction, enabling the distal end of the limb to describe a circular path while the proximal end remains relatively stationary. It is commonly seen in movements of the shoulder and hip joints, facilitating complex motions such as throwing or swinging.
Condyloid joints: Condyloid joints, also known as ellipsoidal joints, are a type of synovial joint that allows for movement in two planes, permitting flexion and extension as well as abduction and adduction. These joints are characterized by an oval-shaped surface of one bone fitting into a similarly shaped cavity of another bone, facilitating a variety of movements while maintaining stability. Common examples of condyloid joints include the wrist joint and the metacarpophalangeal joints, where the ability to move in multiple directions enhances overall mobility and function.
Depression: Depression is a downward movement of a body part, typically referring to the lowering of bones or tissues in the musculoskeletal system. It often occurs at joints and plays a crucial role in various skeletal movements.
Diarthroses: Diarthroses are joints that allow for free movement in various directions. These are also known as synovial joints and are the most common type of joint in the human body.
Dorsiflexion: Dorsiflexion is the movement of bringing the top of the foot closer to the front of the leg, which effectively decreases the angle between the dorsum of the foot and the leg. This action is primarily performed by the muscles located in the anterior compartment of the lower leg and plays a crucial role in various movements, such as walking, running, and jumping. It is an essential motion for proper gait mechanics and overall mobility.
Elbow: The elbow is a hinge joint located between the upper arm and the forearm, primarily facilitating the bending and straightening of the arm. This joint plays a crucial role in various movements, such as lifting and throwing, making it essential for everyday activities. The elbow connects three bones: the humerus, radius, and ulna, allowing for a wide range of motion while maintaining stability.
Elevation: Elevation is the upward movement of a body part, typically referring to the lifting of a limb or joint. This action is commonly seen in movements such as shrugging the shoulders or raising an arm.
Epiphyseal plates: Epiphyseal plates, also known as growth plates, are layers of cartilage found at the ends of long bones in growing individuals. They play a crucial role in bone growth by allowing the lengthening of bones during childhood and adolescence through a process called endochondral ossification. Once growth is complete, these plates ossify and become epiphyseal lines, indicating that further lengthening of the bone can no longer occur.
Eversion: Eversion is the movement of the sole of the foot outward, away from the midline of the body. This action is crucial for various movements and stability, particularly in activities that involve balancing or shifting weight. Eversion primarily occurs at the subtalar joint, allowing the foot to adapt to uneven surfaces, which is essential for maintaining balance and preventing injuries during dynamic activities.
Extension: Extension is the process of increasing the angle between two body parts at a joint, leading to a straightening movement. This action is fundamental in various types of skeletal movement, enabling the limbs to return to a neutral position or to lengthen and reach out. Understanding extension helps in recognizing how different joints function during activities like walking, running, and jumping, as well as its importance in maintaining overall mobility and flexibility.
External rotation: External rotation refers to the movement of a limb or joint away from the midline of the body, resulting in the outward turning of the structure. This type of movement is crucial in various joints, particularly in the shoulder and hip, allowing for a wide range of motions that are essential for many physical activities and functional tasks.
Fibrous joints: Fibrous joints are connections between bones held together by dense connective tissue, primarily collagen. These joints generally allow very little or no movement.
Fibrous joints: Fibrous joints are a type of joint where the bones are connected by dense connective tissue, allowing little to no movement between the bones. These joints play a critical role in providing stability and strength to the skeletal system, especially in areas where rigid support is necessary. The limited mobility of fibrous joints helps maintain the integrity of certain structures, particularly in the skull and between other bones that require a solid connection.
Flexion: Flexion is a type of joint movement that decreases the angle between two body parts, bringing them closer together. This movement is essential for various actions such as bending the elbow or knee, and it plays a critical role in many daily activities and physical exercises. Flexion occurs at various joints in the body and is often paired with its opposite movement, extension, which increases the angle between body parts.
Gliding movements: Gliding movements are a type of joint movement where flat bone surfaces slide over one another. These movements occur in plane joints and allow for limited motion in various directions.
Gomphoses: Gomphoses are a specific type of joint that connects teeth to their sockets in the jawbone, characterized by a peg-and-socket arrangement. This unique joint allows for stability and support for teeth, enabling them to withstand the forces generated during biting and chewing. Gomphoses play an essential role in maintaining oral health and function, highlighting the importance of proper dental alignment and the relationship between teeth and bone structure.
Hinge joints: Hinge joints are synovial joints that allow movement primarily in one plane, similar to the motion of a door hinge. These joints permit flexion and extension movements.
Hinge joints: Hinge joints are a type of synovial joint that allow movement in one plane, primarily flexion and extension, similar to the motion of a door hinge. They are characterized by the convex surface of one bone fitting into the concave surface of another, providing stability and allowing for efficient movement at joints such as the elbow and knee. This specific design enables these joints to support weight and facilitate everyday movements.
Hip: The hip is a ball-and-socket joint that connects the femur (thigh bone) to the pelvis, allowing for a wide range of motion and mobility in the lower body. This joint plays a crucial role in weight-bearing activities, walking, running, and various forms of movement. The structure of the hip joint is designed to provide both stability and flexibility, which is essential for activities such as climbing, bending, and twisting.
Hyperextension: Hyperextension is the movement of a joint beyond its normal range of motion. It can result in injury to ligaments, tendons, or other structures around the joint.
Intercarpal joints: Intercarpal joints are the articulations between the eight carpal bones in the wrist, allowing for a range of movements necessary for hand function. These joints contribute to the overall flexibility and dexterity of the wrist, enabling various actions such as gripping and manipulating objects. They are classified as synovial joints, specifically gliding joints, which facilitate limited movement in multiple directions.
Internal rotation: Internal rotation refers to the movement of a limb or body part toward the center of the body, often occurring at joints such as the shoulder or hip. This action is crucial for a variety of movements and postures, impacting how muscles function and allowing for greater range of motion in certain activities.
Interphalangeal joints: Interphalangeal joints are the hinge joints located between the phalanges (finger and toe bones) that allow for flexion and extension movements. These joints play a vital role in the mobility and dexterity of the fingers and toes, contributing to overall skeletal movement and functionality.
Intertarsal joints: Intertarsal joints are the articulations between the tarsal bones in the foot, allowing for limited movement and contributing to the overall flexibility and stability of the foot. These joints play a significant role in maintaining balance and facilitating locomotion by enabling the foot to adapt to various surfaces. They help in distributing weight during activities like walking, running, and jumping.
Intervertebral discs: Intervertebral discs are fibrocartilaginous cushions situated between the vertebrae of the spine. They provide flexibility and absorb shock to maintain spinal integrity during movement.
Intervertebral discs: Intervertebral discs are fibrocartilaginous structures located between the vertebrae in the spinal column, serving as shock absorbers and allowing for flexibility and movement of the spine. These discs consist of a tough outer layer called the annulus fibrosus, which encases a softer, gel-like center known as the nucleus pulposus. They play a critical role in maintaining the integrity of the spinal column and facilitating movement, making them essential in the study of vertebrate anatomy and joint mechanics.
Inversion: Inversion refers to a chromosomal alteration where a segment of a chromosome is reversed end to end. This rearrangement can affect gene expression and may lead to various inherited disorders, as it alters the normal structure of the chromosome. In the context of musculoskeletal system function, inversion also describes a movement where a body part turns inward, specifically concerning joint and skeletal movement mechanics.
Joint: A joint is a structure where two or more bones are connected, allowing for movement and support. Joints can be classified based on their structure and function, such as synovial, fibrous, and cartilaginous joints.
Joint capsule: The joint capsule is a fibrous tissue structure that surrounds and encases a synovial joint, providing stability and protection while allowing for a range of motion. This structure is critical for maintaining the integrity of the joint, as it holds the synovial fluid within the joint space, lubricating the joint surfaces and facilitating smooth movement. The joint capsule consists of an outer fibrous layer and an inner synovial membrane that produces the synovial fluid.
Knee: The knee is a complex hinge joint that connects the thigh bone (femur) to the shin bone (tibia) and plays a crucial role in movement and stability of the leg. It allows for flexion and extension, enabling activities like walking, running, and jumping, while also providing support and bearing weight. The knee is supported by ligaments, cartilage, and tendons, making it one of the most important joints in the body for both mobility and load distribution.
Lateral rotation: Lateral rotation is a movement where a limb or body part rotates away from the midline of the body. This type of rotation occurs in joints like the shoulder and hip.
Ligaments: Ligaments are tough bands of connective tissue that connect bones to other bones at joints, providing stability and support to the skeletal system. They play a crucial role in maintaining joint integrity and allowing for controlled movement by limiting excessive motion. Ligaments are essential in the structure of various skeletal systems and are key components in how joints function during movement.
Medial rotation: Medial rotation is the inward turning of a bone around its long axis towards the center of the body. It is a type of movement that occurs at synovial joints, particularly ball-and-socket and hinge joints.
Metacarpophalangeal joints: Metacarpophalangeal joints (MCP joints) are the hinge-like connections between the metacarpal bones of the hand and the proximal phalanges of the fingers. These joints play a crucial role in hand function, allowing for a wide range of movements such as flexion, extension, abduction, and adduction, contributing significantly to dexterity and grip strength.
Opposition: Opposition is the movement that brings the thumb and fingers together, enabling grasping and manipulation of objects. It is a key function of the hand, involving coordinated actions of muscles, bones, and joints.
Pivot joints: Pivot joints are a type of synovial joint that allows for rotational movement around a single axis. They enable the bones to move in a twisting motion, which is essential for various skeletal movements. An example of pivot joints can be seen in the neck and forearm, where they facilitate critical movements such as turning the head and rotating the wrist.
Planar joints: Planar joints, also known as gliding joints, are a type of synovial joint where the articulating surfaces are flat or slightly curved. These joints allow for limited movement, primarily sliding actions between bones.
Plane joints: Plane joints are a type of synovial joint where two flat or slightly curved bone surfaces glide over one another, allowing for limited movement in multiple directions. This joint structure is crucial for facilitating smooth and controlled skeletal movements, enabling actions such as gliding and sliding between bones. Plane joints play a key role in maintaining stability while allowing a range of motion, especially in areas such as the wrists and ankles.
Plantar flexion: Plantar flexion is the movement that decreases the angle between the foot and the lower leg, allowing the toes to point downward. This motion primarily involves the ankle joint and is crucial for activities such as walking, running, and jumping. It engages several muscles in the calf region, especially the gastrocnemius and soleus, which work together to facilitate this action.
Pronation: Pronation is a specific movement that occurs at the joints, particularly in the forearm and foot, characterized by the inward rotation or tilting of a structure. In the context of the forearm, it involves turning the palm downwards or backwards, while in the foot, it refers to the rolling inward of the ankle during walking or running. Understanding pronation is essential for analyzing movement patterns and identifying potential biomechanical issues related to joint function and overall skeletal movement.
Protraction: Protraction is the anterior movement of a body part in the horizontal plane. It commonly involves movements such as bringing the shoulder blades forward.
Pubic symphysis: The pubic symphysis is a cartilaginous joint located between the left and right pubic bones in the pelvis, allowing for limited movement during activities such as walking or childbirth. This joint plays a crucial role in maintaining pelvic stability and providing flexibility, especially during pregnancy when hormonal changes increase its mobility to facilitate delivery.
Radiocarpal joint: The radiocarpal joint is a complex synovial joint located in the wrist, formed between the distal end of the radius and the first row of carpal bones. This joint allows for a wide range of movements, including flexion, extension, abduction, and adduction, making it crucial for hand function and dexterity. It is supported by ligaments that provide stability while permitting the mobility necessary for various daily tasks.
Radioulnar joint: The radioulnar joint is a pivotal joint formed between the radius and the ulna, two bones of the forearm. It plays a crucial role in allowing rotational movement of the forearm, which is essential for various activities such as turning a doorknob or using a screwdriver. This joint consists of two distinct articulations: the proximal radioulnar joint located near the elbow and the distal radioulnar joint located near the wrist.
Range of Motion: Range of motion refers to the full movement potential of a joint, typically measured in degrees of a circle. It is a crucial aspect of joint health, flexibility, and overall mobility, influencing how well individuals can perform daily activities and engage in physical exercise. Factors such as joint structure, muscle length, and the surrounding connective tissues play significant roles in determining the range of motion.
Retraction: Retraction is the movement of a body part in the posterior direction, toward the back of the body. It commonly occurs in joints such as the shoulder blades and jaw.
Rotation: Rotation refers to the circular movement of an object around a center point or axis. In the context of joints and skeletal movement, rotation is essential for allowing various parts of the body to turn and pivot in different directions, enabling a wide range of motions necessary for everyday activities and sports.
Rotational movement: Rotational movement is the motion of a body part around its own axis. It is a type of angular movement commonly facilitated by joints.
Saddle joints: Saddle joints are a type of synovial joint characterized by two bone ends that resemble the shape of a saddle, allowing for a range of motion in multiple directions. This unique shape enables movements such as flexion, extension, abduction, and adduction, making them highly versatile for skeletal movement. The most well-known example of a saddle joint in the human body is the carpometacarpal joint of the thumb, which allows for the grasping and manipulation of objects.
Shoulder: The shoulder is a complex joint structure that connects the arm to the torso, allowing for a wide range of motion and mobility. It consists of multiple components including the humerus, scapula, and clavicle, along with ligaments and muscles that stabilize and facilitate movement. The shoulder's design enables various types of skeletal movement, making it essential for numerous daily activities and athletic performances.
Sternoclavicular joints: Sternoclavicular joints are the synovial joints located where the clavicle meets the sternum at the breastbone. These joints play a crucial role in connecting the upper limb to the axial skeleton, allowing for a range of movements such as elevation, depression, and rotation of the shoulder girdle, which is essential for various arm motions.
Supination: Supination is the movement that involves rotating the forearm and hand so that the palm faces upward or forward. This motion is crucial for various activities, such as holding objects, and plays a significant role in the mechanics of the arm and wrist during different movements. Supination is often paired with pronation, which is the opposite motion, and together they are essential for understanding how joints and skeletal movement function in everyday life.
Sutures: Sutures are fibrous joints that connect the bones of the skull. They are characterized by a thin layer of dense connective tissue that allows very little movement, providing stability and protection for the brain. Sutures play a crucial role in the growth and development of the skull, allowing for expansion as the brain grows during infancy and childhood.
Symphyses: Symphyses are a type of cartilaginous joint where bones are united by fibrocartilage. These joints offer limited movement and significant strength, typically found in the midline of the body.
Symphyses: Symphyses are a type of cartilaginous joint where the bones are connected by a pad of fibrocartilage. This type of joint allows for limited movement, providing flexibility and support to the skeletal structure. Symphyses are crucial for absorbing shock and maintaining stability in areas like the pelvis and vertebral column, making them essential for overall skeletal movement.
Synarthrosis: Synarthrosis is a type of joint that permits little or no mobility. These joints are typically fibrous and found in locations where stability is crucial, such as the sutures of the skull.
Synchondroses: Synchondroses are a type of cartilaginous joint where the bones are connected by hyaline cartilage. These joints allow for limited movement and play an essential role in growth and development, especially in the early stages of life. They are characterized by their temporary nature, often found in the growth plates of long bones and some structures in the rib cage.
Synchondrosis: Synchondrosis is a type of cartilaginous joint where bones are joined by hyaline cartilage. It allows for very little movement and is typically found in the growth plates of children.
Syndesmoses: Syndesmoses are a type of fibrous joint where two bones are connected by a ligament or an interosseous membrane. This type of joint allows for slight movement between the bones, which is essential for stability and flexibility in certain areas of the body, especially in the forearm and lower leg. Syndesmoses play a crucial role in providing support while still permitting limited motion, making them important for various physical activities.
Synovial fluid: Synovial fluid is a viscous, egg-white-like substance that lubricates the joints in the body, providing cushioning and reducing friction between articular cartilage during movement. It is essential for maintaining healthy joints and plays a key role in the overall function of synovial joints, which are the most common type of joints found in the body. This fluid also nourishes the cartilage, helping to keep it healthy and functioning properly.
Synovial joints: Synovial joints are highly mobile joints characterized by a synovial cavity filled with fluid, allowing for a wide range of motion between the articulating bones. These joints are crucial for skeletal movement, as they facilitate actions like bending, rotating, and gliding. The structure of synovial joints also includes various supportive elements such as ligaments and cartilage, which enhance stability and reduce friction during movement.
Synovial membrane: The synovial membrane is a specialized connective tissue that lines the inner surface of synovial joints, which are the most common and movable type of joints in the body. This membrane plays a vital role in joint health by producing synovial fluid, which lubricates the joint and reduces friction during movement. By facilitating smooth movement and providing nutrients to the cartilage, the synovial membrane contributes significantly to skeletal movement.
Tendons: Tendons are strong connective tissues that attach muscles to bones, playing a crucial role in the movement of the skeletal system. They are composed primarily of collagen fibers, which provide them with tensile strength and resistance to stretching. Tendons enable the transfer of force generated by muscle contractions to the skeletal system, facilitating joint movement and overall locomotion.