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Shoulder

Shoulder Instability

Shoulder anatomy

The shoulder is a ball and socket joint (glenohumeral joint) that consists of three bones – the collarbone (the clavicle), the shoulder blade (the scapula) which contains the glenoid cavity, and the head of the upper arm bone (the humerus).

Only 25% of the head of the humerus articulates in its socket forming a very shallow joint. This makes the shoulder one of the most mobile joints in the body but also makes it unstable. Nature has provided reinforcement with a structure called the labrum, a dense ring of cartilage that lines the shoulder socket and tightens the joint making it more stable. Additionally, the muscles and tendons around the shoulder and the rotator cuff are stabilizing structures that protect the joint and allow for a wide range of motion.

What is shoulder instability?

Shoulder instability is the inability to maintain the head of the upper arm bone in its socket because the muscles and ligaments have been torn or stretched and weakened.  When the shoulder repeatedly slips out of place it is called chronic instability.

What causes shoulder instability?

  • An overuse injury is where the joint stabilizers (muscles and ligaments) are stretched causing microtraumas in the tissues. This repetitive use injury is often found in athletes who participate in sports like baseball, gymnastics, swimming, tennis and volleyball, or labor that requires repetitive overhead motions.
  • A traumatic injury like a shoulder dislocation can damage the rotator cuff, tear the labrum, and stretch ligaments.
  • Shoulder subluxation where the shoulder only partially comes out of its socket can stretch the ligaments.
  • Hyperlaxity of the shoulder ligaments is naturally loose ligaments that cause multidirectional shoulder instability.
  • Failure of the soft tissue to heal from an injury can cause recurrent instability.

What are the symptoms of shoulder instability?

The main symptoms are pain, weakness, and a persistent sensation that the shoulder is loose. The pain may be sharp or dull and may bother you all day or only when you lift, throw, or move the shoulder joint. If your shoulder pain is due to a recent injury there may also be numbness and tingling. 

How is shoulder instability diagnosed?

Dr. Petrigliano will ask about your symptoms when they started and what causes them. He will review your medical history and conduct a physical exam. During the physical exam he will perform specific tests including testing the looseness (laxity) of your ligaments to evaluate your instability. Imaging studies will be ordered including X-rays or a CT scan to evaluate the bones and an MRI to view detailed images of the soft tissues including the ligaments and tendons in the shoulder joint.

Why choose Dr. Petrigliano?

Dr. Frank Petrigliano is an orthopaedic surgeon who was fellowship trained in sports medicine and shoulder surgery at the prestigious Hospital for Special Surgery where he provided care to athletes of all ages. He currently serves as the head team physician for the LA Kings hockey team and associate team physician for USC Athletics. Dr. Petrigliano is a renowned orthopaedic surgeon and researcher who employs state of the art treatments and procedures to get you back to your active life and back to sport. He always treats his patients with compassion and respect. Dr. Petrigliano is located in El Segundo California, and serves greater Los Angeles, Beverly Hills, the South Bay, and the Santa Clarita Valley. Contact Dr. Petrigliano to schedule a consultation today.

At a Glance

Dr. Frank Petrigliano

  • Associate Professor of Orthopaedic Surgery at USC
  • Chief of the Epstein Family Center for Sports Medicine
  • Team physician for the LA Kings and USC Athletics
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