a. Elbow Joint
The Ulna is the elbow joint bone of interest. Ulnas articulate
with humeral trochleas. Ulna's coranoid processes and humerus'
coranoid fossas limit elbow joints' flexion motion ranges. Ulna's
olecranon processes and humerus' olecranon fossas limit elbow
joints' extension motion ranges. Three-part ulnar collateral
ligaments medially secure ulnas' proximal ends to humerus' distal
surfaces. Anterior surfaces of ulnar olecranon processes have
trochlear ridges that slide in grooves of humerus' distal ends.
Anterior surfaces of ulnar olecranon processes have radial notche
on lateral sides where radial heads rest and rotate. Because
ulnas only move anteriorly and posteriorly, elbow joints only
flex and extend.
anterior surfaces have two bony landmarks, two tendon attachments
and two areas from which primary pitching muscles arise. Brachialis
tendons attach to coranoid processes. Flexor digitorum profundus
muscles arise from ulnas' proximal two-thirds. Pronator quadratus
muscles arise from lines on ulnas' distal one-quarters.
posterior surfaces have one bony landmark, two tendon attachments
and one area from which a primary pitching muscle arises. Triceps
brachiis' three heads combine into common tendons that attach
to ulnas' olecranon processes. Anconeus tendons attach to ulnas'
proximal one-fifths. Supinator muscles arise from medial surfaces
of ulnas' proximal ends.
b. Elbow Kinesiological
joint movements involve ulna movements relative to humeruses.
Kinesiologists generally include forearm joint actions with elbow
joint actions. However, muscles that attach to radiuses can only
indirectly influence ulna movements. Therefore, I separte forearm
and elbow joint actions. Ulnas only move toward or away from
humerus' anterior surfaces.
1. Extensions occur when elbow joint muscles contract to
move ulnas' anterior surfaces away from humerus' anterior surfaces.
Ulnas' olecranon processes and humerus' olecranon fossas move
2. Flexions occur when elbow joint muscles contract to move
the ulnas' anterior surfaces closer to humerus' anterior surfaces.
Ulnas' coranoid processes and humerus' coranoid fossas move closer
when humeruses rotate when ulnas flex or extend, then elbow joint
movements combine shoulder joint, elbow and wrist movements.
To explain these combinations, I created four more elbow joint
3. Lateral Extensions occur when elbow joint muscles contract
to move ulnas' anterior surfaces laterally away from humerus'
4. Medial Extensions occur when elbow joint muscles contract
to move ulnas' anterior surfaces medially away from humerus'
5. Lateral Flexions occur when elbow joint muscles contract
to move ulnas' anterior surfaces laterally closer to humerus'
6. Medial Flexions occur when elbow joint muscles contract
to move ulnas' anterior surfaces medially closer to humerus'
c. Elbow Joint
joint muscles attach to ulnas and directly influence elbow joint
muscles attach to ulnas' coranoid processes and to anterior surfaces
of humerus' distal one-halves. When brachialis muscles contract,
ulnas' coranoid processes and humerus' anterior surfaces move
closer together. Brachialis muscles flex, laterally flex and
medially flex ulnas. During decelerations, brachialis muscles
laterally flex elbow joints.
coranoid processes and humerus' coranoid fossas limit elbow joint
flexion motion ranges. Brachialis muscles attach to ulnas' coranoid
processes. Horizontal pitching arm actions cause forearms to
centripetally fly out horizontally. To prevent ulnas' olecranon
processes from colliding with humerus' olecranon fossas, brachialis
muscles centrifugally fight these fly out forces. Brachialis
muscles' coranoid processes physiologically adapt to cope with
these fly out forces. Ulnas' coranoid processes enlarge. Enlarged
ulna coranoid processes decrease elbow joint motion ranges.
muscles attach to lateral surfaces of ulnas' olecranon processes
and to posterior surfaces of humerus' lateral epicondyles. When
anconeus muscles contract, ulnas' olecranon processes and humerus'
posterior surfaces move closer together. Anconeus muscles extend,
laterally extend and medially extend ulnas. During forearm accelerations,
anconeus muscles medially extend elbow joints.
brachii I muscles attach to ulnas' olecranon processes and to
scapulas' infraglenoid fossas. When triceps brachii I muscles
contract, ulnas' olecranon processes and humerus' infraglenoid
fossas move closer together. Triceps brachii I muscles operate
across two joints, shoulder and elbow joints. Triceps brachii
I muscles indirectly extend shoulder joints and horizontally
extend humeruses. Triceps brachii I muscles extend ulnas. Two-joint
muscles cannot have both joints simultaneously changing joint
angles. Therefore, shoulder joints isoanglosly fix at single
joint angles when triceps brachii I muscles mioanglosly decrease
elbow joint angles. During forearm accelerations, triceps brachii
I muscles extend elbow joints.
curve pitching techniques place elbow joints at risk. If triceps
brachii I muscles incorrectly powerfully extend elbow joints,
ulnas' olecranon processes can slam into humerus' olecranon fossas.
Continued olecranon process/fossa slammings eventually injure
elbow joints. Olecranon process tips break off. Olecranon fossas
calcify. Extension elbow joint motion ranges decrease. Correct
curve pitching techniques move olecranon processes and fossas
lateral to elbow joint extensions.
brachii II muscles attach to ulnas' olecranon processes, distal
three-quarters of humerus' posterior surfaces and proximal one-thirds
of humerus' lateral surfaces. When triceps brachii II muscles
contract, humerus' olecranon processes and humerus' posterior/lateral
surfaces move closer together. Triceps brachii II muscles are
pure elbow joint muscles. Triceps brachii II muscles directly
extend ulnas. During forearm accelerations, triceps brachii II
muscles combine with medial epicondyle muscles to medially extend
joint muscles master complicated force application patterns or
suffer centrifugal acceleration injuries. Whereas clavicles and
humeruses cannot vary force application lengths, changing humerus/ulna
joint angles permit pitchers to apply straight-line forces to
Elbow Joint Actions
transitions, elbow joint muscles isoanglosly laterally flex ulnas
to approximately one hundred and fifty degree elbow angles. Lateral
flexions require humerus outward rotations and ulna flexions.
Humerus lateral epicondyle muscles laterally flex ulnas.
2. Upper Arm
upper arm accelerations, elbow joint muscles isoanglosly medially
flex ulnas to fix elbow joint angles. Humeruses powerfully drive
toward home plate. Medial flexions require humerus inward rotations
and ulna flexions. Humerus medial epicondyle muscles medially
forearm accelerations, elbow joint muscles powerfully mioanglosly
medially flex elbow joints. After humeruses start decelerating,
ulnas start driving toward home plates.
decelerations, elbow joint muscles plioanglosly laterally flex
elbow joints to stop ulnas' forward movements. Strong ligaments
prevent ulnas from moving away from humeruses during forearm
accelerations and slamming back into humeruses during decelerations.
However, radial heads do not have similar strong ligaments. Consequently,
radiuses do move away from humeruses and slam back into humerus
during forearm accelerations and decelerations.