Shoulder Instability

The shoulder is a ball-and-socket joint, where the head of the humerus (upper arm bone) fits into the glenoid (shoulder socket). Stability is maintained by a combination of ligaments, muscles, and the labrum—a ring of cartilage that deepens the socket. Shoulder instability occurs when the structures that support the shoulder joint are unable to maintain its normal position. When these stabilizing structures are weakened, stretched, or damaged, the shoulder can become unstable, leading to partial or complete dislocation.

There are three primary types of shoulder instability:

1. Traumatic shoulder instability: This typically occurs due to an injury or sudden impact, such as a fall, collision, or sports-related trauma. A forceful movement can cause the humeral head to dislocate from the socket, often tearing ligaments or the labrum in the process.
2. Non-traumatic shoulder instability: Some individuals have naturally loose ligaments (a condition known as ligamentous laxity), making them more susceptible to shoulder instability even without a major injury. This can lead to recurrent subluxations (partial dislocations) or discomfort during routine activities.
3. Multidirectional instability: This condition occurs when the shoulder is unstable in multiple directions without a clear history of trauma. It is often associated with generalized ligamentous laxity and is common in individuals who participate in activities requiring extreme shoulder mobility, such as swimming, gymnastics, or overhead throwing sports.

The symptoms of shoulder instability vary depending on the severity and type of instability. However, common signs include:

• Pain or discomfort: Patients often experience pain, especially with overhead movements, lifting, or reaching behind the back.
• Frequent subluxations (partial dislocation) or dislocations: A feeling that the shoulder “slips” out of place or dislocates entirely. Subluxations may cause brief moments of instability and discomfort, while full dislocations require medical intervention.
• Weakness or loss of function: Instability can lead to a lack of strength, making it difficult to perform daily tasks or sports activities.
• Clicking, catching, or popping sensations: Damage to the labrum or ligaments can cause unusual sounds or sensations in the shoulder during movement.
• Feeling of looseness or instability:  Patients often describe a sensation that their shoulder is “unstable” or may give out during certain movements.
• Numbness or tingling: In cases of severe dislocation, nerve compression may occur, leading to numbness, tingling, or weakness in the arm.

Several factors can contribute to shoulder instability, including:

• Traumatic injury: A fall, car accident, or sports injury can forcefully dislocate the shoulder, stretching or tearing the ligaments and labrum.
• Repetitive overhead movements: Athletes involved in sports like baseball, tennis, swimming, or volleyball place excessive strain on the shoulder, leading to progressive weakening of stabilizing structures.
• Genetic ligament laxity: Some individuals naturally have more flexible or loose ligaments, increasing their risk of instability without a specific injury.
• Previous shoulder dislocations: Once a shoulder has been dislocated, it is more prone to future instability due to residual ligament damage.
• Weak rotator cuff muscles: The rotator cuff plays a crucial role in stabilizing the shoulder. Weakness in these muscles can contribute to instability.
• Connective tissue disorders: These disorders can cause excessive joint laxity and instability in multiple joints, including the shoulder.

A thorough evaluation by an orthopedic specialist, such as Dr. David Gazzaniga at the Newport Orthopedic Institute, is essential for diagnosing shoulder instability. The diagnostic process typically includes:

Medical history and physical examination

• Dr. Gazzaniga will ask about the patient’s symptoms, history of dislocations or injuries, and activities that may contribute to instability.
• A physical exam will assess shoulder strength, range of motion, and stability. Specific tests, such as the Apprehension Test can help evaluate instability.

Imaging Studies

• X-rays: X-rays are useful to assess bone alignment and detect fractures or bone abnormalities.
• MRI: An MRI will provide detailed images of soft tissues, including the labrum, ligaments, and rotator cuff, to identify tears or damage.
• CT scan: In some cases, a CT scan may be used to get a more detailed view of bone structures and joint alignment.

Arthroscopic Examination

• In complex cases, a minimally invasive arthroscopic procedure may be performed to directly visualize the structures inside the shoulder joint and confirm the extent of instability.