A&P 1: Joint Detail

Temporomandibular joint (TMJ)

Articulation formed at point where head of the mandible articulates with temporal bone (articular tubercle of temporal bone anteriorly, mandibular fossa posteriorly)

Loose articular capsule surrounds joint; extensive range of motion

Articular disc: thick pad of fibrocartilage separates bones and extends horizontally to divide synovial cavity into 2 chambers

2 joints: temporal bone/disc + mandible/disc joints

Hinge for depression/elevation, glide for protraction (bite) and laterally (grind)

Sphenomandibular ligament

Thin band extends anteriorly and inferiorly from sphenoid to medial surface of mandibular ramus

Temperomandubular ligament

2 short bands extend inferiorly and posteriorly from articular tubercle of temporal bone to mandible

Sternoclavicular joint

Saddle joint between manubruim of sternum and sternal end of clavicle

Fibrocartilaginous articular disc partitions into 2 synovial cavities

Wide range of movement: depresseion, elevation, circumduction

Articular capsule fibers, extracapsular ligaments provide support/stability i.e. sternoclavicular, costoclavicular ligaments; clavicle fx before dislocation

Acromioclavicular Joint

Plane joint between acromion of scapula, lateral end of clavicle.

A fibrocartilaginous articular disc lies within the joint cavity between scapula and clavicle

Works with glenohumeral and sternoclavicular joints for upper limb range of motion

Supported by acromioclavicular and coracoclavicular ligament

Glenohumeral Joint

Ball-and-socket joint articulating head of humerus and scapula glenoid cavity; most mobile joint, prone to dislocation

Fibrocartilaginous glenoid labrum encircles & covers cavity with loose articular capsule attached to surgical neck of humerus

Weakly supported by coracoacromial, coracohumeral, glenohumeral ligaments

Rotator cuff muscles provide stability

Elbow joint

Hinge joint with humeroulnar and humeroradial joint enclosed in single thick articular capsule

Well supported by radial collateral (LCL) & ulnar collateral ligaments (MCL) and anular ligament (surround radius neck, binds proximal head to ulna)

Dislocations/subluxations are more common in children and teens

Hip/coxal joint

Ball-and-socket joint connecting head of femur and acetabulum of os coxae/acetabular labrum

Stable due to muscles, strong articular capsule, and ligaments: iliofemoral (y), ischiofemoral (spiral) and pubofemoral (triangle), plus ligamentum trens for blood supply

Retinacular fibers

Ligamentous fibers of the coxal articular capsule that fold over the neck of the femur and contain retinacular arteries to supply the femur hear

Knee joint

Largest, most complex diarthrosis; composed of tibiofemoral and patellofemoral joints

Capsule encloses medial, lateral, posterior regions; anterior covered by quadriceps femoris tendon with embedded patella

Fiblalar collateral ligament (LCL), tibial collateral ligament (MCL) for side reinforcement

Meidal & lateral meniscus pads on condyles of tibia for stability, cushioning, hyperadduction, hyperabduction

Anterior & posterior cruciate ligaments (x) to prevent hyperextension, hyperflexion

Can lock with tibial rotation

Unhappy triad

TCL, ACL, meniscus injury

Talocrural Joint

Highly modified hinge joint permitting dorsiflexion, plantar flexion at ankle

Single capsule with with tibia/talus and fibula/talus

To talus strong deltoid ligament binds tibia prevents overeversion, weaker lateral ligament binds fibula, prevents overinversion

Anterior/posterior tibiofiular ligaments bind tibia/fibula