Rotator cuff tear vs rotator cuff wear

"The rotator cuff is the only tendon structure situated between two bones. Compressed between the acromion and the humerus by every motion of the shoulder, it succumbs to the ravages of attrition long before most other tendons. In youth, it is thick, strong, and elastic and can be disrupted only by great force; after middle age, it has worn thin and often becomes so weak and brittle that it ruptures with ease." McLaughlin 1962


Detachment of the rotator cuff tendons from the greater tuberosity is often described as a rotator cuff tear. The word 'tear' suggests an acute process, such as tear in otherwise great blue jeans that can be easily repaired.

On the other hand, most cuff defects arise in tendons of suboptimal quality without an acute traumatic episode and may be better referred to as cuff wear, similar to defects in worn jeans that defy repair.

We emphasize the distinction in an article on rotator cuff failure in the New England Journal as well as in the text, The Shoulder, where we quote McLauhglin's admonition regarding 'rotten cloth to sew' in an Instructional Course Lecture: "The wise surgeon, realizing that he may find little but rotten cloth to sew, will operate only by necessity and make a carefully guarded prognosis. [There was complete agreement of the Panel on this point.]" See his 1962 article.

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Click here to see the new Rotator Cuff Book

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You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

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Rotator Cuff 8 - anatomy, MRI, Ultrasound, and surgery

Dear Readers
I'll be off line for a bit, but wanted to share a few rotator cuff illustrations with you before I go.
Here's what the rotator cuff looks like from within the joint.

Here's a cuff tear shown on ultrasound.

Here's a cuff tear shown on MRI

Here's a repairable rotator cuff tear.

Here's an irrepairable rotator cuff tear.

Here's a wild buck steelhead

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How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The ream and run procedure (see this link).

The total shoulder arthroplasty (see this link).

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).

Rotator Cuff 4 - Mechanisms of Tear, Factors Affecting Repair, "Impingement"

Initiation of Cuff Failure


Cuff fiber failure commonly results from the sudden application of eccentric loads, for example when the muscle attempts to resist a downward force on the arm

while the cuff seems to be better able to tolerate concentric loads, for example in a controlled lift away from the side. 

An anatomic factor predisposing to deep surface failure of the cuff insertion is internal abutment, where the corner of the glenoid contacts the deep aspect of the cuff at its tuberosity insertion 

This is most likely to be a problem for throwers who have stretched out their anterior capsule, allowing increased external rotation.



It is apparent that the most common form of cuff fiber failure, that which occurs on the articular surface of the cuff tendon, cannot be attributed to scuffing of the bursal surface by the acromion: so-called subacromial ‘impingement.’ In fact, the cuff insertion is well under the acromion at relatively small angles of elevation where it is protected from contact with the coracoacromial arch. Current evidence indicates that the most rotator cuff tears arise from tension overload and age-related attrition, rather than 'impingement'.

Readers might be interested in a recent review of the literature regarding the diagnosis of "impingement syndrome".

Factors Compromising Tendon Healing



Deep surface rotator cuff fiber failure exposes the defect to joint fluid. This joint fluid prevents the formation of a fibrin clot and, thus, healing is contravened.

Furthermore, tension at the edge of the cuff tear compromises the circulation to the margin of the tendon

For these reasons, left to their own devices, cuff defects tend to progress rather than healing. An optimal cuff repair surgery will bring healthy tendon into contact with vascularized bone and exclude joint fluid from the repair site. Subsequent posts will review the principles of surgical repair in some detail.


Factors Affecting Reparability

In considering the potential for surgically restoring a durable tendon insertion to bone, the surgeon needs to consider the quality of the tissue to be used in the repair. The ability of the cuff tendon tissue to withstand tensile loads is compromised by age, disuse, steroid injections, smoking, and poor general health. These predisposing factors can dispose the cuff tendons to fail with minimal force – essentially an atraumatic fiber failure. Cuff fibers that fail atraumatically may be so constitutionally weak that they cannot hold up even if repaired back to the bone. Thus, in chronic atraumatic cuff tears there is reason to consider a non-operative approach to improving shoulder function by rehabilitating the muscle–tendon units that remain intact.



Acute, traumatic cuff detachments that result from major force application are likely to be repairable

If acute traumatic cuff tears are not repaired promptly, the muscle may undergo intramuscular contracture, atrophy, and fatty degeneration and the tendon may become progressively reabsorbed. These degenerative changes compromise the opportunity for surgical repair. Thus, as with any other tendon avulsion from bone, time is of importance in the repair of acute tears of the rotator cuff. 

Loss of the rotator cuff subjects the superior glenoid to increased loads that can contribute to its erosion 

Progressive upward displacement of the humeral head produces secondary changes in the coracoacromial arch 

Once the humeral head has ascended so that its equator is above the residual cuff, contraction of the cuff muscles lock the humeral head in the superiorly displaced position

Chronic upwards displacement of the humeral head from cuff deficiency and superior glenoid erosion can result in cuff tear arthropathy,

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Use the "Search the Blog" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including: shoulder arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery.

See the countries from which our readers come on this post.

Rotator Cuff 3 - Patterns of tearing

In partial thickness cuff tears loss of some of the tendon fibers reduces the ability of the attached muscle fibers to deliver force to the bone.  This disruption typically starts on the deep surface of the cuff.

, but may also occur within the tendon

or on the bursal side.  

Partial tears may be accompanied by avulsion of a piece of the greater tuberosity

 A thinned tendon contains fewer fibers than one of normal thickness; thus, a muscle with a thinned tendon has lost the optimal attachment of its contractile elements and increasing load is placed on the remaining fibers

Partial tendon tears can also prevent effective use of the muscle by producing pain on muscle contraction.  In this respect a partial thickness cuff tear resembles a tennis elbow, a condition in which the extensor carpi radialis brevis is partially torn from the latter epicondyle.  Contraction of the muscle produces pain at the tendon attachment to bone.  This condition is also similar to partial thickness tears at the insertion of the Achilles and patellar tendons.  While these conditions are often thought to be inflammatory (“tendonitis”), the problem is actually mechanical. When a tendon is partially torn, there is disproportionate load on the fibers at the edge of the tear – like when a zipper is pulled open, or like a nylon stocking developing a run in it, or like a piece of paper that is partially torn – the load is on the connection adjacent to the tear.  This force concentration is sometimes referred to as the ‘notch’ phenomenon – a mechanism by which partial tears can propagate progressively

This progressive tendon tearing is often progressive, each step in the progression may be interpreted as episodes of ‘tendonitis’ until it is recognized that the problem is a cuff tear.

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How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The ream and run procedure (see this link).

The total shoulder arthroplasty (see this link).

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).

Rotator Cuff 1 - Overview

The rotator cuff has two main functions in the shoulder: (1) it stabilizes the humeral head in the glenoid socket and (2) it works with the deltoid and other shoulder muscles to help provide the strength necessary for the shoulder to do its work.


In this video, one can see how the supraspinatus tendon, the most commonly injured tendon of the rotator cuff, normally passes smoothly below the coracoacromial arch as the arm is lifted from the side in this cadaver demonstration.

For a short cut to an overview of the cuff and the spectrum of rotator cuff disease, see this page and the gallery on its right.

You may also like to see our recent review of rotator cuff failure from the New England Journal of Medicine.

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We'll take a step back and consider some of the principles of shoulder strength in depth.

When a muscle contracts, it approximates its effective origin and insertion with a force limited by its physiological cross sectional area. Muscles that have large cross sections, like the deltoid, can provide a larger maximal force than a muscle with a small cross section like the subclavius. The contractile elements within a muscle are connected to tendon fibers that connect to the bony origin and insertion. The tendon insertion is structured so that there is a smooth mechanical transition from flexible tendon to stiff bone.

This smooth transition enables the insertion to manage the repeated bending loads to which it is subject.

When the tissues providing this smooth transition degenerate they become stiff and weak so that the tendon insertion becomes increasingly vulnerable to failure.

The strength of a muscle is noted in terms of the torque it can generate. We recall that torque results when a force is exerted at a distance from a fixed center of rotation. The magnitude of the torque is the product of the length of the line connecting the center of rotation to the effective attachment of the muscle (the lever arm) and the magnitude of the force perpendicular to this line.

The effective points of attachment depend on the position of the arm and are not necessarily the anatomic insertions .

The weight of a dumbbell that can be held with the arm out to the side is determined by the sum of the products of the forces and their respective lever arms divided by the lever arm of the weight to be lifted.

Throughout this discussion, the lever arms have been described as the distance between the point of action of the muscle force and the center of rotation. In order for torques to be realized, the humerus must rotate around a stable center. This is why we have placed such emphasis on the mechanisms for centering of the head in the section on Stability. Without this precise centering, the effectiveness of the muscle contractions would be lost.

Muscles are also characterized by their excursion – the change in length over which they can provide force. In order to be effective throughout a range of motion, the centimeters of excursion of a muscle must match the product of the muscle’s lever arm in centimeters and the range of motion in degrees divided by the number of degrees in a radian.

So, while longer lever arms result in more torque per unit muscle force, they also require greater muscle excursion.

Muscles provide the maximal amount of force when operating close to the middle of their excursion with a drop off in maximal force as the muscle length approaches maximal extension or maximal contraction.

Muscles that have been chronically detached, as in long standing cuff tears, tend to lose their excursion. Even if they are reattached, the length over which they can exert an effective force is often diminished.

A special feature of the shoulder is that the powerful thoracoscapular muscles can position the entire glenohumeral joint along with the deltoid and the rotator cuff through a range of approximately 40 degrees of adduction/abduction

and 40 degrees of protraction/retraction

This ’portability’ of the glenohumeral joint enables the scapulohumeral muscles to carry out most shoulder functions in the mid-range of their excursion where they are the strongest. It is of note that the humeroscapular position is essentially the same for the knockout punch, the bench press, the point of racquet contact with the ball in the tennis serve, and the moment of release for the baseball pitch, even though the scapulothoracic positions are quite different.

One of the relatively unexplored facets of active shoulder strength is the requirement for muscular balance. In the knee, the muscles generate torques about a relatively fixed axis: that of flexion-extension. If the quadriceps pull is a bit off-center, the knee still extends. In the shoulder, no such fixed axis exists. In a specified position, each muscle creates a unique set of rotational moments. Imagine a rope attached to a sphere. The motion resulting from pulling on the rope depends on the orientation of the sphere as well as the direction of pull on the rope. If some of the resulting motion were undesired, it would need to be cancelled out by attaching another rope and pulling on it to resist the unwanted motion. So, for example, the anterior deltoid exerts moments in forward elevation, internal rotation, and cross-body movement.

If elevation without cross body movement is desired, the posterior deltoid must negate the cross body moment of the anterior deltoid.

Similarly, if elevation without rotation is desired, the cross-body and internal rotation moments of this muscle must be resisted by other muscles (such as the posterior deltoid and infraspinatus). These balancing activities take place at an additional energy cost. However, if the infraspinatus function is lacking, it is difficult to flex the arm without internal rotation.

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How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The ream and run procedure (see this link).

The total shoulder arthroplasty (see this link).

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).