The Elbow Complex: Part II

In Part 1, the general anatomy of the elbow was discussed.  As previously mentioned, this elbowkinheaderseries on the elbow is meant to provide any individual dealing with nagging elbow discomfort the knowledge and tools they need to help decrease pain and improve function.

In part two, the basic kinesiology of the elbow will be reviewed, to allow you to better understand the dynamics of the elbow, and encourage you to understand the reason you may be having pain and dysfunction.   In this section, we will discuss normal movement.

Part 3 will dive into common injuries and the associated movement impairments.

OSTEOKINEMATICS

Osteokinematics describes the motion of the bones during human movement at any particular joint.  For the elbow complex, we will focus on the three joints of the elbow: Humeroulnar joint, Humeroradial joint, and Proximal Radioulnar Joint (PRUJ).


HUMEROULNAR AND HUMERORADIAL JOINTS

hr-hu-jt
The elbow joint articulation.

The humeroulnar joint is the true hinge joint of the elbow.  It allows for flexion and extension of the forearm in relation to the humerus.  Normal range of motion is anywhere from 10 degrees of hyperextension, to in some people close to 160 degrees of flexion.

 

This makes for a substantial amount of motion, allowing us to bring food to our mouths, touch the back of our necks, and tuck in our shirts in the back.

The humeroradial joint is the articulation between the head of the radius, and the capitulum of the humerus.  This acts much like a hinge joint, moving into both flexion and extension like the humeroulnar joint.

 


PROXIMAL RADIOULNAR JOINT

PRUJ doorknob.png
The PRUJ works much like a “doorknob,” spinning on its axis to allow for forearm pronation and supination.

This joint is considered a “pivot” joint, as it allows the forearm to move into supination and pronation (palm up and palm down).  It is the articulation of the radius and ulnar, near the elbow.  To better picture the joint mechanics, picture a standard door knob.  Supination (90 degrees) and pronation (70 degrees) allows for a total arc of over 150 degrees of motion.  This, coupled with the humeroulnar joint, allows for increased functionality of our wrist and hand.

 

 


ARTHROKINEMATICS

Arthrokinematics describes the motion that is occurring within the joint during normal movement.  We typically describe this as a direction of a roll or glide, of one bone on the other.  For instance in the elbow, the radius rolls and glides anterior on the humerus, during elbow flexion.  The opposite is true for extension (posterior roll and glide). This is due to the concave surface of the radial head (fovea) on the convex surface of the humerus (capitulum).   We call this the concave rule, and it describes what accessory motions are occurring within the joint during normal movement.

 

In the convex rule, the joint kinematics are different, due to the nature of the joint surfaces.  We see the convex rule in the proximal radioulnar joint.  Here, the convex radial head sits in the convex radial notch of the ulna.  When moving into supination, the radius seems to move posterior in relation to the ulna (osteokinematic).  But when we analyze the actual joint kinematics, what is actually occurring is a posterior roll, and an anterior glide of the radius on the ulna.  Opposite is true for pronation (anterior roll, posterior glide).

 


FASCIA’S ROLE AT THE ELBOW

Because of the dense muscular attachments to the bones of the elbow, the fascia plays an important role in maintaining a happy and healthy elbow joint.  Fascia is connective tissue that helps keep anatomical structures in approximation, as well as provides proprioception, nociception (pain response), and mechanoreception, through its dense neural innervation.  For more information about fascia, click here, to read more about AnatomyTrains discussion on the importance of healthy fascia.  Below, Thomas Myers of AnatomyTrains discusses fascia.

   In the elbow, we see overuse injuries typically at the teno-osseous junctions, which is where bone and tendon meet.  This is most recognized in cases such as medial and lateral epicondylalgia, where the common extensor tendon mass, or common flexor-pronator mass, sustains microtears from continuous repetitive stress.  Think of an electrician turning a screw driver all day, the duty cycle will eventually run past its capacity, and pain and dysfunction will ensue.  Same can be said for a CrossFitter, whose workout may flexor-pronator-fasciaconsists of pull-ups, hang cleans, and handstand walks.  In this case, the flexor-pronator mass is tugging continuously on the medial epicondyle through repetitive active contraction, as well as passive stretch during wrist extension.

   The fascia that surrounds these structures, or compartments of the elbow, can become “sticky” and lose its ability to slide and glide appropriately.  Without proper maintenance, you will likely develop muscular trigger points due to the hypomobility of your tissues, causing pain due to the high level of neural innervation.  Same is true for the common tendinous insertions in the elbow.  Medial and lateral epicondylitis can be improved through treatment to the fascia.


WHO CARES ABOUT THIS STUFF?

For someone with nagging elbow pain, you should.

So why does this matter?  Well, if you’re dealing with a “sticky” or “stiff” joint, knowing the normal osteokinematics, arthrokinematics, and fascial connections can cue you in on how to manage your symptoms and improve your function.  Through hands on techniques, or using different mobility tools, we can hone in and assist normal arthrokinematics to improve osteokinematic range of motion and function.

Knowing the basic joint mechanics of the elbow complex can help you determine how to manage your symptoms.  In this section, we have scratched the surface of elbow kinesiology.  For more information or to clarify things, I encourage you to contact me.  For serious or chronic injuries, please consult with your physical therapist, movement specialist, or physician.

Part 3 will discuss some of the common injuries of the elbow, with Part 4 wrapping up this series with treatment ideas and options to keep you mobile and pain free.

 

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