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What is Thrower’s Exostosis of the Shoulder?

Thrower’s exostosis of the shoulder, which is also called a Bennett lesion of the shoulder, refers to the calcification in the posterior band of the inferior glenohumeral ligament, which is one of the ligaments that connect the upper arm bone to the shoulder socket. The lesion was first described in professional baseball pitchers by George E. Bennett in 1941. This is more prevalently seen in overhead throwing athletes such as baseball players. 

Causes of Thrower’s Exostosis of the Shoulder

A thrower’s exostosis of the shoulder occurs due to a traction injury during the deceleration phase of throwing the baseball. Repetitive minute trauma results in tearing of the ligament off of its glenoid insertion and subsequent reactive calcification. 
Thrower’s exostosis can also be associated with intra-articular pathology, especially posterior labral injury and under surface rotator cuff tears, as well as secondary to posterosuperior impingement.

Symptoms of Thrower’s Exostosis of the Shoulder

Thrower’s exostosis of the shoulder may result in the following signs and symptoms:

  • Posterior shoulder discomfort during the follow-through phase of the throwing cycle
  • Radiating pain down the posterior upper arm
  • Loss of strength in the shoulder and arm
  • Scapula pain when using the arm overhead
  • Snapping or popping sensation in the shoulder

Diagnosis of Thrower’s Exostosis of the Shoulder

A diagnosis of thrower’s exostosis of the shoulder is based on your symptoms, physical examination and imaging tests such as:

  • MRI scan
  • X ray
  • CT scan
  • Bone scan
  • Arthroscopy

Management of Thrower’s Exostosis of the Shoulder

Treatment options for thrower’s exostosis of the shoulder will vary based on the severity of the condition. It may include the following options:


  • Pain relievers to reduce pain
  • Steroid injections to reduce inflammation 
  • Physical therapy
  • Avoiding activities that exacerbate the condition


If conventional methods failed to treat thrower’s exostosis of the shoulder or it is associated with other complications, then your doctor might suggest surgical intervention which may be performed arthroscopically. The goal of surgery is to remove the bony outgrowth and any associated damaged tissues in order to improve range of motion and reduce pain. In some cases, an open surgery approach may be needed, where a larger incision is made to access the affected area. 

After the procedure, the patient will need to undergo a rehabilitation program that includes physical therapy to restore strength, flexibility, and range of motion in the affected shoulder. The recovery period may vary depending on the extent of the surgery and the patient's individual healing process, but typically ranges from several weeks to several months. 

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