What boney surfaces make up the radiohumeral joint?
head of the radius and capitulum of humerus
What boney surfaces make up the humeral ulnar joint?
trochlea of the humerus, trochlear notch of the ulna
What additional motion also occurs in elbow extension?
What is gunstock position?
gunstock = loss of the normal cubital valgus (13 deg), so arm is almost straight
What portion of the UCL in the elbow resists the first stages of valgus?
What ligament blends with the annular ligament?
T/F: The UCL has two parts.
false, UCL has 3 portions; RCL has 2 portions
What does the transverse portion of the UCL do, mainly?
stabilizes the elbow joint (the anterior and posterior portions resist more of the valgus force)
What ligament is there to prevent damage from falls on an outstretched hand?
ulnar portion of lateral collateral ligament; provides posteriolateral tension
What are the arthrokinematics of the elbow?
flex = anterior roll and slide extend = posterior roll and slide
T/F: The flexors are stretched in elbow flexion.
false, they’re compressed
What is the functional range for ADLs for elbow flexion/extension?
30-130 degrees (instead of 0-145 normally)
The interosseous membrane helps distribute what kind of forces? What is it not good at distributing?
- good for compressive forces (like falls) at radiocarpal jt
- bad for distractive forces
What do we have more range in, pronation or supination?
supination, by 10 degrees (85 vs 75)
What ligament supports the proximal radioulnar joint?
T/F: When we supinate, our GH joint automatically goes into external rotation.
true, a little bit of ER
- keep limb close to body when measuring supination so pt. can’t cheat with ER
What is the open-pack position for the humeroulnar joint?
70 degrees flexion, 10 degrees supination
What is the open-pack position for the distal radioulnar joint?
10 degrees supination (5 degrees is closed pack)
What arthrokinematics occur at the proximal radioulnar joint?
just spin, since the annular ligament is so tight
What arthrokinematics occur at the distal radioulnar joint?
radius moves on ulna (concave on convex)
- supination = dorsal roll and slide
- pronation = palmar roll and slide
What functional range is needed for ADLs for pronation/supination?
50 degrees either way
What is the triangular fibrocartilage complex? What’s it do?
TFCC = connects ulna to carpal bones, provides stability
- connects radius and ulna, and radius and carpal bones too
- consists of capsule, fibrocartilage disk, and ligaments
If the interosseus membrane isn’t distributing forces appropriately, what will happen to the joint?
decreased joint space, due to degeneration (on medial side?)
The certain elbow flexors being utilized are dependent on what?
elbow joint position (pronated, supinated, flexed)
What muscle is the workhorse of elbow flexion?
What muscle is the workhorse of elbow extension?
medial head of tricep (then lateral, then long)
At what angle is torque maximized for the bicep?
90 degrees elbow flexion
What elbow flexor is used in rapid movements for power?
What has the shortest moment arm of the elbow flexors? Longest?
shortest moment arm = pronator teres
longest moment arm = brachioradialis
T/F: Elbow and wrist flexors are both stronger than their opposing extensors.
What muscles help to lock the elbow should there be a C7 or up nerve root lesion?
anterior deltoid = horizontal adduction
pec major = adducts arm
• these keep arm close to body and locked for bed mobility since your arm extensors don’t work anymore
What is important to prevent in patients that have a C7 or above nerve root lesion?
flexion contracture, so they can still use the body-weight elbow lock maneuver to push up out of bed
What muscle is the synergist to elbow flexion?
- posterior deltoid -> it makes sure that GH flexion doesn’t occur, so optimal elbow flexion DOES occur
- exact opposite for elbow extension
What’s the best supinator of the forearm? Why?
bicep b/c of greater CSA; 2x stronger
What’s the best pronator? Why?
pronator quadratus because it is exactly perpendicular to axis of motion