What is the Rotator Cuff

In my practice I treat people with rotator cuff injuries frequently. My patients are often referred to me with “RC tear” or “rotator cuff tendinitis” and during the interview they will tell me they have a “rotator cup,” “rotary cuff,” or “rotary cup.” tear. One of my main focuses when treating my patients is education so they can better understand their condition. I will not get into differential diagnosis of rotator cuff complaints here because it’s beyond the scope of what I want to cover. Here I want to go through the basics of what the rotator cuff is and some risk factors. If you’re someone who has hurt their shoulder then please reach out to your doctor or physical therapist for a proper diagnosis – This is NOT medical advice.

Simple put, the rotator cuff is 4 muscles that act together to stabilize the shoulder joint during movement. These 4 muscles all arise from the scapula (shoulder blade) and insert on the humerus (upper arm bone) near the joint of the shoulder. Let’s go into a little more detail.

4 rotator cuff muscles

The 4 muscles that made of the rotator cuff are the Supraspinatus, Infraspinatus, Teres Minor, and Subscapularis. Often we call it the SITS muscles, to make it easy to remember. Each muscle has a different role in stabilizing or moving the shoulder. Let’s go through them

1. Supraspinatus
   The supraspinatus originates from the medial two thirds f the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It’s role is to abduct the arm (move it sideways, up-and-away from the body) for about the first 15° of movement before the deltoid starts to take over that movement. It also as pulls the head of the humerus (ball) medial into the glenoid cavity (socket) in order to prevent in from slipping inferiorly.
2. Infraspinatus
   The infraspinatus is the largest of the rotator cuff muscles. It orginates from the infraspinatus fossa of the scapula and attaches to the greater tubercle of the humerus. It is the essential external (lateral) rotator of the shoulder
3. Teres Minor
   The teres minor is a quite small muscle originating from the lateral border of the scapula (near the armpit) and inserts on the greater tubercle of the humerus. It works with the infraspinatus to externally rotate the shoulder, as well as slight adduction (bringing the arm toward the body).
4. Subscapularis
   The subscapularis is a fairly large muscle on the underside of the scapula. It originates for the subscapularis fossa and inserts on the lesser tubercle o the humerus. It internally (medially) rotates the shoulder as well as adductions.

Risks of RC tear

While anyone can experience a tear to the rotator cuff, there are some predisposing factors that may put you at a higher risk.

1. Age:
   As with any soft tissues, the muscles and tendons the the rotator cuff deteriorate over-time. The prevalence of rotator cuff tears begins to rise sharply after the age of about 55. some studies have shown that patients 60 years or above are twice as likely to sustain a large tear and nearly 60% of patients in their 80s have tears.
2. Gender:
   in younger individuals, gender does that appear to have an effect on incidence rate of rotator cuff tears. However, studies show that postmenopausal women are at increased risk for rotator cuff tears.
3. Smoking:
   A study in 2010 showed that out of the 375 rotator cuff tears found in their testing, 61.9% of the tears were in patients who smoked with a mean average of 23 years smoking at 1.25 packs per day.
4. Posture:
   This is actually an interesting one. a 2015 study that patients with poor posture had siginifcantly higher incidence of rotator cuff tears than those with a neutral posture. Poor posture was defined as either kypho-lordotic (exaggerated rounding upper back and low back), flat back (a loss of the natural curve of lumbar and thoracic spine), or sway back (an increase in posterior tilt of the pelvis and the trunk and increase upper back rounding)
5. Diabetes
   Diabetics have been shown to have a 47% higher risk of developing rotator cuff tears than those who do not have diabetes and have also been shown to be at higher risk for complications if they decide to undergo a rotator cuff repair.

I hope you found this informative. I may update this page from time to time. Feel free to comment with questions or if there is any information you would like me to add to the post.

References:

1. Abate M, Schiavone C, Di Carlo L, Salini V. Prevalence of and risk factors for asymptomatic rotator cuff tears in postmenopausal women. Menopause. 2014 Mar;21(3):275-80. doi: 10.1097/GME.0b013e31829638e3. PMID: 23760436.

2. Juneja P, Hubbard JB. Anatomy, Shoulder and Upper Limb, Arm Teres Minor Muscle. [Updated 2023 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513324/#

3. Karch M. Smith, Angela P. Presson, Chong Zhang, Joshua J. Horns, James M. Hotaling, Robert Z. Tashjian, Peter N. Chalmers,
Does diabetes mellitus predispose to both rotator cuff surgery and subsequent failure?, JSES International, Volume 5, Issue 4, 2021, Pages 636-641, ISSN 2666-6383, https://doi.org/10.1016/j.jseint.2021.03.002 (https://www.sciencedirect.com/science/article/pii/S2666638321000967)

4. Sambandam SN, Khanna V, Gul A, Mounasamy V. Rotator cuff tears: An evidence based approach. World J Orthop. 2015 Dec 18;6(11):902-18. doi: 10.5312/wjo.v6.i11.902. PMID: 26716086; PMCID: PMC4686437.