The rotator cuff (so named because it helps the shoulder to rotate) comprises the tendons of four muscles—the supraspinatus, infraspinatus, teres minor, and subscapularis—which surround the shoulder blade (scapula), wrap around the upper arm bone (humerus), and create a “cuff” that sucks the humeral head into the shoulder socket (glenoid fossa). It is one of the most important structures influencing the health of the shoulder because its individual muscles not only move the shoulder in specific directions, but because, as a unit, it acts as the major stabilizer of this very mobile joint.

Rotator cuff repair has become big business. From 1996 through 2006, the number of arthroscopic rotator cuff surgeries increased 600 percent, while the number of traditional open repair surgeries increased only 34 percent. Researchers speculate that surgeons are becoming more aggressive in treating rotator cuff tears, especially as outpatient surgery becomes more commonly available. Tears are only part of the picture, and other common rotator cuff problems include tendinitis, bursitis, trigger points, and everyday muscle aches, pains, and strains.

Rotator cuff anatomy

So why is the rotator cuff so vulnerable? Unlike the hip, the shoulder relies primarily on those four small muscles and their converging tendons to hold the humerus in place. In fact, the head of the humerus is larger than the glenoid fossa, so by its very structure it slides around much more in and over its socket than does the head of the femur. The head of the femur is also stabilized by the ligamentum teres femoris (also called the round ligament), which ties the femoral head into the acetabulum and provides another layer of protection for the hip that the shoulder lacks. Thus, some scientists consider the glenohumeral joint to be a muscular joint because its stability relies on muscle action.

Rotator Cuff  fig 1

Rotator Cuff Figure 1

The muscles of the rotator cuff are pictured in Figures 1 and 2. Three are located on the back (posterior) surface of the scapula and one on the anterior (front) surface that slides over the ribs:

-The supraspinatus fills the top part of the scapula, above the spine, and it abducts the shoulder.
-The infraspinatus fills the triangular portion below the spine, and it externally rotates the shoulder.
-The teres minor attaches on the lateral border near the axilla (armpit), and it externally rotates the shoulder.
-The subscapularis coats the entire front surface, closest to the ribs, and it internally rotates the shoulder.

The shoulder girdle itself comprises four major joints, three skeletal and one functional:

-The glenohumeral (GH) joint, the synovial ball-and-socket joint where the head of the humerus articulates with the glenoid fossa of the scapula.
-The acromioclavicular (AC) joint, the synovial plane joint where the scapula articulates with the clavicle (collarbone).
-The sternoclavicular (SC) joint, the synovial saddle joint where the clavicle articulates with the sternum (breastbone), which is the skeletal attachment of the shoulder girdle to the rest of the body; and
-The scapulocostal (ScC) joint, the functional joint formed by the anterior surface of the scapula sliding over the posterior surface of the ribcage.

Rotator Cuff Fig 2

Rotator Cuff Fig 2

These four joints function in concert to make the arm the most mobile limb in the human body, and because the shoulder girdle allows for incredible degrees of movement like flexion, abduction, extension, and rotation, it is prone to overuse and injury. Improper joint mechanics compound the problem; for example, if your shoulder is internally rotated and you attempt to abduct it more than 90º, you’ll end up pinching the supraspinatus tendon because the head of the humerus will crash into the acromion process due to the structure of the joint. The supraspinatus tendon is one of the most frequently torn tendons because it runs underneath the acromion process to attach to the humerus. When it is continually compressed by poor joint position, its already limited circulation is further degraded and its ability to repair becomes badly compromised. Hello, surgery.

But when the four rotator cuff muscles act together, the glenohumeral joint is in a much better position to perform movements in a stable, agile manner. One 2000 study found that the rotator cuff and biceps activated prior to movement, and Cook and Jones (2006) state that the “rotator cuff functions at a level we can’t consciously control,” citing grip as an important factor to activate the rotator cuff as a shoulder stabilizer.

Risk Factors for Injury and Recovery

Unfortunately, time is not on our side. The deterioration of the tendons appears to be inevitable as we age. Most people over the age of 50 already have damage to their rotator cuffs, and studies have found that more than half of people over age 65 likely have rotator cuff tears. As a 2010 study of 683 Japanese mountain villagers found, many of these tears are asymptomatic, so we may not even know that our shoulder structure is compromised.

Other risk factors for rotator cuff injury include having a high body-mass index, engaging in heavy labor, and being weak in shoulder abduction and external rotation.

Even when surgery is performed, if the rotator cuff muscles—especially the infraspinatus—are weak, the rotator cuff may not regain full function after the procedure. Gladstone and colleagues found that for patients whose infraspinatus and supraspinatus were weak and who had fatty infiltration of those tissues, flexion improved postsurgery but external rotation did not. Those patients were also more prone to reinjuring their rotator cuffs.

While I have not had shoulder surgery, I am squarely in the dysfunctional shoulder camp. Come back Friday for my favorite ways to rebalance the rotator cuff!


  1. Colvin, A.C., Egorova, N., Harrison, A.K., Moskowitz, A., & Flatow, E.L. (2012). National trends in rotator cuff repair. Journal of Bone and Joint Surgery 94:227–233. Retrieved from
  2. Cook, G., & Jones, B. (2006). Secrets of the Shoulder [DVD]. Functional Movement.
  3. David, G., Magarey, M.E., Jones, M.A., Dvir, Z. Türker, K.S., & Sharpe, M. (2000). EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint. Clinical Biomechanics 15(2):95–102.
  4. Davies, C. (2006). The frozen shoulder workbook. Oakland, CA: New Harbinger Publications.
  5. Gladstone, J.N., Bishop, J.Y., Lo, I.K., & Flatow, E.L. (2007). Fatty infiltration and atrophy of the rotator cuff do not improve after rotator cuff repair and correlate with poor functional outcome [Abstract]. American Journal of Sports Medicine 35(5):719–728. Retrieved from
  6. Johnson, J. (2006). Treat your own rotator cuff. Indianapolis, IN: Dog Ear Publishing.
  7. Knopf, K. (2010). Healthy shoulder handbook. Berkeley, CA: Ulysses Press.
  8. Miller, J. (2014). The roll model: A step-by-step guide to erase pain, improve mobility, and live better in your body. Las Vegas: Victory Belt.
  9. Muscolino, J. (2011). Kinesiology: The skeletal system and muscle function (2nd ed.). St. Louis, MO: Elsevier.
  10. Osti, L., Buda, M., & Del Buono, A. (2013). Fatty infiltration of the shoulder: Diagnosis and reversibility. Muscles, Ligaments, and Tendons Journal 3(4): 351-354. Retrieved from
  11. Peat, M. (1986). Functional anatomy of the shoulder complex. Physical Therapy 66, 1855–1865. Retrieved from
  12. Wendelboe, A.M., Hegmann, K.T., Gren, L.H., Alder, S.C., White, G.L., & Lyon, J.L. (2004). Associations between body-mass index and surgery for rotator cuff tendinitis. Journal of Bone and Joint Surgery 86(4):743-747.
  13. Yamaguchi, K. (2011, January). New guideline on rotator cuff problems. AAOS Now. American Association of Orthopaedic Surgeons. Retrieved from
  14. Yamamoto, A., Takagishi, K., Osawa, T., Yanagawa, T., Nakalima, D., Shitara, H., & Kobayashi, T. (2010). Prevalence and risk factors of a rotator cuff tear in the general population [Abstract]. Journal of Shoulder and Elbow Surgery 19(1):116–120. doi:10.1016/j.jse.2009.04.006


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Dawn Adams

Dawn has been practicing yoga since the mid-1990s. She took her first class at the Alameda Yoga Station in 1996 and has since studied under experienced teachers such as Sandy Blaine, JoAnn Lyons, and Donald Moyer. Dawn graduated from the Advanced Studies Program at the Yoga Room in Berkeley in 2009 and she continues to deepen her personal practice. Yoga has become an integral part of her life, especially because of its nurturing and centering aspects. Through practicing yoga, she has found that undoing is just as important as doing. In her teaching, she hopes to instill a sense of adventure and exploration of yoga, with a focus on finding balance and joy through practice. Most recently, Dawn found Yoga Tune Up and, fascinated by the functional approach to movement, completed the YTU Level 1 Certification. She is excited to share her unique approach to practice.

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Thanks for this rich and informative article! The mention of rotator cuff surgery as big business really hit home. My mom had her RC “repaired” but she has never gained full mobility and still experiences discomfort. I appreciate the Tune Up philosophy of knowledge as empowerment and self-care reducing the need for expensive health care.

Maureen Aitken

Such a well-prepared and thorough look at the rotator cuff muscles and I’m looking forward to the sequel!


Thank you Dawn for this article with highly dense information. It was very clear written and for me it is nice to have in short so much information all together. If you allow me: the first thought I had at risk factors for rotator cuff problems was bad posture! I see it a lot in my classes and I think that a bad posture keeps your shoulder in a position (like protraction combined with elevation) that is not ‘ideal’ for the movement of the shoulderjoint to begin with. Will be reading your other article about this subject!


Excellent article Dawn! I read through slowly and located each muscle and where it attaches, and thought through what movement it is involved in. You are so masterful in explaining anatomy. Thank you so much! I love the shoulder, and am always so amazed by how it’s able to function, and yet how it’s really a somewhat lousy “joint”. A muscle girdle much more more than ball and socket. Your explanation helped to reinforce this understanding for me. Looking forward to reading your next article on this subject.

Duygu (Dee) Ozkan

Thank you Dawn for this informative article! It is a great guidance for everyone to understand why we need to have the awareness of healthy, strong and in balance rotator cuff muscles by regular practice, especially against aging. Preventing injuries and surgeries by a little bit practice daily may change anyone’s life.

Elaine Jackson

Thank you for this well-researched and thorough article. The fact that we are not fully in conscious control of our rotator cuff activation makes a lot of sense to me (and I never knew this before). Particularly now that I’m in the over-50 camp and really struggling with rehabilitating a frozen shoulder. Looking forward to part 2.

Ernie M

Thanks for this overview of the anatomy of the rotator cuff. With all of these muscles and joints all working together to make various arm movements possible, it is no wonder that this is one of the more common issues and areas of imbalance we experience. My partner has been working through a number of shoulder issues on his dominant side including bicep tendonitis and AC joint misalignment having been a contractor for the past 30 years. It’s good to understand how the shoulder works and I look forward to reading the next article to see what we can do… Read more »

Katelynn Corman

Thank you for this highly knowledgeable article. My mother is suffering from shoulder pain and I’m trying to get as much information as possible to see if I can offer her some relief (and avoid surgery). I will be following up with your rotator cuff rebalance asap!

Nadine Maskallis

Thank you, Dawn, for this highly informative and comprehensive article as well as the extensive list of resources. As I am currently dealing with shoulder/supraspinatus dysfunction, it is a fantastic and practical guide for further research. I found the bit about “grip as an important factor to activate the rotator cuff as a shoulder stabilizer” especially fascinating.


Great informative article and thanks for posting it. I have seen lots of rotator cuff injuries among the students and friends and family. It is good to become aware of this problem and learn to prevent it.

Jeanette Johnsson

Thank you for detailing the rotator cuff muscles and their importance for shoulder health. I recently talked to a girl who has been practicing Downdog for years in a “hanging in the shoulder joint”-version+some internal rotation and might have injured her supraspinatus tendon from that.


This was very helpful and also well supported, thank you for taking the time to write this in such detail. By far, the shoulders tend to be what people complain the most about, and struggle the most with — in my 12 years of experience as a certified teacher. I myself have some shoulder instability on the left side due to several near-dislocations throughout my life (in fact it’s probably the other way around!) so this article will help me address this issue better.

Nina Watson

Thank you Dawn, this has been a very informative article. I have injured myself recently, in shoulder abduction and external rotation. Meaning lifting a heavy suitcase into a car. Your article has been very informative!

Kimberly Vickery

Concise, clear and informative. The glenohumeral is my favorite joint in the body. As a massage therapist, I see far too much dysfunction in this area and enjoy working with my clients to restore balance. I was not aware of the statistics related to age, thank you. Thank you also for all the references. Great article!!!

Michelle Tan

Thanks you for the details about the rotator cuff. It is very important for me to understand the anatomy of it as I practice downward facing dog in my yoga practice. By strengthening the rotator cuff muscles will help me to maintain the integrity of my glenohumeral joint, it will sure help when I practice downward facing dog.


Thanks for the article. Very clear informative explanation of Rotator’s Cuff working mechanism.


Thanks, Dawn for your article. Very clear explanation of Rotator’s Cuff working mechanism. Could help me to avoid long term of healing after Subscupularis tear injury


Thanks for the article. Very clear explonation about the mechanism of Rotator Cuff working.

Nadine Maskallis

Thank you, Dawn, for this detailed description of the intricate anatomy of the shoulder and the importance of rotator cuff stability for shoulder joint mobility. I find your description tremendously helpful in studying shoulder anatomy as well as understanding the correlation of muscle strength and joint mobility.

Natalie K.

Thank you Dawn. This article was super informative about the rotator cuff and it’s importance. To remind us why anatomy is so important in working with the shoulder joint.

François gosselin

Thank you for this very informative article. Most of my massage clients have weak external rotators as they work in front of a computer all day. Those who include strengthening are the ones to improve the most.


Thanks Dawn,
Many years ago I damaged my rotator cuff while doing dips at the gym; it still bothers me 30 years later.
I plan on using the roll model balls and YTU to improve the range of motion in my shoulder.


Yes! strengthening the rotator cuff muscles has helped me gain shoulder stability and no more pain in downdog and other shoulder weight bearing poses. thanks for the reference list!

Donna Burch

Very informative! This is the first blog I have read with references. I will definitely refer back to all of this.
Having injured my shoulder many years ago, and I was told it was a rotator cuff injury, now I wonder which muscle? They never identified it. And I was an athlete and our athletic trainer was a Physical Therapist.
Makes me wonder if he knew exactly which muscle or muscles.


Always in need of rotator issue reminders. I’d never really thought about how “rotator cuff functions at a level we can’t consciously control.” Also, a good reminder that grip helps to activate the rotator muscles and prepare the shoulder for movement.

Kyrin Hall

This article reminds us of the importance to ‘know’ our anatomy. Rotator Cuff Stability can be improved by externally rotating the shoulders, so when the shoulders abducted the head of the humerus will not be restricted by the acromion process nor pinch the supraspinatus tendon.

Alison Ahmoye Buchanan

This blog post is extremely educational! I am fascinated by all the work the muscles of the rotator cuff must do to stabilize this very mobile joint. Thank you for breaking down the directions of movement for the different muscles AND for also explaining all the joints within the shoulder girdle. This is information that everyone should learn – as it will help us all become more mindful of how we move, which will in turn reduce injuries from mundane actions. Thank you!


Wow! I had no idea that percentage of people have rotator cuff tears. And am completely unaware of fatty infiltration of tissues’ effect on surgery outcome. Looking forward to learning more about this & reading the Gladstone study.

Kris K

extremely informative, well done! i knew that the shoulder joint was quite unstable but when you highlighted the size of the head of the humerus compared to the area of the glenoid fossa as well as the lack of a supporting ligament (that the hip has) – i clearly now see why. several family members have rotator cuff issues and one is about to have surgery. being informed about our anatomy can aid as prevention of overuse and abuse. thanks for the article.


The title of your article seems to be a nice succinct expression of the traditional concept of sthira and sukha in yoga philosophy. I appreciate the poetic morn spin on it to help me to express myself with clients and students in the future.

Alexandra Dionne

Very interesting to know those differents statistics about surgery and risk to develop injury and pain in shoulders.
Thank you

Dana Healey

Your article makes me think about how I would describe why we focus so much on alignment in yoga. Someone might say why do we stack the joint and want correct posture before we do an exercise. As you said, “Improper joint mechanics compound the problem; for example, if your shoulder is internally rotated and you attempt to abduct it more than 90º, you’ll end up pinching the supraspinatus tendon because the head of the humerus will crash into the acromion process due to the structure of the joint”. Proper alignment puts less stress on the spine and joints, it… Read more »


Whoa! Wonderful information. I am focusing on the rotator cuff anatomy presently and this article was so informative. I’ll have to save this one and come back to it again and again for reference. Thanks also for the references. I love when they’re listed.


I really appreciate the articulation on the structure and function of the shoulder. I get a ton of athletes coming in with “rotator cuff injury” and they usually have no clue what that actually means. Im interested to see how people improve their shoulder mobility and range by keeping the rotator cuff muscles free of tension.

Christina Broome

Wow! Thank you for the in-depth article and helpful resources. Shoulder pain caused by instability is a familiar experience for me so I’m working with a Physical Therapist to strengthen the rotator cuff muscles and re-pattern my movement (even using therapy balls just off to one side of my spine while I pull and slowly extend my opposite arm). Thank you for the additional information.


Nancy Neuenhagen

Great article detailing the anatomy of the shoulder and rotator cuff. Many of the athletes I work with have shoulder issues most often related to the imbalance in strength of the internal and external rotators of the shoulder joint. Issues with strength imbalance in the rotator cuff combined with altered postural alignment of the scapula on the rib cage can lead to injuries in paddling sports. The addition of regular yoga exercises has resulted in fewer injuries over the past season.

Mindy Micheli

This is such a great article, I had never been so well versed on the intricacies of on the shoulder structure! Your knowledge and experience, as someone who has had “shoulder dysfunction”, has definitely benefitted those of us learning from you. Thank you Dawn.

Patti Breitbach Rashid

Interesting article! I look forward to our discussion and training tomorrow on DD in the Level 1 YTU teacher training. I have learned and taught DD in numerous ways.

Emilie Goldstein Mikulla

Thank you Dawn for this very clear explanation. I particularly love teaching students Dolpin Supinate as an alternative to Down Dog, or as a pose of its own, to allow students to propriocept what external rotation feels like. Another one of my favorite poses is also Dolphin with palms pressed together – not interlaced (as the cuffing sensation isn’t quite as clear. Such great poses to strengthen the rotator cuff – there are many – which is so so very important not only in the Yoga room, but in daily life.


Very interesting and useful article. On YTU level 1 teacher training we talked a lot about shoulders external rotation and flexion. But now i ve found out that external rotation is important for abduction as well. Knowledge is the power 🙂 It will really help to improve my practice.

Ann Moore

Dawn – Thank you for this great explination of the shoulder rotator girdle. Having had surgery I am working hard on my repair and it is a great reminder of what to work on and how the weaknesses can cause even more issues. I am on it!


Love love love. Thanks Dawn!

Christiane Parcigneau

Thank you for this indepth explanation of the shoulder joint and the functioning of the rotator cuff. I recently learned that I was incorrectly rotating my shoulders externally in downward dog (without pain). However, since I’ve changed my shoulder DOM to internal rotation, I’ve noticed a substantial improvement in my strength and stability in inverted poses. I’m grateful for having learned the safe way to support my body in a weight-bearing pose before a serious injury occurred!