Transcript Training
JOINTS Chapter 8 Introduction Joints or articulations are sites where two or more bones meet Joints have two fundamental functions: – provide for skeletal mobility – hold the skeleton together Weakest parts of the skeleton, yet have a remarkable ability to resist the forces that tear them apart Classification of Joints Structural classification – focuses on the material binding the bones together and whether or not there is a joint cavity (fibrous, cartilaginous, synovial) Functional classification – based on the amount of movement allowed at the joint (synarthroses, amphiarthoroses, diarthroses) Functional Classification Synarthroses – Immovable joints Amphiarthroses – Slightly movable joints Diarthroses – Freely movable joints Structural Classification Fibrous – Joined by fibrous tissue Cartilaginous – Joined by cartilage Synovial – The bones are joined and surrounded by a joint cavity Note: – Structural classification is the system used in your text Summary of Joint Classes Fibrous joints – Suture – Syndesmoses – Gomphoses Cartilaginous joints – Synchondroses – Symphyses Synovial – Gliding, hinge, pivot, condyloid, saddle, and ball and socket Fibrous Joints In fibrous joints the bones are joined by fibrous tissue; no joint is present. The three types of fibrous joints are. . . Sutures – Dense fibrous connective tissue Syndesmosis – A cord or band of connective tissue Gomphosis – Peg-in-socket arrangement surrounded by fibrous tissue or peridontal ligament Suture Joint Occurs only between bones of the skull Wavy articulating bone edges interlock Junction is filled by connective tissue Rigid splices bind bones of the skull together tightly Syndesmosis Longer fibrous tissue occurs as a sheet or membrane Longer fibrous tissue permits the joint to “give” or flex True movement is not possible Gomphosis Fibrous tissue holds teeth in their sockets Teeth embedded in sockets of bone Anchored by fibers of periodontal ligament Cartilaginous Joints In cartilaginous joints, the articulating bones are united by cartilage, there is no joint cavity Synchondrosis – Hyaline cartilage unites the bones Symphysis – Fibrocartilage unites the bones Synchondroses Hyaline cartilage unites the bones Epiphyseal plates in growing children Provide for bone growth When growth ends all synchondroses become immovable Epipyseal Plate Synchrondroses Sternocostal joint between the manubrium and rib 1 is a immovable hyaline cartilage joint Symphyses Bone surfaces are covered with articular hyaline cartilage which is fused to a pad of fibrocartilage Fibrocartilage is resilient and acts as a shock absorber and permits limited movement Pubic Symphysis Synovial Joints In synovial joints articulating bones are located within a fluid containing joint cavity Synovial joints permit substantial range of motion All synovial joints have similar features Structures of Synovial Joint Articular cartilage – Hyaline cartilage on opposing bone surfaces Joint (synovial) cavity – Space filled with fluid Articular capsule – Capsule to confine fluid Synovial fluid – Fluid to lubricate joints Reinforcing ligaments – Maintain joint alignment Articular Cartilage Hyaline cartilage covers the bone surfaces Cartilage absorbs the compression placed on the joint Cartilage keeps the bone ends from being crushed Joint (synovial) cavity Joint spaces are unique to synovial joints Joint spaces are filled with synovial fluid Articular capsule The joint cavity is enclosed by a double layered articular capsule The external layer is a tough flexible fibrous capsule The inner synovial membrane Synovial Fluid Synovial fluid fills the entire joint Slippery fluid lubricates joint Weeping lubrication squeezes synovial fluid into and out of the cartilage nourishing the cells Synovial Fluid Reinforcing ligaments Ligaments reinforce joints Intrinsic ligaments reinforce capsule Extracapsular are outside capsule Intracapsular are inside capsule Extracapsular Ligament Intracapsular Ligament Features of Select Synovial Joints Certain synovial joints have additional structural features – Fatty pads cushion the knee and hip joints – Fibrocartilage articular discs separates articular surfaces (menisci) – Articular discs improve the fit between the articulating surfaces (knee, jaw) Bursae and Tendon Sheaths Bursae and tendon sheaths are closely associated with synovial joints Essentially sacs of lubricant Function as “ball bearings” to reduce friction between adjacent structures Reduces friction during joint activity Bursae Bursae are flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid Common at sites where ligaments, skin, muscles or tendons rub against a bone Bursae: Anomolies A bunion is an enlarged bursae at the base of the big toe False bursae may develop at any site where there is excessive motion Function similar to a true bursae Tendon Sheaths An elongated bursa that wraps completely around a tendon subjected to friction Tendon slides within this lubricated sleeve Common at sites where the tendon is subject to friction from other tendons or bone features Tendon Sheath Retinaculum Retinaculum Retinaculum function to confine tendons to a specific line of pull Muscle exerts a force around a skeletal feature Similar to a pulley or gear changing the angle of force exerted by a machine Factors Influencing Synovial Joint Stability The stability of a synovial joint depends on three factors . . . – The nature of the articular surfaces – The number and positioning of the ligaments – The tone and strength of the muscles acting upon the joint Articular Surfaces The surfaces determine what movements are possible at a joint, but play a minimal role in joint stability Many joints have shallow, “misfit” surfaces Larger surfaces or deeper sockets vastly improve stability Ball and socket joints are very stable because of their articular surfaces Articular Surfaces The knee is a hinge joint by classification The knee is an example of a joint that allows for “extra” movements The joint surfaces allow for some anterior posterior sliding, sliding, as well as a slight amount of rotation at full extension Ligaments Ligaments unite the bones of a joint Ligaments help to direct bone movement and prevent excessive or undesirable motion As a rule, the more ligaments a joint has the stronger it is Ligaments can stretch due to undue tension or trauma Ligaments can stretch only 6% of its length before it snaps Supporting Ligaments The supporting ligaments of the elbow allow flexion / extension and restrict movement in any other plane The Annular ligament allows for rotation of the head of the radius but restricts other movements Muscle Tone In most joints the muscles that act upon a joint are the most important stabilizing factor The tendons of the muscles keep the joint taunt and provide dynamic support Muscle tone is extremely important in reinforcing the shoulder and knee joint as well as the arches of the foot The articular capsule and the ligament have extensive sensory nerve endings providing reflexive contraction of supporting muscles Muscle Tone The knee is a joint that features movement over stability The knee is very dependent upon the muscles to provide dynamic stability to the joint while it moves Note: Rehab Movements Allowed by Synovial Joints Nonaxial Biaxial Multiaxial Gliding Movements Simplest type of joint movement Bone surface glides or slips over another similar surface Occur at the intercarpal and intertarsal joints as well as articular processes of vertebrae Flexion/Extension Flexion – A bending movement that decreases the angle of the joint Extension – A movement that increases the angle of the joint Flexion/Extension/Hyperextension Flexion – A bending movement that decreases the angle of the joint Extension – A movement that increases the angle of the joint Hyperextension – Bending beyond the upright position Flexion Flexion – A bending movement that decreases the angle of the joint and brings the two articulating bones closer together – Movement usually occurs in the sagittal plane Illustrated – Flexion of the arm – Flexion of the leg Extension Extension – A movement that increases the angle of the joint that moves the two articulating bones farther apart – Movement within the sagittal plane Illustrated – Extension of the leg and arm Dorsiflexion and Plantar Flexion Dorsiflexion – Lifting the foot so that its superior surface nears the shin Plantar flexion – Depressing the foot or pointing the toes downward Ab/Adduction/Circumduction Abduction – Movement of a limb away from midline or a spreading of the digits of the hand or foot Adduction – Movement of a limb toward midline or in the case of the digits toward the midline of the hand or foot Circumduction – Movement of a limb in a circle Rotation Rotation is the turning of a bone around its own long axis – Only movement possible between C1 & C2 – Common at the hip and shoulder joints – Medial or lateral is a function of whether rotation results in the anterior surface of the limb moving toward or away from the midline of the body Supination and Pronation Inversion and Eversion Protraction and Retraction Elevation and Depression Opposition Types of Synovial Joints Although all synovial joints have the same features they do not have a common structural plan Based on the shape of their articular surfaces there are six major categories of synovial joints – Plane, hinge, pivot, condyloid, saddle, and ball and socket Plane Joint A plane joint is the only example of a nonaxial joint Articular surfaces are essentially flat Allow only short slipping or gliding movements Plane Joints No rotation around an axis Examples – Intercarpals – Intertarsals – Vertebrae Plane joints Hinge Joints In hinge joints a cylindrical shaped projection of bone fits into a trough shaped surface of another bone Motion is within a single plane Joint components resemble that of a mechanical hinge Hinge Joints The elbow joint is an example of a hinge joint It allows for movement (flexion and extension) in only one plane Other example – Knee Pivot Joints The rounded end of a bone protrudes into a ring of bone and ligaments on another bone Only movement allowed is rotation of bone around long axis Pivot Joints An example is the joint between the atlas and axis, which allows your head to move side to side Another example is the proximal radioulnar joint, where the head of the radius rotates within the annular ligment Condyloid Joints In condyloid joints the oval articular surface of one bone fits into a complementary concavity in another Both articulating surfaces are oval shaped Condyloid Joints The biaxial joints permits all angular motions – flexion / extension – abduction adduction – Circumduction Metacarpophalangeal joints Saddle Joints Resemble condyloid joints, but allow greater freedom of movement Each surface has both a concave and a convex surface that fit together Each surface is shaped like a saddle Saddle Joints The best example of a saddle joint in the body are the carpometacarpal joints of the thumb Saddle Joint Ball and Socket Joint The spherical head of one bone articulates with the cuplike socket of another These joints are multiaxial and the most freely moving synovial joints Ball and Socket Joints Movements in all planes is allowed All axis and planes Examples – Shoulder – Hip Head of Femur fits Acetabulum Of pelvis Shoulder (Glenohumeral) Joint The shoulder joint has sacrificed stability for mobility Shoulder (Glenohumeral) Joint The glenoid labrum deepens the cavity The articular capsule is thin and loose to contribute to movement Shoulder (Glenohumeral) Joint Ligaments reinforce primarily the anterior aspect – Coracohumeral – Glenohumeral – Transverse humeral Shoulder (Glenohumeral) Joint Muscles crossing the joint provide most of the stability Long head of the biceps is the most important stabilizer Shoulder (Glenohumeral) Joint Four tendons of the rotator cuff encircle the joint, blend with the capsule – – – – Subscapularis Supraspinatus Infraspinatus Teres minor Shoulder Joint The joint lacks structural stability and shoulder dislocations are quire common Since the shoulder is weakest anteriorly and inferiorly, the humerous tends to dislocate forward and downward Hip Joint This ball and socket joint has good range of motion but the motion is limited by the deep socket and the joint ligaments Deep acetabulum is enhanced by circular acetabular labrum Ligamentum teres provides internal support to the joint Hip Joint This ball and socket joint has good range of motion but the motion is limited by the deep socket and the joint ligaments Deep acetabulum is enhanced by circular acetabular labrum Ligamentum teres provides internal to the joint Hip Joint Thick articular capsule encloses the joint Several strong ligaments support the joint – Iliofemoral, Pubofemoral, Ischiofemoral Ligaments are arranged in such a manner that they screw the head of the femur into the acetabulum when standing erect Elbow Joint The ulna and humerus provide a stable hinge joint that allow flexion and extension The Annular ligament anchors the head of the radius Supported laterally and medially by ligaments Knee Joint Largest and most complex joint Allows for flexion extension and some rotation C-shaped menisci deepen the tibial articular surface Menisci prevent side to side rocking and act a shock absorbers Knee Joint The intracapsular ligaments of the knee cruciates are located within the intercondylar notch Ligaments restrict anterior / posterior displacement Ligaments are named for their tibial attachment sites Knee Joint Posteriorly the joint is reinforced by the oblique popliteal ligament Gastrocnemius has two head that cross the joint posteriorly and provide dynamic stability Analysis of Knee Movements Weight bearing begins with the femur sliding posteriorly on the posterior aspect of the condyles During extension the femoral condyles travel forward until restricted by the anterior cruciate ligament Finally the lateral condyle stops before the medial spinning the joint into a locked position Analysis of Knee Movements When extending the knee as in kicking the same movements occur but in this case the tibia does the moving Analysis of Knee Injuries Knee is vulnerable to horizontal forces or high tension twisting movements These factors lead to – Isolated meniscus tears – Isolated medial collateral ligament tears – Isolated cruciate tears – Triad of O’Donahue Orthopedic Injuries to Joints Sprains - Ligament supporting a joint are stretched or torn Strains - Tendons or muscle fibers are stretched or torn Cartilage - Tear or fragmentation of the cartilaginous tissue Dislocation - Bones are forced out of their normal alignments at a joint Bursitis/Tendonitis - Inflammation caused by trauma or more frequently overuse Degenerative Conditions of Joints Arthritis – A general reference to over 100 different types of inflammatory or degenerative diseases of the joints Osteoarthritis – A degenerative disease related to the aging process (wear-and-tear arthritis) Rheumatoid Arthritis – A chronic inflammatory disorder alters the synovival membrane – Can lead to changes in articular cartilage and bone tissue of the joints Degenerative Conditions of Joints Gouty Arthritis – Abnormal amount of Uric acid contribute to the deposition of urate crystals in the soft tissues of joints – Lead to agonizingly painful joints – If untreated can lead to fusion and immobilization of the joint End of Chapter Chapter 8