Human Movement Science & Functional Anatomy of the:

Articularis Genu

by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS

Articularis Genu - http://spina.pro/i/anatomy/soedinenija-kostej/266.jpg

What's in a name:

• Articularis Genu - Originating from the latin roots "articularis" - pertaining to the joints, and "Genu" - pertaining to or relating to the knee (or knee shaped).

Articularis Genu:

• Origin: Anterior surface of distal part of the body of the femur (3, 11).
• Insertion: Proximal part of the suprapatellar bursa (an extension of the synovial cavity of the knee joint) and proximal anterior joint capsule of the knee (8, 11).
  • The articularis genu is a small muscle that may be blended with the vastus intermedius , but is usually distinct from it. This muscle lies deep to the vastus intermedius and rectus femoris  and inserts deep to the patella.
  • Unfortunately, one of my favorite anatomy texts, "Trail Guide to the Human Body (14)," did not mention palpation of this muscle, but I did find some great instructions on palpation at http://www.lastsite.ca/blog/chronic-knees/ . (Lots of great info on this blog) "To find the articularis genu, palpate the quadriceps at its distal attachment on the patella, gently investigate medially, with your index and 3rd finger under vastus medialis, and laterally with thumbs under vastus lateralis. Attempt to pinch or connect your fingers and thumbs together. This is where you will find a tight, dense tissue that has very little side-to-side and/or superior to inferior movement. This can be quite tender for the patient especially if this muscle has never been touched before." Although some will argue whether this is rectus femoris , vastus intermedius or articularis genu fibers I urge you to try the technique. I think you will find that as you palpate, the increased density of these tissues feels as if it originates underneath the patella and only extends a few inches (3 - 5") superior to the patella. This mass is too large to be a trigger point and too short to be a taut or over-active band in either the vastus intermedius or rectus femoris.
• Nerve: Branch of the nerve to to the vastus intermedius which arises from the femoral nerve via the lumbar plexus originating from nerve roots L2 and L3, sometimes L4.
• Action:
  • Knee: Draws the articular capsule superiorly.

Articularis Genu and the LE -http://www.unmc.edu/dissection/idg33hipknee.cfm

Integrated Function:

• Stabilization:
  • Increases tension in the anterior capsule during knee extension (eccentric flexion).
• Eccentrically Decelerates:
  • Potentially, eccentrically decelerates the inferior glide of the suprapatellar bursa during flexion to prevent entrapment.
• Synergists:
  • Although this muscle does not act on the tibia; and therefore, cannot contribute to knee extension force - this muscle is active during knee extension working synergistically with the rectus femoris and vastus muscles  ensuring the capsule and suprapatellar bursa is not impinged between the femur and patella during extension.
  • This muscle may be part of intricate system of muscles that tension and reinforce the capsule during motion, including the vastus lateralis, vastus medialis obliquus, tensor fascia latae via the iliotibial band, semimembranosus , gastrocnemius and popliteus.

Articularis Genu investing in the Suprapatellar Bursa - http://fitsweb.uchc.edu/student/selectives/knee-ankle/burs%20copy.JPG

Arthrokinematics:

• This muscle does not play a direct role in the arthrokinematics of the tibiofemoral or patellofemoral joints, but the function of this muscle is essential to maintaining optimal motion. As the knee extends this muscle ensures that the capsule and suprapatellar bursa are not impinged during end range extension and superior glide of the patella. Inflammation and effusion of the suprapatellar bursa is fairly common and may be noted post acute injury or surgical intervention, leading to a loss of terminal extension. But considering the chronic knee pain patient, it seems likely that dysfunction of the articularis genu could lead to impingement, inflammation and effusion of the suprapatellar bursa and may be a potential cause of pain. Could this be a too commonly forgotten muscle in our interventions for knee pain?

Note that this picture is the result of acute trauma, the inflammation associated with chronic knee pain is likely to present discreetly - http://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/Kneeffusion.JPG/781px-Kneeffusion.JPG

Fascial Integration:

My Fascial Hypothesis: Large fascial sheaths not only play a role in the transmission of mechanical force, but may also play a role in dictating the function of muscular synergies. This is likely caused by reducing or increasing tone of invested musculature via reflex arcs formed between mechanoreceptors imbedded in the connective tissue and the attached musculature. In this way my view of fascia differs slightly from noted expert on the subject Tom Myers. I think of these large fascial sheaths (specifically the thoracolumbar fascia, iliotibial band, and abdominal fascial sheath) as natures "mother board." A place for mechanical information to be communicated to the nervous system for more efficient recruitment of the muscular system. Despite having a slightly different philosophy it does not change the fact that fascia plays an important communicative role in the human body and we have Tom Myers to thank for his work.

Fascial Integration of the Articularis Genu:

• As mentioned above, this muscle may be part of intricate system of muscles that tension and reinforce the knee joint capsule during motion, including the vastus lateralis, vastus medialis obliquus,  tensor fascia latae  via the iliotibial band, semimembranosus  and popliteus . Although this type of relationship is different the fascial meridians discussed by Myers (6), or the myofascial synergies, discussed in my Core Subsystems  articles (originally described by Vleeming et. al. (15)), it is worth considering how investment in the joint capsule itself may affect recruitment strategies and activity. For example, would increased tension in the joint capsule stimulate receptor activity that results in reflexive facilitation of investing musculature, while effusion stimulates receptor activity that results in reflexive inhibition? Of course, understanding the affect of joint capsule receptors on investing musculature would apply to more than the just the articularis genu, and may be considered in relation to the rotator cuff, deep rotators of the hip , etc. I am personally eager to see these relationships investigated in future research. Further consideration, may implicate various synergistic or antagonist relationships between investing musculature. Outside of activation with the vastus muscles and rectus femoris , could increased activity of the tensor fascia latae  leading to increased tension of the iliotibial band and the imparted tension of the anterolateral joint capsule result in reflexive facilitation of the articularis genu?

Great diagram - http://classconnection.s3.amazonaws.com/720/flashcards/1137720/jpg/6711351818043487.jpg

Behavior in Postural Dysfunction:

Rather than being the "cause" of dysfunction or dyskinesis, it would seem the articularis genu becomes over-active in response to arthrokinematic dysfunction at the knee. Once over-active, the articularis genu may exacerbate or perpetuate dysfunction.

In Upper Body Dysfunction (UBD)  the articularis genu plays no significant role.

In Lumbo Pelvic Hip Complex Dysfunction (LPHCD) , Lower Leg Dysfunction (LLD) , and Sacroiliac Joint Dysfunction (SIJD)  the knee is subjected to deleterious forces resulting from either excessive valgus (Knees Bow In) or varus strain (Knees Bow Out) due to an inability to control tibiotalar, talarfemoral, or pelvofemoral alignment. In most cases, the inability to eccentrically decelerate femoral internal rotation and adduction, combined with excessive tibial external rotation and pronation of the forefoot results in the knee deflecting inward and excessive valgus strain. This dysfunctional pattern results in altered recruitment strategies that limit tibial anterior glide, especially of the lateral tibial plateau, resulting in arthrokinematic dyskinesis and increased tension on the anterior capsule. Further, the over-activity of the rectus femoris , tensor fasciae latae and vastus lateralis commonly seen in this dysfunctional pattern would alter patellar motion (superior and lateral glide with lateral rotation) and increase the likelihood of impinging the suprapatellar bursa.

It would seem that irritation of the suprapatellar bursa and anterior capsule in these dysfunctional patterns is the cause of over-activity and dysfunction of the articularis genu, although "over-flow" from over-active vastus lateralis , rectus femoris and vastus intermedius may also play a role. Once the articularis genu becomes over-active it is likely that the increased tone exacerbates irritation and inflammation of the suprapatellar bursa and joint capsule leading to pain, altered mechanics, and further dysfunction.

In short, this muscle tends to become over-active. Release, active release, and posterior to anterior tibia on femur mobilization should be incorporated to reduce activity and improve mechanics. It is my guess, that this is a commonly overlooked muscle in those individuals with chronic knee pain, and is worth considering when building corrective strategies and interventions. If the articularis genu is believed to be the source of pain, reversing your thinking and determining the dysfunctional pattern that has developed is essential for positive long-term outcomes. In essence, treating the articularis genu by itself is not going to fix anything, but adding it to a program designed to correct the LLD, LPHCD, or SIJD causing knee pain may lead to better outcomes.

Clinical Implications:

• Anterior, medial, or lateral knee pain
• Patellar tendonitis
• Suprapatellar Bursitis
• Chondromalacia Patella

Signs of Altered Length/Tension and Tone:

• Overhead Squat:
  • Subjective complaint of knee pain or soreness

Palpation of the Articularis Genu:

• For instructions on palpation head back to the top of the page - included with origin, insertion, action, etc. Trigger points are likely felt 2 - 4 inches directly superior to the patella, and may have some radiation to the patella or "underneath" the patella deep into the knee.

Exercises involving the Articularis Genu:

Rectus Femoris Self-administered Static Release (Note: I will create specific videos for this muscle in the future, but the technique is the same as below. The only difference is tender points will be investigated just superior to the patella)

Anterior Thigh Self-administered Active Release (Note: I will create specific videos for this muscle in the future, but the technique is the same as below. The only difference is tender points will be investigated just superior to the patella)

Progression for Posterior to Anterior Mobilization of the Tibia on the Femur (Note: This technique may be modified by using a thick "monster band placed below the knee to create a posterior to anterior force on the tibia. The client will work in end range with a goal of "locking" the knee while the band creates a posterior to anterior force.)

Progression for Posterior to Anterior Mobilization of the Tibia on the Femur (Note: In this technique the band is already placed appropriately for posterior to anterior mobilization (it is mentioned in the video). The client will work in end range with a goal of "locking" the knee while the band creates a posterior to anterior force.)

Bibliography:

1. Phillip Page, Clare Frank , Robert Lardner , Assessment and Treatment of Muscle Imbalance: The Janda Approach © 2010 Benchmark Physical Therapy, Inc., Clare C. Frank, and Robert Lardner
2. Dr. Mike Clark & Scott Lucette, “NASM Essentials of Corrective Exercise Training” © 2011 Lippincott Williams & Wilkins
3. Donald A. Neumann, “Kinesiology of the Musculoskeletal System: Foundations of Rehabilitation – 2nd Edition” © 2012 Mosby, Inc.
4. Michael A. Clark, Scott C. Lucett, NASM Essentials of Personal Training: 4th Edition, © 2011 Lippincott Williams and Wilkins
5. Leon Chaitow, Muscle Energy Techniques: Third Edition, © Elsevier 2007
6. Tom Myers, Anatomy Trains: Second Edition. © Elsevier Limited 2009
7. Shirley A Sahrmann, Diagnoses and Treatment of Movement Impairment Syndromes, © 2002 Mosby Inc.
8. David G. Simons, Janet Travell, Lois S. Simons, Travell & Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens
9. Cynthia C. Norkin, D. Joyce White, Measurement of Joint Motion: A Guide to Goniometry – Third Edition. © 2003 by F.A. Davis Company
10. Cynthia C. Norkin, Pamela K. Levangie, Joint Structure and Function: A Comprehensive Analysis: Fifth Edition © 2011 F.A. Davis Company
11. Florence Peterson Kendall, Elizabeth Kendall McCreary, Patricia Geise Provance, Mary McIntyre Rodgers, William Anthony Romani_, Muscles: Testing and Function with Posture and Pain: Fifth Edition © 2005 Lippincott Williams & Wilkins_
12. Brent Brookbush, Fitness or Fiction: The Truth About Diet and Exercise © 2011 Brent Brookbush - http://www.amazon.com/Fitness-Fiction-Truth-About-Exercise/dp/0615503012
13. Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004
14. Andrew Biel, Trail Guide to the Human Body: 4th Edition, © 2010
15. Vleeming, Andry, Movement, Stability & Lumbopelvic Pain: Integration of research and therapy, 2e (c) 2007 Elsevier Limited

© 2014 Brent Brookbush

Questions, comments, and criticisms are welcome and encouraged