Today we will be looking at the diagnosis of impingement. Remember most shoulder impairments lie on a continuum of care, that is the shoulder pathology starts small with muscle imbalances, progresses secondary to biomechanical deficits, and eventually results in some type of structural damage.
Subacromial impingement begins as a result of of poor biomechanics or secondary to decrease subacromial space. Therefore, in the continuum of care it is a product of repetitive stress to the underlying tissue of the acromion process. The official definition of the subacromial impingement is the compression from the coraco-acromial arch and the humerous.
-Long head of the bicep
With that being said there are two types of impingements: Structural and functional.
Structural impingement-A reduction in the subacomial spaces secondary to boney growth, instability, calcification, boney structure etc.
The shape of the acromion process can play a large role in structural impingement. The acromion comes in 3 shapes or types:
Type I, flat
Type II, Curved
Type III, Hooked and most likely causing repetitive compression and irritation of the sub acromial structures
Functional impingement occurs because of bad mechanics, instability and poor posture that cause a decrease in space at a lower degree of shoulder movement.
Common causes include:
-IR humeral head
-Tight UT, Levator scap, Pec minor
-Weak Middle and lower trap
-Anterior Instability allows anterior translation of humeral head
-More in depth look at Scapula mechanics can be found on Scapulae dyskinesia page here.
Cluster Findings for Impingement
3 or greater + tests indicate +subacromial Impingement with a + LR of 2.93
To RULE OUT High Sensitivity
- A negative Hawkins Kennedy, Neer or horizontal adduction
Other differential diagnosis
-Drop arm sign for infraspinatus
-Lift of test for subscapularis
Stages of impingement
Edema and hemorrhage- less 25 years old
Fibrotic tendon changes- 25-40 year olds
Involves tendon rupture from increasing fibrotic tissues- greater then 50 y/o
Acute; rest, ice NSAIDS
Subacute chronic: Correct muscle imbalances, posture education