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Joints & Joint Movements Human Anatomy Sonya Schuh-Huerta, Ph.D. Joints • Rigid elements of the skeleton meet at joints or articulations • Greek root “arthro” means joint • Structure of joints – Enables resistance to crushing, tearing, & other forces Classifications of Joints • Joints can be classified by function or structure • Functional classification based on amount of movement – Synarthroses immovable; common in axial skeleton – Amphiarthroses slightly movable; common in axial skeleton – Diarthroses freely movable; common in appendicular skeleton (all synovial joints) Classifications of Joints • Structural classification based on – Material that binds bones together – Presence or absence of a joint cavity – Structural classifications include: • Fibrous • Cartilaginous • Synovial Classifications of Joints Sutures – A Type of Fibrous Joint • Bones are tightly bound by a minimal amount of fibrous tissue • Only occur between the bones of the skull • Allow bone growth so the skull can expand with brain during childhood • Fibrous tissue ossifies in middle age – Synostoses = closed sutures Syndesmoses – A Type of Fibrous Joint • Bones are connected exclusively by ligaments • Amount of movement depends on length of fibers – Tibiofibular joint = immovable synarthrosis – Interosseous membrane between radius & ulna = freely movable diarthrosis Gomphoses – A Type of Fibrous Joint • Tooth in a socket • Connecting ligament the periodontal ligament Fibrous Joints (a) Suture (b) Syndesmosis (c) Gomphosis Joint held together with very short, interconnecting fibers, and bone edges interlock. Found only in the skull. Joint held together by a ligament. Fibrous tissue can vary in length but is longer than in sutures. Peg-in-socket fibrous joint. Periodontal ligament holds tooth in socket. Suture line Fibula Tibia Socket of alveolar process Root of tooth Dense fibrous connective tissue Ligament Periodontal ligament Cartilaginous Joints • Bones are united by cartilage • Lack a joint cavity • 2 types – Synchondroses – Symphyses Synchondroses • Hyaline cartilage unites bones – Epiphyseal plates – Joint between first rib & manubrium (a) Synchondroses Bones united by hyaline cartilage Sternum (manubrium) Epiphyseal plate (temporary hyaline cartilage joint) Joint between first rib and sternum (immovable) Symphyses • Fibrocartilage unites bones; resists tension & compression • Slightly movable joints that provide strength with flexibility – Intervertebral discs – Pubic symphysis • Hyaline cartilage present as articular cartilage Symphyses (b) Symphyses Bones united by fibrocartilage Body of vertebra Fibrocartilaginous intervertebral disc Hyaline cartilage Pubic symphysis Synovial Joints • Most movable type of joint!!! • All are diarthroses what does that mean? • Each contains a fluid-filled joint cavity General Structure of Synovial Joints • Articular cartilage – Ends of opposing bones are covered with hyaline cartilage – Absorbs compression • Joint cavity (= synovial cavity) – Unique to synovial joints – Cavity is a potential space that holds a small amount of synovial fluid General Structure of Synovial Joints • Articular capsule joint cavity is enclosed in a 2-layered capsule – Fibrous capsule dense irregular connective tissue, which strengthens joint – Synovial membrane loose connective tissue • Lines joint capsule & covers internal joint surfaces • Makes synovial fluid General Structure of Synovial Joints • Synovial fluid – A viscous fluid similar to raw egg white • A filtrate of blood – Arises from capillaries in synovial membrane • Contains glycoprotein molecules secreted by fibroblasts General Structure of Synovial Joints • Reinforcing ligaments – Often are thickened parts of the fibrous capsule – Sometimes are extracapsular ligaments located outside the capsule – Sometimes are intracapsular ligaments located internal to the capsule General Structure of Synovial Joints Ligament Joint cavity (contains synovial fluid) Articular (hyaline) cartilage Fibrous Articular capsule capsule Synovial membrane Periosteum (a) A typical synovial joint General Structure of Synovial Joints • Richly supplied with sensory nerves – Detect pain – Most monitor how much the capsule is being stretched General Structure of Synovial Joints • Have a rich blood supply – Most supply the synovial membrane – Extensive capillary beds produce basis of synovial fluid – Branches of several major nerves & blood vessels Synovial Joints with Articular Discs • Some synovial joints contain an articular disc – Temporomandibular joint & Knee joint – Occur in joints whose articulating bones have somewhat different shapes How Synovial Joints Function • Synovial joints lubricating devices • Friction could overheat & destroy joint tissue & bone ends • Are subjected to compressive forces • Fluid is squeezed out as opposing cartilages touch • Cartilages ride on the slippery film Bursae & Tendon Sheaths • Bursae & tendon sheaths are not synovial joints – Closed bags of lubricant – Reduce friction between body elements • Bursa = a flattened fibrous sac lined by a synovial membrane • Tendon sheath = an elongated bursa that wraps around a tendon Bursae & Tendon Sheaths Coracoacromial ligament Acromion of scapula Coracoacromial ligament Subacromial bursa Subacromial bursa Joint cavity containing synovial fluid Fibrous articular capsule Hyaline cartilage Tendon sheath Cavity in bursa containing synovial fluid Humerus resting Bursa rolls and lessens friction. Synovial membrane Tendon of long head of biceps brachii muscle Fibrous capsule Humerus (a) Frontal section through the right shoulder joint Humerus head rolls medially as arm abducts. Humerus moving (b) Enlargement of (a), showing how a bursa eliminates friction where a ligament (or other structure) would rub against a bone Movements Allowed by Synovial Joints • 3 basic types of movement – Gliding one bone across the surface of another – Angular movement movements change the angle between bones – Rotation movement around a bone's long axis Gliding Joints • Flat surfaces of two bones slip across each other • Gliding occurs between: – Carpals – Articular processes of vertebrae – Tarsals Gliding (a) Gliding movements at the wrist Angular Movements • Increase or decrease angle between bones • Movements involve: – Flexion & extension – Abduction & adduction – Circumduction Angular Movements Extension Flexion (b) Angular movements: flexion & extension of the neck Angular Movements Extension Flexion (c) Angular movements: flexion & extension of the trunk Angular Movements Flexion Extension Flexion Extension (d) Angular movements: flexion & extension at the shoulder and knee Angular Movements Abduction Adduction Circumduction (e) Angular movements: abduction, adduction, & circumduction of the upper limb at the shoulder PLAY Movement of the glenohumoral joint Rotation • Involves turning movement of a bone around its long axis • The only movement allowed between atlas & axis vertebrae • Occurs at the neck, shoulder, elbow, hip Rotation Rotation Lateral rotation Medial rotation (f) Rotation of the head, neck, & lower limb Special Movements • Elevation lifting a body part superiorly • Depression moving the elevated part inferiorly Elevation of mandible Depression of mandible Elevation Depression Special Movements • Protraction nonangular movement anteriorly • Retraction nonangular movement posteriorly Protraction of mandible Protraction Moving a body part in the anterior direction Retraction of mandible Retraction Moving a body part in the posterior direction Special Movements • Supination forearm rotates laterally, palm faces anteriorly • Pronation forearm rotates medially, palm faces posteriorly – Brings radius across the ulna Special Movements Pronation (radius rotates over ulna) Pronation (P) Rotating the forearm so the palm faces posteriorly Supination (radius and ulna are parallel) Supination (S) Rotating the forearm so the palm faces anteriorly Special Movements • Opposition thumb moves across the palm to touch the tips of other fingers Opposition Special Movements • Inversion & eversion – Special movements at the foot • Inversion turns sole medially • Eversion turns sole laterally Special Movements Inversion Inversion Turning the sole of the foot medially Eversion Eversion Turning the sole of the foot laterally Special Movements • Dorsiflexion & plantar flexion – Up-and-down movements of the foot – Dorsiflexion lifting the foot so its superior surface approaches the shin – Plantar flexion depressing the foot, elevating the heel (ballet toe point) Special Movements Dorsiflexion Plantar flexion Dorsiflexion Lifting the foot so its superior surface approaches the shin Plantar flexion Depressing the foot elevating the heel PLAY Eversion of Ankle joint (5a) Synovial Joints Classified by Shape • Plane joint – Articular surfaces are flat planes – Short gliding movements are allowed • Intertarsal & intercarpal joints • Movements are nonaxial • Gliding does not involve rotation around any axis Plane Joint Nonaxial movement Metacarpals Carpals (a) Plane joint Gliding Synovial Joints Classified by Shape • Hinge joints – Cylindrical end of one bone fits into a trough on another bone – Angular movement is allowed in one plane – Elbow, ankle, & joints between phalanges – Movement is uniaxial allows movement around one axis only Hinge Joint Uniaxial movement Humerus Medial/ lateral axis Ulna Flexion & extension (b) Hinge joint Synovial Joints Classified by Shape • Pivot joints – Classified as uniaxial – rotating bone only turns around its long axis – Examples • Proximal radioulnar joint • Joint between atlas & axis Pivot Joint Vertical axis Ulna Radius (c) Pivot joint Rotation Synovial Joints Classified by Shape • Condyloid joints – Allow moving bone to travel: • Side to side abduction-adduction • Back & forth flexion-extension – Classified as biaxial = movement occurs around 2 axes – Phalanges Condyloid Joint Biaxial movement Phalanges Anterior/ posterior axis Medial/ lateral axis Metacarpals Flexion & extension (d) Condyloid joint Adduction & abduction Synovial Joints Classified by Shape • Saddle joints – Each articular surface has concave & convex surfaces – Classified as biaxial joints – 1st carpometacarpal joint is a good example • Allows opposition of the thumb Saddle Joint Metacarpal 1 Medial/ lateral axis Trapezium (e) Saddle joint Anterior/ posterior axis Adduction and abduction Flexion and extension Synovial Joints Classified by Shape • Ball-and-socket joints – Spherical head of one bone fits into round socket of another – Classified as multiaxial allow movement in all axes • Shoulder & hip joints are examples Ball-and-Socket Joint Multiaxial movement Scapula Medial/lateral axis Anterior/posterior axis Vertical axis Humerus Flexion and extension (f) Ball-and-socket joint Adduction and abduction Rotation PLAY Movement of the glenohumeral joint (a) Factors Influencing Stability of Synovial Joints • Articular surfaces – Shapes of articulating surfaces determine movements possible Factors Influencing Stability of Synovial Joints • Ligaments – Capsules & ligaments prevent excessive motions – On the medial or inferior side of a joint prevent excessive abduction – Lateral or superiorly located resist adduction Factors Influencing Stability of Synovial Joints • Ligaments (cont…) – Anterior ligaments resist extension & lateral rotation – Posterior ligaments resist flexion & medial rotation • The more ligaments usually the stronger & more stable Factors Influencing Stability of Synovial Joints • Muscle tone – Helps stabilize joints by keeping tension on tendons – Is important in reinforcing: • Shoulder & knee joints • Supporting joints in arches of the foot Selected Joints Selected Synovial Joints • Temporomandibular Joint – Is a modified hinge joint – The head of the mandible articulates with the temporal bone – Lateral excursion is a side-to-side movement – 2 surfaces of the articular disc allow: • Hinge-like movement • Gliding of superior surface anteriorly The Temporomandibular Joint Mandibular fossa Articular tubercle Zygomatic process Infratemporal fossa Mandibular fossa Articular capsule External acoustic meatus Articular disc Articular tubercle Superior joint cavity Lateral ligament Articular capsule Ramus of mandible Synovial membranes Mandibular condyle Inferior joint cavity Ramus of mandible (a) Location of the joint in the skull (b) Enlargement of a sagittal section through the joint (arrows indicate movement in each part of the joint cavity) The Temporomandibular Joint Selected Synovial Joints • Shoulder (= Glenohumeral) joint – The most freely movable joint (lacks stability!) – Articular capsule is thin & loose – Muscle tendons contribute to joint stability The Shoulder Joint Acromion of scapula Coracoacromial ligament Subacromial bursa Fibrous articular capsule Glenoid labrum Synovial cavity of the glenoid cavity containing synovial fluid Hyaline cartilage Tendon sheath Synovial membrane Fibrous capsule Tendon of long head of biceps brachii muscle (a) Frontal section through right shoulder joint Humerus The Shoulder Joint Glenoid labrum Synovial cavity of the glenoid cavity containing synovial fluid Hyaline cartilage Fibrous capsule Humerus (b) Cadaver photo corresponding to (a) Glenohumeral Joint • The rotator cuff is made up of 4 muscles & their associated tendons – Supraspinatus – Infraspinatus – Teres minor – Subscapularis (= SITS muscles) • Rotator cuff injuries are common shoulder injuries The Shoulder Joint Acromion Coracoacromial ligament Subacromial bursa Coracohumeral ligament Greater tubercle of humerus Transverse humeral ligament Tendon sheath Tendon of long head of biceps brachii muscle (c) Anterior view of right shoulder joint capsule Coracoid process Articular capsule reinforced by glenohumeral ligaments Subscapular bursa Tendon of the subscapularis muscle Scapula The Shoulder Joint Acromion Coracoid process Articular capsule Glenoid cavity Glenoid labrum Tendon of long head of biceps brachii muscle Glenohumeral ligaments Posterior Anterior Tendon of the subscapularis muscle Scapula (d) Lateral view of socket of right shoulder joint, humerus removed Acromion (cut) Head of humerus Muscle of rotator cuff (cut) (e) Posterior view of an opened left shoulder joint Glenoid cavity of scapula Capsule of shoulder joint (opened) Selected Synovial Joints • Elbow joint – Allows flexion & extension – The humerus’ articulation with the trochlear notch of the ulna forms the hinge – Tendons of biceps & triceps brachii provide stability The Elbow Joint Articular capsule Synovial membrane Humerus Synovial cavity Articular cartilage Fat pad Tendon of triceps muscle Bursa Coronoid process Tendon of brachialis muscle Ulna Trochlea Articular cartilage of the trochlear notch (a) Mid-sagittal section through right elbow (lateral view) The Elbow Joint Humerus Annular ligament Lateral epicondyle Radius Articular capsule Radial collateral ligament Olecranon process (b) Lateral view of right elbow joint Ulna The Elbow Joint Articular capsule Annular ligament Coronoid process Radius Humerus Medial epicondyle Ulnar collateral ligament Ulna (d) Medial view of right elbow Wrist Joint • Stabilized by numerous ligaments • Composed of radiocarpal & intercarpal joint – Radiocarpal joint joint between the radius & proximal carpals (the scaphoid & lunate) • Allows for flexion, extension, adduction, abduction, & circumduction – Intercarpal joint joint between the proximal & distal rows of carpals • Allows for gliding movement Wrist Joint Radius Ulna Radiocarpal joint Lunate Scaphoid Triquetrum Pisiform Capitate Trapezoid Trapezium Thumb (a) Right wrist, anterior (palmar) view Hamate Radiocarpal joint Wrist Joint Radial collateral ligament Intercarpal joint (b) Wrist joints, coronal section Distal radioulnar joint Articular disc Ulnar collateral ligament Palmar radiocarpal ligament Wrist Joint Radius Ulna Radial collateral ligament Scaphoid Intercarpal ligaments Lunate Ulnar collateral ligament Pisiform Hamate Trapezium Capitate (c) Ligaments of the wrist, anterior (palmar) view Carpometacarpal ligaments Selected Synovial Joints • Hip joint – A ball-and-socket joint – Movements occur in all axes • Limited by ligaments & acetabulum – Head of femur articulates with acetabulum – Stability comes chiefly from acetabulum & capsular ligaments – Muscle tendons contribute somewhat to stability PLAY Movement of the hip joint The Hip Joint Coxal (hip) bone Articular cartilage Acetabular labrum Ligament of the head of the femur (ligamentum teres) Femur Synovial cavity Articular capsule (a) Frontal section through the right hip joint The Hip Joint Iliofemoral ligament Ischium Ischiofemoral ligament Greater trochanter of femur (c) Posterior view of right hip joint, capsule in place Anterior inferior iliac spine Iliofemoral ligament Pubofemoral ligament Greater trochanter (d) Anterior view of right hip joint, capsule in place Selected Synovial Joints • Knee joint – – – – – – The largest & most complex joint Primarily acts as a hinge joint Has some capacity for rotation when leg is flexed Structurally considered compound & bicondyloid 2 fibrocartilage menisci occur within the joint cavity Femoropatellar joint shares the joint cavity • Allows patella to glide across the distal femur Sagittal Section of Knee Joint Tendon of quadriceps femoris Femur Articular capsule Posterior cruciate ligament Lateral meniscus Anterior cruciate ligament Tibia Suprapatellar bursa Patella Subcutaneous prepatellar bursa Synovial cavity Lateral meniscus Infrapatellar fat pad Deep infrapatellar bursa Patellar ligament (a) Sagittal section through the right knee joint Superior View of Knee Joint Anterior Anterior cruciate ligament Articular cartilage on lateral tibial condyle Articular cartilage on medial tibial condyle Medial meniscus Lateral meniscus Posterior cruciate ligament (b) Superior view of the right tibia in the knee joint, showing the menisci and cruciate ligaments Anterior View of Knee Quadriceps femoris muscle Tendon of quadriceps femoris muscle Patella Lateral patellar retinaculum Fibular collateral ligament Medial patellar retinaculum Tibial collateral ligament Patellar ligament Fibula Tibia (c) Anterior view of right knee Knee Joint • Ligaments of the knee joint: – Become taut when knee is extended – These extracapsular & capsular ligaments are: • Fibular & tibial collateral ligaments • Oblique popliteal ligament • Arcuate popliteal ligament Knee Joint • Intracapsular ligaments – Cruciate ligaments • Cross each other like an “X” – Each cruciate ligament runs from the proximal tibia to the distal femur • Anterior cruciate ligament (ACL) • Posterior cruciate ligament (PCL) Anterior View of Flexed Knee Fibular collateral ligament Lateral condyle of femur Lateral meniscus Posterior cruciate ligament Medial condyle Tibial collateral ligament Anterior cruciate ligament Medial meniscus Medial femoral condyle Anterior cruciate ligament Tibia Patellar ligament Fibula Medial meniscus on medial tibial condyle Patella Quadriceps tendon (e) Anterior view of flexed knee, showing the cruciate ligaments (articular capsule removed, and quadriceps tendon cut and reflected distally) Patella (f) Photograph of an opened knee joint; view similar to (e) Knee Joint • Intracapsular ligaments – Cruciate ligaments prevent undesirable movements at the knee • Anterior cruciate ligament prevents anterior sliding of the tibia • Posterior cruciate ligament prevents forward sliding of the femur or backward displacement of the tibia Stabilizing function of cruciate ligaments 1 During movement of the knee the anterior 2 When the knee is fully extended, cruciate prevents anterior sliding of the tibia; the posterior cruciate prevents posterior sliding of the tibia. both cruciate ligaments are taut and the knee is locked. Quadriceps muscle Femur Anterior cruciate ligament Patella Medial condyle Anterior cruciate ligament Posterior cruciate ligament (a) Lateral meniscus Posterior cruciate ligament Tibia (b) The “Unhappy Triad” • Lateral blows to the knee can tear: – Tibial collateral ligament & medial meniscus – Anterior cruciate ligament – Are common sports injuries! Selected Synovial Joint • Ankle joint – A hinge joint between: • United distal ends of tibia & fibula • The talus of the foot – Allows the movements of: • Dorsiflexion & plantar flexion only The Ankle Joint – Medially & laterally stabilized by ligaments • Medial (deltoid) ligament • Lateral ligament – Inferior ends of tibia & fibula are joined by ligaments • Anterior & posterior tibiofibular ligaments The Ankle Joint Tibialis posterior muscle Tibia Calcaneal tendon Ankle (talocrural) joint Talocalcaneal ligament Talus Talonavicular joint Cuneonavicular joint Tarsometatarsal joint Metatarsal bone (II) Metatarsophalangeal joint Interphalangeal joint Calcaneus Subtalar joint Navicular bone Intermediate cuneiform bone (a) Cadaver photo of ankle and foot, sagittal section Tendon of flexor digitorum longus Ligaments of the Ankle Joint Tibia Talus Navicular Medial malleolus Medial (deltoid) ligament Sustentaculum tali 1st metatarsal (b) Right ankle, medial view Calcaneus Ligaments of the Ankle Joint Fibula Anterior tibiofibular ligament Tibia Posterior tibiofibular ligament Lateral malleolus Lateral ligament Anterior talofibular ligament Posterior talofibular ligament Calcaneofibular ligament Calcaneus Cuboid (c) Right ankle, lateral view Talus Metatarsals Disorders of Joints • Structure of joints makes them prone to traumatic stress • Function of joints makes them subject to friction and wear & tear • Affected by inflammatory & degenerative processes Joint Injuries • Torn cartilage common injury to meniscus of knee joint • Sprains ligaments of a reinforcing joint are stretched or torn • Dislocation occurs when the bones of a joint are forced out of alignment Inflammatory & Degenerative Conditions • Bursitis inflammation of a bursa due to injury or friction • Tendonitis inflammation of a tendon sheath Swollen bursa surrounding the knee Inflammatory & Degenerative Conditions • Arthritis describes over 100 kinds of jointdamaging diseases – Osteoarthritis most common type of “wear & tear” arthritis – Rheumatoid arthritis a chronic inflammatory disorder – Gouty arthritis (gout) uric acid build-up causes pain in joints • Lyme disease inflammatory disease often resulting in joint pain The Joints Throughout Life • Synovial joints develop from mesenchyme • By week 8 of fetal development, joints resemble adult joints – Outer region of mesenchyme becomes fibrous joint capsule – Inner region becomes the joint cavity The Joints Throughout Life • During youth injury may tear an epiphysis off a bone shaft; breaks near joints; dislocations • Advancing age osteoarthritis becomes more common • Exercise helps maintain joint health! Keeping Your Joints Healthy • Exercise is key – strengthens the muscles around the joints & stabilizes them; decreases injuries, joint disorders, wear-&-tear, etc. • Also good: proper nutrition, hydration, & vitamins/ supplements (glucosamine a good one) The journey of a mother & daughter Keeping Your Joints Healthy Questions…? What’s Next? Lab: Finish Bones & Joints Wed Lecture: Skeletal muscle Wed Lab: Selected Joints, Skeletal m. tissue & muscles
