Subacromial Impingement Syndrome

Written by Dr. Jason Ngan, DC

What is Subacromial Impingement Syndrome?

Subacromial impingement syndome (SAI aka swimmer’s shoulder) is a condition where shoulder tendons become inflamed and irritated. The acromion (top outer edge) of the scapula (shoulder blade) rubs against the shoulder tendon and ligaments. The humerus (upper arm bone) is surrounded by a group of muscles called the rotator cuff. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. The rotator cuff is responsible for stabilizing and movement of the shoulder. The acromion is located on top of the humerus. The small space between the acromion and humerus is called the subacromion. Due to its narrow size, the rotator cuff muscles that run through this area often gets injured.

What Causes Subacromial Impingement Syndrome?

SAI is caused by excessive use of the rotator cuff muscles. The tendons and ligaments in the subacromial area has little room to move. Constant movement and rubbing causes impingement in this area. The rotator cuff muscles start to get irritated and inflamed. The muscle most affected is the supraspinatus. Some common causes of SAI include:

  • Repetitive sports activity of the shoulder such as swimming

  • Old age (wear-and-tear)

  • Arthritis causes bony changes to this area

  • Weak rotator cuff allows humerus to move up causing impingement

  • Tight chest muscles (pectoralis minor attaches to coracoid process of scapula) pulls scapula down causing impingement

What are the Signs and Symptoms?

Symptoms can develop gradually and many patients will not realize it until months later.

  • Pain upon movement especially raising the arm forward or sideways

  • Pain and tenderness in the shoulder especially the front

  • Pain travels down the side of the arm

  • Pain upon side sleeping on the affected shoulder

    • Pain at night and affects sleep

  • Weakness in shoulder and arms

How is Subacromial Impingement Syndrome Diagnosed?

SAI is diagnosed with a thorough medical history, physical examination, orthopedic testing, x-ray diagnostic imaging, CT scan, MRI, and ultrasound.

  • Decreased range of motion

  • Diagnostic imaging such as x-ray, CT, and can check for signs of arthritis (bone spurs - extra bone growing out causing impingement)

  • MRI and ultrasound can check for tears of the rotator cuff tendons and bursitis (inflammation of the bursa)

What are the Treatment Options?

  • Chiropractic manipulation and mobilization

  • Soft tissue therapies

  • Gua-sha

  • Cupping

  • E-stim

  • Ultrasound

  • Ergonomic/postural counseling

  • Rehabilitative exercises and stretches

Other treatments that patients may seek (not provided at Ngan Chiropractic) include acupuncture, steroid injections, pain relief medication, and surgery if severe.  

References

  1. Akhtar, M., Karimi, H., Gilani, S.A. et al. The effectiveness of routine physiotherapy with and without neuromobilization on pain and functional disability in patients with shoulder impingement syndrome; a randomized control clinical trial. BMC Musculoskelet Disord 21, 770 (2020). https://doi.org/10.1186/s12891-020-03787-0

  2. Creech JA, Silver S. Shoulder Impingement Syndrome. [Updated 2022 Apr 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554518/

  3. Gebremariam L, Hay EM, van der Sande R, et al. Subacromial impingement syndrome—effectiveness of physiotherapy and manual therapy. British Journal of Sports Medicine 2014;48:1202-1208.

  4. Harrison, Alicia K. MD; Flatow, Evan L. MD. Subacromial Impingement Syndrome. American Academy of Orthopaedic Surgeon 19(11):p 701-708, November 2011.