What is Internal Impingement?

Internal impingement is a common but complex condition that usually affects athletes involved in overhead motion sports performing high stress and high velocity throwing actions repetitively. Internal impingement is also known as “The Throwers Shoulder” or the “Swimmer’s Shoulder”. It has a high occurrence rate in the younger athletic population. 

When the shoulder is put in extreme abduction and external rotation during overhead movements, either the supraspinatus or infraspinatus tendons get trapped between the humeral head and the posterior glenoid. This entrapment of the tendons causes them to get pinched between the structures surrounding them leading to internal impingement.

There are four stages involved in throwing: 

  1. Wind up 
  2. Cocking 
  3. Acceleration 
  4. Deceleration or follow-through 

The internal impingement occurs in the cocking phase. 

Internal impingement in itself is not an injury as it occurs to everyone while throwing. It becomes an injury when over time due to repetitive extreme overhead motion there is no period in between to heal.


Causes of Internal Impingement

Internal impingement is likely to be caused by the extreme stress put on the shoulder to perform the overhead motion. It can also be caused due to:

  • Soft tissue imbalances
  • Laxity or instability of glenohumeral 
  • Fragility in the long head of the biceps tendon
  • Glenoid labral tear
  • Tightness in the posterior capsule 


Symptoms of Internal Impingement 

As the condition is itself very common so are the symptoms. These include:

  • Sudden sharp pain in the shoulder while performing overhead motions
  • Tear in the rotator cuff and labrum  
  • Discomfort while sleeping due to pain 
  • Reduced ROM 
  • Damage to the rotator cuff leads to causing weakness in the shoulder 
  • Stiffness and swelling in the affected region of the shoulder 
  • Abnormal adaptation of the soft tissues


Diagnosis of Internal Impingement 

A thorough medical history of the patient is the first step in diagnosing the patient with internal impingement. The doctor will look into the activities involved and ask for the initial reason and location of the pain.

Diagnosing a patient with internal impingement can be a bit tricky because the symptoms are similar to that of any other shoulder pain and it is uncommon that the patient will have one specific mechanism of injury during the onset of pain.

The patient will often complain of pain in the posterior region of the shoulder that typically occurs in the cocking or throwing phase.

The doctor will carry out a physical examination to make an appropriate diagnosis in a patient with complex shoulder pain. Some complex shoulder pain generally originates from the cervical spine thus the first step is to assess it. The doctor should check the range of motion of the neck and perform Spurling’s test to assess for pain that radiates in the arm. Once the possibility of pain due to the cervical spine is ruled out, the attention will be directed to the glenohumeral joint. The doctor will make note of any asymmetry or abnormality in the muscles. 

Thus, the doctor will observe the patient while performing active ROM including forward flexion, abduction, and internal and external rotation at 0 to 90 degrees. 

Physical examination is followed by MRI scans as it is effective than X-ray in showing the internal impingement. A dye is injected into the joint space so that the tears in the rotator cuff or labrum can be detected. 

It is important that the MRI findings correlate with patients’ medical history and symptoms. 


Treatment for Internal Impingement

As with most shoulder conditions, nonsurgical treatments should be opted first. This includes:

  • Nonsteroidal anti-inflammatory drugs and injections as prescribed by the doctor help in decreasing inflammation and relieve pain. 
  • Rest is necessary to heal the shoulder and activities that may aggravate the pain should be avoided
  • Physical therapy aimed at restoring ROM and strengthening rotator cuff muscles and labrum should be performed under expert guidance. 
  • Sports/ job-specific training should be taken to improve performance, in this case, it is throwing

Typically, internal impingement is treatable with non-surgical methods alone. However, if nonsurgical methods do not provide satisfactory results the doctor will suggest surgery. 

Surgery is aimed at repairing the rotator cuff damage or labral damage. Controlled rebalancing of the capsule can also be performed.