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8.5 Selected Synovial Joints

• Synovial joints are diverse • All have general features, but some also have unique structural

features, abilities, and weaknesses• Five main synovial joints

– Knee– Shoulder– Elbow– Hip– Jaw

© 2016 Pearson Education, Inc.

Knee Joint

• Largest, most complex joint of body• Consists of three joints surrounded by single cavity

1. Femoropatellar joint • Plane joint• Allows gliding motion during knee flexion

2. Lateral joint and 3. Medial joint• Lateral and medial joints together are called tibiofemoral joint• Joint between femoral condyles and lateral and medial menisci of tibia• Hinge joint that allows flexion, extension, and some rotation when knee

partly flexed


Figure 8.7a The knee joint.

Femur

ArticularcapsulePosteriorcruciateligament

Lateral meniscus

Anteriorcruciateligament

Tibia

Tendon ofquadricepsfemorisSuprapatellarbursaPatellaSubcutaneousprepatellar bursa

Synovial cavityLateral meniscusInfrapatellar fat padDeep infrapatellarbursaPatellar ligament

Sagittal section through the right knee joint© 2016 Pearson Education, Inc.

Figure 8.7b The knee joint.

Anterior

Anteriorcruciateligament

Articularcartilageon medialtibialcondyle

Medialmeniscus

Posteriorcruciate ligament

Superior view of the right tibia in the knee joint,showing the menisci and cruciate ligaments

Articularcartilage onlateral tibialcondyle

Lateralmeniscus


Knee Joint (cont.)

• Joint capsule is thin and absent anteriorly• Anteriorly, quadriceps tendon gives rise to three broad ligaments

that run from patella to tibia– Medial and lateral patellar retinacula that flank the patellar

ligament• Doctors tap patellar ligament to test knee-jerk reflex

• At least 12 bursae associated with knee joint


Figure 8.7c The knee joint.

Quadricepsfemoris muscle

Tendon ofquadricepsfemoris musclePatella

LateralpatellarretinaculumFibularcollateralligament

Fibula

Medial patellarretinaculum

Tibial collateralligament

PatellarligamentTibia

Anterior view of right knee© 2016 Pearson Education, Inc.

Knee Joint (cont.)

• Capsular, extracapsular, or intracapsular ligaments act to stabilize knee joint

• Capsular and extracapsular ligaments help prevent hyperextension of knee– Fibular and tibial collateral ligaments: prevent rotation when

knee is extended– Oblique popliteal ligament: stabilizes posterior knee joint– Arcuate popliteal ligament: reinforces joint capsule posteriorly


Figure 8.7d The knee joint.

Tendon ofadductormagnus

Medial head ofgastrocnemiusmuscle

Popliteusmuscle (cut)

Tibialcollateralligament

Tendon ofsemimembranosusmuscle

Femur

Articular capsule

Oblique poplitealligament

Lateral head ofgastrocnemiusmuscle

BursaFibular collateralligamentArcuate poplitealligament

Tibia

Posterior view of the joint capsule, including ligaments© 2016 Pearson Education, Inc.

Knee Joint (cont.)

• Intracapsular ligaments reside within capsule, but outside synovial cavity

• Help to prevent anterior-posterior displacement– Anterior cruciate ligament (ACL)

• Attaches to anterior tibia• Prevents forward sliding of tibia and stops hyperextension of knee

– Posterior cruciate ligament• Attaches to posterior tibia• Prevents backward sliding of tibia and forward sliding of femur


Figure 8.7e The knee joint.

Posteriorcruciateligament

Fibularcollateralligament

MedialcondyleTibialcollateralligament

AnteriorcruciateligamentMedialmeniscus

Patellarligament

Patella

Quadricepstendon

Lateralcondyleof femur

Lateralmeniscus

Tibia

Fibula

Anterior view of flexed knee, showing thecruciate ligaments (articular capsuleremoved, and quadriceps tendon cut andreflected distally)


Figure 8.7f The knee joint.

Medial femoralcondyleAnterior cruciateligamentMedial meniscuson medial tibialcondyle

Patella

Photograph of an opened knee joint;view similar to (e)


Clinical – Homeostatic Imbalance 8.1

• Knee absorbs great amount of vertical force; however, it is vulnerable to horizontal blows– Common knee injuries involved the 3 C’s:

• Collateral ligaments• Cruciate ligaments• Cartilages (menisci)

– Lateral blows to extended knee can result in tears in tibial collateral ligament, medial meniscus, and anterior cruciate ligament

– Injuries affecting just ACL are common in runners who change direction, twisting ACL

– Surgery usually needed for repairs


Figure 8.8 The “unhappy triad:” ruptured ACL, ruptured tibial collateral ligament, and torn meniscus.

Lateral

Hockey puckPatella(outline)

Medial

Tibialcollateralligament(torn)

Medialmeniscus(torn)

Anteriorcruciateligament(torn)


Shoulder (Glenohumeral) Joint

• Most freely moving joint in body• Stability is sacrificed for freedom of movement• Ball-and-socket joint

– Large, hemispherical head of humerus fits in small, shallow glenoid cavity of scapula• Like a golf ball on a tee

• Articular capsule enclosing cavity is also thin and loose– Contributes to freedom of movement


Figure 8.9a The shoulder joint.

Acromion of scapulaCoracoacromial ligament

Subacromial bursaFibrous layer ofarticular capsule

Tendon sheath

Tendon of long headof biceps brachii muscle

Synovial cavity ofthe glenoid cavitycontaining synovialfluidArticular cartilage

Synovial membrane

Fibrous layer ofarticular capsule

Humerus

Frontal section through right shoulder joint


Figure 8.9b The shoulder joint.

Synovial cavityof the glenoidcavity containingsynovial fluid

Articular cartilage

Fibrous layer ofarticular capsule

Humerus

Cadaver photo corresponding to (a)


Shoulder (Glenohumeral) Joint (cont.)

• Glenoid labrum: fibrocartilaginous rim around glenoid cavity – Helps to add depth to shallow cavity– Cavity still only holds one-third of head of humerus

• Reinforcing ligaments– Primarily on anterior aspect– Coracohumeral ligament

• Helps support weight of upper limb– Three glenohumeral ligaments

• Strengthen anterior capsule, but are weak support


Figure 8.9c The shoulder joint.

AcromionCoracoacromial ligament

Subacromial bursa

Coracohumeralligament

Transverse humeralligament

Tendon sheathTendon of long headof biceps brachiimuscle

Coracoid processArticular capsulereinforced byglenohumeralligamentsSubscapularbursaTendon of thesubscapularismuscleScapula

Anterior view of right shoulder joint capsule


Figure 8.9d The shoulder joint.

Acromion

Coracoid process

Articular capsuleGlenoid cavityGlenoid labrum

Tendon of long headof biceps brachii muscleGlenohumeral ligaments

Tendon of thesubscapularis muscleScapula

Posterior Anterior

Lateral view of socket of right shoulder joint,humerus removed


Shoulder (Glenohumeral) Joint (cont.)

• Reinforcing muscle tendons contribute most to joint stability– Tendon of long head of biceps brachii muscle is “superstabilizer”

• Travels through intertubercular sulcus • Secures humerus to glenoid cavity

– Four rotator cuff tendons encircle the shoulder joint• Subscapularis• Supraspinatus• Infraspinatus• Teres minor


Figure 8.9c The shoulder joint.

AcromionCoracoacromial ligament

Subacromial bursa

Coracohumeralligament

Transverse humeralligament

Tendon sheathTendon of long headof biceps brachiimuscle

Coracoid processArticular capsulereinforced byglenohumeralligamentsSubscapularbursaTendon of thesubscapularismuscleScapula

Anterior view of right shoulder joint capsule


Figure 8.9d The shoulder joint.

Acromion

Coracoid process

Articular capsuleGlenoid cavityGlenoid labrum

Tendon of long headof biceps brachii muscleGlenohumeral ligaments

Tendon of thesubscapularis muscleScapula

Posterior Anterior

Lateral view of socket of right shoulder joint,humerus removed


Figure 8.9e The shoulder joint.

Acromion (cut)

Glenoid cavityof scapula

Glenoid labrum

Rotator cuffmuscles(cut)

Capsule ofshoulder joint(opened)

Head of humerus

Posterior view of an opened right shoulder joint


Elbow Joint

• Humerus articulates with radius and ulna• Hinge joint formed primarily from trochlear notch of ulna

articulating with trochlea of humerus– Allows for flexion and extension only

• Anular ligament surrounds head of radius• Two capsular ligaments restrict side-to-side movement

– Ulnar collateral ligament– Radial collateral ligament


Figure 8.10a The elbow joint.

ArticularcapsuleSynovialmembrane

Humerus

Fat pad

Tendon oftriceps muscle

Bursa

TrochleaArticular cartilageof the trochlearnotch

Median sagittal section through right elbow(lateral view)

Synovial cavityArticular cartilageCoronoid processTendon ofbrachialis muscleUlna


Figure 8.10b The elbow joint.

Humerus

Anularligament

Lateralepicondyle

Articularcapsule

RadialcollateralligamentOlecranon

Ulna

Lateral view of right elbow joint

Radius


Figure 8.10c The elbow joint.

Humerus

Anularligament

Medialepicondyle

RadiusArticularcapsule

Coronoidprocessof ulnaUlna

Ulnarcollateralligament

Cadaver photo of medial view of right elbow


Figure 8.10d The elbow joint.

ArticularcapsuleAnularligamentCoronoidprocess

MedialepicondyleUlnarcollateralligament

Humerus

Radius

Ulna

Medial view of right elbow


Hip (Coxal) Joint

• Ball-and-socket joint• Large, spherical head of the femur articulates with deep cup-

shaped acetabulum• Good range of motion, but limited by the deep socket

– Acetabular labrum: rim of fibrocartilage that enhances depth of socket (hip dislocations are rare)


Figure 8.11a The hip joint.

Articularcartilage

Acetabularlabrum

Femur

Hip (coxal) boneLigament of thehead of the femur(ligamentum teres)

Synovial cavityArticular capsule

Frontal section through the right hip joint


Figure 8.11b The hip joint.

Acetabularlabrum

SynovialmembraneLigament of thehead of the femur(ligamentum teres)

Head of femur

Articular capsule(cut)

Photo of the interior of the hip joint, lateral view


Hip (Coxal) Joint (cont.)

• Reinforcing ligaments include:– Iliofemoral ligament– Pubofemoral ligament– Ischiofemoral ligament– Ligament of head of femur (ligamentum teres)

• Slack during most hip movements, so not important in stabilizing• Does contain artery that supplies head of femur

• Greatest stability comes from deep ball-and-socket joint


Figure 8.11c The hip joint.

IschiumIliofemoralligamentIschiofemoralligament

Greatertrochanterof femur

Posterior view of right hip joint,capsule in place


Figure 8.11d The hip joint.

Anteriorinferior iliacspineGreatertrochanter

IliofemoralligamentPubofemoralligament

Anterior view of right hip joint, capsule in place


Temporomandibular Joint (TMJ)

• Jaw joint is a modified hinge joint• Mandibular condyle articulates with temporal bone

– Posterior temporal bone forms mandibular fossa, while anterior portion forms articular tubercle

• Articular capsule thickens into strong lateral ligament


Temporomandibular Joint (TMJ) (cont.)

• Two types of movement– Hinge: depression and elevation of mandible– Gliding: side-to-side (lateral excursion) grinding of teeth

• Most easily dislocated joint in the body


Figure 8.12a The temporomandibular (jaw) joint.

Mandibular fossaArticular tubercleZygomatic processInfratemporal fossa

Externalacousticmeatus

ArticularcapsuleRamus ofmandible

Lateralligament

Location of the joint in the skull© 2016 Pearson Education, Inc.

Figure 8.12b The temporomandibular (jaw) joint.

Articular discMandibularfossa

Articular tubercleSuperior jointcavity

Articularcapsule

Synovialmembranes

Condylarprocess ofmandible

Ramus ofmandible

Inferior jointcavity

Enlargement of a sagittal section through the joint© 2016 Pearson Education, Inc.

Figure 8.12c The temporomandibular (jaw) joint.

Superior view

Outline ofthe mandibularfossa

Lateral excursion: lateral (side-to-side) movements of the mandible



• Dislocation of TMJ is most common because of shallow socket of joint

• Almost always dislocates anteriorly, causing mouth to remain open– To realign, physician must push mandible back into place



• Symptoms: ear and face pain, tender muscles, popping sounds when opening mouth, joint stiffness

• Usually caused by grinding teeth, but can also be due to jaw trauma or poor occlusion of teeth– Treatment for grinding teeth includes bite plate – Relaxing jaw muscles helps


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