9.6 Anatomy of Selected Synovial Joints
3 min read•june 18, 2024
Synovial joints are crucial for movement in the human body. They connect bones, allowing for a wide range of motions. From the shoulder's ball-and-socket to the knee's modified hinge, each joint has a unique structure that determines its function and mobility.
Supporting structures play a vital role in and health. , cartilage, and muscles work together to protect joints from injury. These elements ensure smooth movement while maintaining proper alignment and preventing excessive motion.
Bones and Movements of Major Synovial Joints
Bones of major synovial joints
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- Shoulder joint () articulates between the rounded head of the and the shallow glenoid cavity of the scapula
- Elbow joint is formed by the distal end of the , the proximal end of the , and the head of the
- Hip joint () is a connection between the rounded head of the and the of the (hip bone)
- involves the articulation of the distal end of the femur, the proximal end of the , and the (kneecap)
- () is formed by the distal ends of the tibia and , and the bone of the foot
Range of movements in synovial joints
- Shoulder joint is a allowing a wide range of movements including , , , , , , and
- Elbow joint is a primarily allowing and extension movements
- Hip joint is a ball and socket joint permitting flexion, extension, , , medial rotation, lateral rotation, and
- is a modified hinge joint that enables flexion, extension, and slight medial and lateral rotation when the joint is flexed
- is a hinge joint that allows (flexion) and (extension) movements of the foot
- The in each joint is influenced by factors such as joint structure, ligament tension, and muscle flexibility
Supporting Structures and Joint Stability
Supporting structures of synovial joints
- is a fibrous connective tissue that surrounds the joint providing stability and limiting excessive movement
- Ligaments are strong, fibrous connective tissues that connect bones and prevent abnormal or excessive joint movements ( in the shoulder, in the elbow and knee, in the hip)
- covers the ends of articulating bones providing a smooth, low-friction surface for joint movement and helping distribute forces across the joint surface
- are crescent-shaped fibrocartilaginous discs in the knee joint that provide stability, shock absorption, and improve congruence between the femur and tibia
- are fluid-filled sacs located near joints that reduce friction between moving structures, such as and bones
- Muscles and tendons provide dynamic stability to the joint during movement and help maintain proper joint alignment and prevent excessive movement
- The lines the inner surface of the joint capsule and produces , which lubricates the joint and nourishes the
Joint Stability and Function
- Joint stability is maintained through a combination of static stabilizers (ligaments, joint capsule) and dynamic stabilizers (muscles, tendons)
- reduces friction between articulating surfaces and provides nutrition to the articular cartilage
- The regulates the production and composition of synovial fluid
- Ligaments limit excessive joint movement and guide normal joint motion
- Tendons transmit muscle forces to bones, contributing to joint movement and stability
Key Terms to Review (92)
Abduction: Abduction in anatomy and physiology is the movement of a limb or other part away from the midline of the body or from another part. It is a key action in joints, enabling movements such as spreading the fingers or arms.
Abduction: Abduction is the movement of a limb or body part away from the midline of the body. It is one of the primary types of body movements that occur at synovial joints, allowing for a wide range of motion and flexibility in the limbs and extremities.
Acetabular labrum: The acetabular labrum is a ring of cartilage that surrounds the acetabulum (the socket) in the hip joint, enhancing its depth and stability by providing a suction seal and limiting the movement of the head of the femur (thigh bone) within the socket. This cartilaginous structure helps distribute pressure, reduce friction, and cushion the joint during movement.
Acetabulum: The acetabulum is a deep, cup-shaped socket located on the lateral aspect of the pelvis that articulates with the head of the femur to form the hip joint. It is formed by parts of the ilium, ischium, and pubis bones of the pelvic girdle.
Acetabulum: The acetabulum is the cup-shaped socket on the lateral side of the hip bone that forms part of the hip joint. It is a key anatomical feature in the pelvic girdle and a critical component of the synovial hip joint.
Adduction: Adduction is a movement that brings a limb closer to the midline of the body or decreases the angle between two bones at a joint. It is opposite to abduction, which moves limbs away from the body's midline.
Adduction: Adduction is a type of body movement that involves the action of moving a limb or body part towards the midline of the body. It is a key concept in understanding the mechanics of the pectoral girdle, synovial joints, and the muscles that control movement of the upper and lower limbs.
Ankle joint: The ankle joint, also known as the talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower leg with the proximal end of the talus in the foot. It allows for dorsiflexion and plantarflexion of the foot, enabling movements such as walking, running, and jumping.
Ankle Joint: The ankle joint, also known as the talocrural joint, is a synovial hinge joint that connects the lower leg to the foot. It is responsible for the up-and-down movements of the foot, allowing for walking, running, and other locomotor activities.
Annular ligament: The annular ligament is a strong band of fibrous tissue that encircles the head of the radius, securing it in place within the elbow joint. It allows for the rotation of the forearm while maintaining stability between the radius and ulna.
Anterior cruciate ligament: The anterior cruciate ligament is one of the key ligaments that help stabilize the knee joint by connecting the thigh bone (femur) to the shin bone (tibia). It prevents the tibia from sliding out in front of the femur and provides rotational stability to the knee.
Anterior talofibular ligament: The anterior talofibular ligament is a band of tissue that connects the talus bone in the ankle to the fibula, one of the bones in the lower leg. It plays a crucial role in stabilizing the ankle joint and preventing excessive inward turning of the foot.
Articular cartilage: Articular cartilage is a smooth, white tissue that covers the ends of bones where they come together to form joints. Its main function is to reduce friction and absorb shock in synovial joints, facilitating smooth and pain-free movement.
Articular Cartilage: Articular cartilage is the smooth, slippery connective tissue that covers the ends of bones where they meet to form a joint. It plays a crucial role in the function and movement of synovial joints by providing a low-friction surface that allows for smooth, pain-free articulation between the bones.
Atlanto-occipital joint: The atlanto-occipital joint is a synovial joint that connects the atlas (the first cervical vertebra) to the occipital bone of the skull, allowing for nodding and slight lateral movement of the head. It is a pivotal component in the mechanics of neck movement and head stabilization.
Ball and Socket Joint: A ball and socket joint is a type of synovial joint where a rounded, ball-like projection of one bone fits into a cup-like socket of another bone, allowing for a wide range of motion in multiple directions. This type of joint is found in the shoulder and hip, enabling the limbs to move freely in a variety of planes.
Bursae: Bursae are small, fluid-filled sacs located throughout the body that provide cushioning and reduce friction between tissues, particularly around joints. They play a key role in facilitating smooth movement by allowing muscles and tendons to glide over bones and other structures. Understanding bursae is essential when looking at joint classification, particularly synovial joints, where they are most commonly found.
Calcaneofibular ligament: The calcaneofibular ligament is a band of tissue that connects the fibula (a bone in the lower leg) to the calcaneus (heel bone), providing stability to the lateral side of the ankle joint. It plays a crucial role in preventing excessive inversion and supporting ankle movement.
Circumduction: Circumduction is a circular movement of a body part, such as an arm or leg, that combines flexion, extension, abduction, and adduction in a continuous sequence. It allows the distal end of the limb to move in a circle while the proximal end remains stationary.
Circumduction: Circumduction is a type of complex joint movement that involves the circular motion of a body part around an axis. It is a combination of the four basic movements: flexion, extension, abduction, and adduction, allowing for a wide range of motion in a joint.
Collateral Ligaments: Collateral ligaments are strong bands of connective tissue that run along the sides of certain synovial joints, providing stability and limiting excessive movement. They are particularly important in the anatomy and function of selected synovial joints.
Coracohumeral ligament: The coracohumeral ligament is a strong band of fibrous tissue that connects the coracoid process of the scapula to the greater tubercle of the humerus. It plays a crucial role in stabilizing the shoulder joint, especially limiting external rotation and preventing downward dislocation of the humerus.
Coxal Joint: The coxal joint, also known as the hip joint, is a ball-and-socket type of synovial joint that connects the femur (thigh bone) to the pelvis. It is the largest and one of the most stable joints in the human body, allowing a wide range of motion and supporting the weight of the upper body.
Deltoid ligament: The deltoid ligament is a strong, triangular band of tissue that connects the medial malleolus of the tibia to various bones of the foot. It serves as a major stabilizing structure for the ankle joint, preventing excessive eversion (outward turning) of the foot.
Dorsiflexion: Dorsiflexion is the action of lifting the foot upwards towards the shin, decreasing the angle between the dorsum (upper surface) of the foot and the leg. It occurs at the ankle joint and is essential for many phases of walking or running.
Dorsiflexion: Dorsiflexion is a type of body movement that involves the upward bending of the foot at the ankle joint, bringing the top of the foot closer to the shin. This movement is essential for various activities and is closely associated with the anatomy and function of the synovial joints in the lower limbs.
Extension: Extension refers to the movement of a joint or body part that increases the angle between the bones involved, straightening or lengthening the limb or structure. It is one of the fundamental types of body movements that occurs at synovial joints and is facilitated by the contraction of specific muscle groups.
Femoropatellar joint: The femoropatellar joint is the point of articulation between the patella (kneecap) and the femur (thigh bone), functioning within the knee as a type of synovial joint. It facilitates movements such as bending and straightening of the knee, playing a critical role in walking, running, and jumping.
Femur: The femur is the longest and strongest bone in the human body, located in the thigh, and plays a crucial role in supporting weight and facilitating movement. Its unique structure allows it to bear significant loads, connecting the pelvis to the knee and serving as an essential component of the lower limb's anatomy and function.
Fibula: The fibula is the smaller of the two bones in the lower leg, located on the lateral side of the tibia. It plays an important role in the skeletal system, lower limb development, and various joints and muscles of the lower extremity.
Fibular collateral ligament: The fibular collateral ligament is a strong band of tissue that connects the femur to the fibula, stabilizing the lateral aspect of the knee joint. It plays a crucial role in preventing excessive inward movement of the knee.
Flexion: Flexion is the action of bending a joint or limb in the body which decreases the angle between the bones of the limb at the joint. It is a fundamental movement in daily activities and exercises, contrasting with extension which increases the angle.
Flexion: Flexion is a type of body movement that decreases the angle between two body parts, bringing them closer together. This term is closely related to the structure and function of muscles, the pectoral girdle, synovial joints, and various body movements and joint anatomy.
Glenohumeral joint: The glenohumeral joint is the ball-and-socket joint where the head of the humerus fits into the shallow socket of the scapula, allowing a wide range of movement for the upper arm. It is a key component of the shoulder's flexibility and stability.
Glenohumeral Joint: The glenohumeral joint, also known as the shoulder joint, is the main joint of the shoulder that allows for a wide range of motion in the upper limb. It is a ball-and-socket type of synovial joint formed by the articulation between the rounded head of the humerus and the shallow, cup-like glenoid cavity of the scapula.
Glenohumeral ligament: The glenohumeral ligament is a group of three ligaments in the shoulder that connect the head of the humerus to the glenoid fossa of the scapula, providing stability to the shoulder joint. These ligaments help limit excessive movement and are key components in maintaining shoulder joint integrity during motion.
Glenohumeral Ligaments: The glenohumeral ligaments are a group of ligaments that connect the head of the humerus to the glenoid cavity of the scapula, forming the shoulder joint. These ligaments provide stability and limit the range of motion in the glenohumeral joint, which is a ball-and-socket joint.
Glenoid labrum: The glenoid labrum is a fibrocartilaginous rim attached around the margin of the glenoid cavity in the shoulder joint, which deepens the cavity and helps stabilize the joint. It acts as a "bumper" that cushions the head of the humerus and allows for a wider range of motion.
Hinge Joint: A hinge joint is a type of synovial joint that allows for flexion and extension movements in a single plane, much like the opening and closing of a door. It is one of the most common types of synovial joints found in the body.
Humeroradial joint: The humeroradial joint is a synovial joint in the elbow that involves the head of the radius and the capitulum of the humerus. It allows for bending and extension as well as some rotational movements of the forearm.
Humeroulnar joint: The humeroulnar joint is a hinge type of synovial joint located between the humerus (upper arm bone) and the ulna (one of the forearm bones), allowing for bending and straightening of the elbow. This joint plays a crucial role in the movement and stability of the arm.
Humerus: The humerus is the long bone in the upper arm that runs from the shoulder to the elbow, connecting with both the scapula at the shoulder joint and the radius and ulna at the elbow joint. It plays a critical role in both the mobility and stability of the upper limb.
Humerus: The humerus is the upper arm bone, connecting the shoulder to the elbow. It is the longest, largest, and strongest bone in the upper limb and plays a crucial role in the structure and function of the arm and shoulder.
Hyperextension: Hyperextension is the movement of a joint beyond its normal range of motion, resulting in an excessive straightening or opening angle. This action can occur in various joints, such as the knee, elbow, and spine, potentially leading to injury if performed excessively.
Iliofemoral ligament: The iliofemoral ligament is a strong band of fibrous tissue that connects the pelvis (ilium) to the femur (thigh bone) at the hip joint. It helps limit hyperextension of the hip, maintaining stability and proper posture during movement.
Iliofemoral Ligament: The iliofemoral ligament is a strong, Y-shaped ligament that connects the ilium of the hip bone to the femur. It is an important stabilizer of the hip joint, playing a crucial role in the anatomy of selected synovial joints.
Ischiofemoral ligament: The ischiofemoral ligament is a strong, fibrous band that connects the ischium part of the pelvis to the femur, stabilizing the back of the hip joint. It helps limit excessive extension and internal rotation of the hip.
Joint Capsule: The joint capsule is a fibrous structure that surrounds and encloses the articulating ends of bones in a synovial joint, providing stability and limiting the range of motion. It is an essential component that helps maintain the integrity of the joint and facilitate smooth, controlled movements.
Joint Stability: Joint stability refers to the ability of a joint to maintain its proper alignment and function without excessive movement or dislocation. It is a critical factor in the overall health and function of the musculoskeletal system, as it ensures the efficient and safe transfer of forces between body segments during movement and activity.
Knee joint: The knee joint is a complex hinge joint that connects the thigh bone (femur) to the shin bone (tibia), allowing for flexion, extension, and slight rotation of the leg. It is reinforced by ligaments, tendons, and muscles that provide stability and facilitate movement.
Knee Joint: The knee joint is a complex hinge joint that connects the thigh bone (femur) to the shin bone (tibia), allowing for flexion, extension, and some rotation of the leg. It is a crucial component of the lower limb and plays a vital role in locomotion and weight-bearing activities.
Lateral condyle of the tibia: The lateral condyle of the tibia is one of two rounded prominences located at the upper part of the tibia (shinbone), specifically on its outer side, where it articulates with the femur and fibula to form part of the knee joint. It serves as a site for muscle attachment and plays a crucial role in supporting the body's weight during movement.
Lateral meniscus: The lateral meniscus is a C-shaped piece of fibrocartilage located on the outer side of the knee, between the thigh bone (femur) and the shin bone (tibia), acting as a cushion to distribute weight and reduce friction during movement. It plays a crucial role in the stability and smooth operation of the knee joint.
Lateral Rotation: Lateral rotation refers to the rotational movement of a body part or joint around its longitudinal axis, where the distal end of the structure moves away from the midline of the body. This movement is an essential component in the anatomy and function of various synovial joints, as well as the coordinated actions of the muscles of the pectoral girdle, upper limbs, pelvic girdle, and lower limbs.
Lateral tibiofemoral joint: The lateral tibiofemoral joint is one of the two compartments in the knee where the lateral condyle of the femur and the lateral condyle of the tibia meet, allowing for movement such as flexion and extension. It is a type of synovial joint that plays a crucial role in weight-bearing and locomotion.
Ligaments: Ligaments are flexible, fibrous connective tissue structures that connect bones to bones, stabilizing and supporting the skeletal system. They play a crucial role in the classification, anatomy, and development of joints throughout the body.
Medial meniscus: The medial meniscus is a C-shaped piece of fibrocartilage located in the knee joint, between the femur (thigh bone) and the tibia (shin bone), that acts as a shock absorber and stabilizes the joint. It helps distribute body weight evenly across the knee joint to reduce wear on the articular cartilage.
Medial Rotation: Medial rotation refers to the movement of a body part, such as a joint or limb, around its longitudinal axis towards the midline of the body. This action involves the rotation of a structure in a direction that brings it closer to the body's central axis.
Medial tibiofemoral joint: The medial tibiofemoral joint is the inner portion of the knee where the medial condyle of the femur and the medial condyle of the tibia meet. It is a critical component of the knee's synovial joint, facilitating movement and weight-bearing.
Menisci: Menisci are crescent-shaped fibrocartilaginous structures found in certain synovial joints, such as the knee, that serve to stabilize the joint, distribute weight, and provide shock absorption during movement.
Os Coxae: The os coxae, commonly known as the hip bone, is the large, irregularly shaped bone that forms the main structure of the pelvic girdle. It plays a crucial role in the anatomy and function of the pelvis and selected synovial joints.
Patella: The patella, commonly known as the kneecap, is a small, flat, and triangular bone located at the front of the knee joint. It is the largest sesamoid bone in the human body and plays a crucial role in the mechanics and function of the knee joint.
Patellar ligament: The patellar ligament is a strong, flat band of fibrous tissue that extends from the patella (kneecap) to the tibia (shinbone), playing a crucial role in extending the knee joint. It is an extension of the quadriceps tendon and is integral to knee stability and movement.
Plantarflexion: Plantarflexion is the movement of the foot that involves the pointing or flexing of the toes downward, away from the body. It is one of the primary motions of the ankle joint and is crucial for various movements and activities involving the lower limbs.
Posterior cruciate ligament: The posterior cruciate ligament is one of the four major ligaments in the knee, connecting the femur (thigh bone) to the tibia (shin bone) at the back of the knee. It prevents the tibia from moving backwards too far in relation to the femur.
Posterior talofibular ligament: The posterior talofibular ligament is a strong, fibrous tissue that connects the talus bone in the ankle to the fibula, one of the bones in the lower leg, at their posterior (back) aspects. This ligament plays a crucial role in stabilizing the ankle joint and limiting its movement to prevent excessive motion that could lead to injury.
Pubofemoral ligament: The pubofemoral ligament is a band of connective tissue that extends from the pubic portion of the pelvis to the femur, reinforcing the anterior part of the hip joint capsule. It helps limit excessive extension and abduction (movement away from the midline) of the thigh, contributing to joint stability.
Radial collateral ligament: The radial collateral ligament is a band of fibrous tissue located in the elbow joint, connecting the lateral epicondyle of the humerus to the radius. It stabilizes the lateral aspect of the elbow, preventing excessive movement that could lead to injury.
Radius: The radius is one of the two bones that make up the forearm, located on the lateral (thumb) side. It is responsible for rotating the forearm and wrist, allowing for a wide range of motion in the upper limb.
Range of Motion: Range of motion (ROM) refers to the measurement of the amount of movement a joint can achieve before it reaches its functional or anatomical limit. It is an important concept in the context of joint classification, synovial joint structure, types of body movements, and the anatomy of specific synovial joints.
Rotator cuff: The rotator cuff is a group of four muscles and their tendons that stabilize the shoulder joint by holding the head of the humerus firmly within the shallow socket of the scapula. These muscles work together to allow a wide range of motion in the arm, including lifting and rotating.
Shaft of the radius: The shaft of the radius is the long, central part of the radius bone in the forearm, extending from below the head near the elbow to just above the wrist where it widens to form part of the wrist joint. It serves as a major structural component of the forearm, providing attachment sites for muscles and supporting movements of the wrist and hand.
Subacromial bursa: The subacromial bursa is a fluid-filled sac located under the acromion of the shoulder, serving as a cushion to reduce friction between the acromion and the tendon of the supraspinatus muscle during arm movement. It plays a crucial role in facilitating smooth, pain-free motion of the shoulder joint.
Subscapular bursa: The subscapular bursa is a fluid-filled sac located between the subscapularis muscle and the scapula bone, serving to reduce friction during muscle movement. It plays a critical role in shoulder mobility and helps prevent damage to the underlying tissues during physical activities.
Subtalar joint: The subtalar joint is a synovial joint located between the talus and the calcaneus bones in the foot, allowing for inversion and eversion movements. It plays a crucial role in adapting to uneven terrain and in the initiation of the gait cycle.
Suspensory ligaments: Suspensory ligaments are fibrous connective tissues that secure the ovaries to the lateral pelvic walls, providing support and maintaining their position in the female reproductive system. They contain blood vessels and nerves that supply the ovaries.
Synovial fluid: Synovial fluid is a viscous, non-Newtonian fluid found in the cavities of synovial joints, serving as a lubricant to reduce friction between the articular cartilages during movement. It also provides nutrients to the cartilages and acts as a shock absorber.
Synovial Fluid: Synovial fluid is a viscous, lubricating liquid found in the synovial joints of the body. It plays a crucial role in reducing friction, providing cushioning, and nourishing the articular cartilage within these joints. This fluid is closely connected to the topics of tissue types, joint classification, synovial joint anatomy, and body fluid compartments.
Synovial membrane: The synovial membrane is a specialized connective tissue that lines the inner surface of capsules in synovial joints and secretes synovial fluid. This fluid lubricates the joint, reducing friction and wear between cartilages during movement.
Synovial Membrane: The synovial membrane is a thin, specialized connective tissue lining the inside of synovial joints, such as the knee, shoulder, and elbow. It plays a crucial role in the anatomy and function of these movable joints by producing synovial fluid and facilitating smooth, frictionless movement.
Talocrural joint: The talocrural joint, also known as the ankle joint, involves the articulation between the talus bone of the foot and the tibia and fibula bones of the leg. It is a hinge type of synovial joint that allows for dorsiflexion and plantarflexion movements of the foot.
Talocrural Joint: The talocrural joint, also known as the ankle joint, is a synovial hinge joint located at the distal end of the leg and the proximal end of the foot. It is responsible for the flexion and extension movements of the foot, which are essential for activities such as walking, running, and standing.
Talus: The talus is a small bone in the ankle that sits between the heel bone (calcaneus) and the two bones of the lower leg (tibia and fibula), playing a crucial role in transferring weight and pressure across the ankle joint. It facilitates movement and stability of the ankle, enabling actions such as walking, running, and jumping.
Talus: The talus is a bone located in the ankle joint, forming part of the talocrural joint. It is responsible for transmitting the weight of the body from the leg to the foot and plays a crucial role in the biomechanics of the lower limb.
Temporomandibular joint (TMJ): The temporomandibular joint is a hinge and sliding joint that connects the lower jaw (mandible) to the temporal bone of the skull, located just in front of each ear. It allows for movements necessary for chewing, talking, and yawning.
Tendons: Tendons are tough, fibrous connective tissues that connect muscle to bone, transmitting the force generated by muscle contraction to the skeleton and enabling body movements.
Tibia: The tibia is the larger and stronger of the two bones in the lower leg, located between the knee and the ankle. It is a crucial component of the skeletal system, playing a vital role in various aspects of anatomy and physiology.
Tibial collateral ligament: The tibial collateral ligament is a strong band of tissue that connects the femur (thigh bone) to the tibia (shin bone) on the inner side of the knee, providing stability to the medial aspect of the knee joint. It helps prevent excessive inward movement and rotation of the knee.
Ulna: The ulna is one of the two bones that make up the forearm, located on the little finger side. It is responsible for several important functions related to the skeletal system, joint anatomy, and upper limb movement.
Ulnar collateral ligament: The ulnar collateral ligament is a band of tough, fibrous tissue that connects the humerus (upper arm bone) to the ulna (one of the forearm bones) at the elbow joint, providing stability. It plays a crucial role in preventing the elbow from bending too far away from the body.
Ulnar nerve: The ulnar nerve is one of the major nerves of the arm, responsible for innervating (supplying with nerves) parts of the hand and facilitating muscle movement and sensation in the forearm and hand. It runs from the shoulder to the hand, passing through areas such as the inner elbow (often referred to when talking about hitting your "funny bone").
Zygapophysial joints: Zygapophysial joints, also known as facet joints, are synovial joints that connect the vertebrae in the spine. They facilitate back movements and provide stability by limiting excessive motion.