Shoulder Instability: Causes, Symptoms & Non-Surgical Options

Medically Reviewed By:

Dr. Chaz Fausel, MD

Dr. Chaz Fausel is a Denver-based interventional orthopedics specialist and Regenexx educator, trained at Emory and the Centeno-Schultz Clinic.

Shoulder instability may disrupt joint function and interfere with daily activities. The extent of instability and the type of damage involved often influence the recovery timeline and available treatment approaches. 

Accurately measuring the degree of instability helps determine the most appropriate treatment path. While imaging tools like MRI can help detect structural damage, they provide only static images. Since shoulder instability involves excessive joint motion, static imaging may not provide a complete assessment.

Stress ultrasound imaging may offer a more dynamic way to assess instability in real time. By evaluating how the joint moves under load, physicians in the licensed Regenexx network can better understand the degree of instability.

Before exploring how ultrasound-guided imaging may assist with diagnosis, it’s helpful to understand shoulder anatomy and the underlying causes of instability.

Understanding Shoulder Anatomy 

The shoulder is one of the most mobile joints in the body. It is formed by the connection of three bones: the upper arm bone (humerus), the shoulder blade (scapula), and the collarbone (clavicle). Together, these bones create a ball-and-socket joint that allows for a wide range of motion in multiple directions.

A network of soft tissues, including ligaments, the joint capsule, and surrounding muscles, maintains joint stability. Ligaments connect bones and help prevent excessive movement. The joint capsule is a flexible envelope of connective tissue surrounding the joint, helping maintain proper alignment during motion. 

Muscles around the shoulder, particularly the rotator cuff, also play a vital role in keeping the joint centered and supported during activity.

The ligaments that help stabilize the shoulder may become stretched or loosened over time. Contributing factors can include a history of shoulder dislocation, gradual joint degeneration with age, structural differences in joint anatomy, or general wear and tear from repetitive use.

What Is Shoulder Instability?

Shoulder instability refers to a condition in which the structures that usually help keep the joint in place become too loose, allowing the joint to move excessively. Ligaments, which connect bones and provide structural support, play a central role in stabilizing the shoulder. Over time, these ligaments may stretch or weaken, reducing their ability to keep the joint aligned.

Several factors may contribute to this loss of ligament tension, including a history of traumatic dislocation, age-related changes in the joint, anatomical variations, connective tissue disease, or repetitive strain on the shoulder. When the supporting structures can no longer maintain the joint’s normal position during movement, instability can develop.

Shoulder instability is typically defined by excessive joint motion that goes beyond the normal range. This may occur in a forward direction (anterior), a backward direction (posterior), or in multiple directions. This section focuses on instability related to increased forward movement of the shoulder joint.

Types Of Shoulder Instability

Shoulder instability can develop from different causes. The most common types include the following:

• Dislocation Or Subluxation: A complete or partial shift of the shoulder joint out of place, often stretching or damaging ligaments and surrounding soft tissues.
• Labrum Tear: Injury to the cartilage rim that helps stabilize the shoulder, usually caused by trauma or repeated overhead movements.
• Genetic Condition: A genetic condition where joints move beyond their normal range, increasing the risk of instability without significant trauma.

Identifying Key Signs And Symptoms

Shoulder instability may lead to various symptoms, depending on the underlying cause and severity. Common signs include:

• Numbness Or Tingling Down The Arm: Abnormal sensations in the arm or hand may result from nerve irritation caused by excessive shoulder movement.
• Looseness Of The Shoulder: A sensation that the shoulder may slip, shift, or feel unstable during movement or while at rest.
• Bruising And Swelling: Damage to soft tissues around the shoulder joint may cause visible swelling or discoloration following instability or trauma.
• Tight Pecs And Shoulder Pain: Tight chest muscles or pecs can contribute to shoulder pain by restricting movement and altering posture. This may lead to discomfort, reduced range of motion, and increased strain on the neck and upper back. Read More About Tight Pecs and Shoulder Pain.
• Sternoclavicular Joint Pain: Pain in the sternoclavicular joint, which connects the collarbone to the sternum, may result from arthritis, inflammation, or injury. Accompanying symptoms can include swelling, tenderness, and discomfort with arm or shoulder movements. Read More About Sternoclavicular Joint Pain.

Common Causes Of Instability In The Shoulders

Shoulder instability may result from a variety of factors. Most causes affect the soft tissues responsible for supporting and aligning the joint.

Traumatic Dislocation

A traumatic dislocation occurs when a strong force pushes the head of the upper arm bone entirely out of the shoulder socket. This may happen during contact sports, falls, or when the arm is pulled or rotated with force.

Such injuries may stretch or tear the supporting ligaments, damage the labrum, or irritate surrounding nerves. After a dislocation, the shoulder may remain prone to future instability, particularly if the affected soft tissues do not fully recover.

Repetitive Overhead Use

Frequent overhead movements, common in sports like swimming or tennis, or in certain daily or occupational activities, can place repeated stress on the shoulder joint. Over time, this motion may gradually stretch ligaments and fatigue the muscles that help stabilize the joint.

Instability may develop slowly, without a specific injury. Individuals may notice a sense of looseness, reduced control during motion, or discomfort with activity.

Rotator Cuff Injuries

The rotator cuff consists of muscles and tendons that are key in shoulder movement and stability. Injury to these tissues due to trauma or overuse may weaken the support system around the joint.
When the rotator cuff is damaged, the shoulder may begin to shift more than usual, contributing to instability. Symptoms may include weakness, reduced range of motion, and discomfort during lifting or reaching. In some cases, rotator cuff injuries occur alongside ligament damage, which may further increase joint instability.

Weak Or Loose Ligaments 

Ligaments connect bones and help maintain proper alignment of the shoulder joint. When these tissues become stretched, weakened, or are naturally more flexible, they may lose their ability to stabilize the joint effectively.

This may occur due to prior injury, repetitive use, or a genetic tendency toward joint laxity. As a result, the shoulder may move excessively in one or more directions, contributing to instability. Individuals with loose ligaments may experience sensations of slipping, clicking, or reduced control during movement.

Age-related Degeneration Of Shoulder Tissues

Over time, the soft tissues that support the shoulder, such as ligaments, tendons, and cartilage, may gradually weaken or wear down. This natural aging process can reduce joint stability, even without a specific injury.

Age-related changes may include thinning of the labrum or decreased ligament elasticity, which can allow for excessive joint motion. Instability from degeneration often develops slowly and may present as discomfort, weakness, or a sense that the shoulder feels less secure during movement.

Bone Abnormalities

The shape and alignment of the shoulder bones are essential for maintaining joint stability. Structural differences, such as a shallow socket (glenoid dysplasia) or irregular bone contours, can affect how well the joint fits together.

These abnormalities may be present at birth or develop following an injury. When the bones do not align as expected, the shoulder may be more prone to shifting during movement. This can place added stress on surrounding soft tissues and contribute to ongoing instability.

How Is Shoulder Instability Diagnosed?

Diagnosing shoulder instability typically involves a combination of physical examination and imaging. A thorough evaluation helps identify the extent of instability, contributing factors, and any related soft tissue or structural damage. Common diagnostic methods include:

Physical Exams

A physical exam allows the physician to assess shoulder stability through guided movement and manual testing. These evaluations may check for joint looseness, abnormal motion, discomfort with movement, or signs of previous dislocation.

Imaging Techniques

Imaging plays a vital role in evaluating shoulder instability. It helps identify structural changes and allows physicians to assess joint alignment and motion with greater precision.

Stress Ultrasound

Stress ultrasound captures real-time joint movement and reveals patterns of instability that static imaging, such as MRI, may miss.

During the evaluation, the physician gently moves the shoulder while using an ultrasound probe to monitor motion at the joint. A stable shoulder shows minimal movement, while an unstable one may shift more than expected. This method allows the physician to quantify instability, track changes over time, and guide treatment planning.

Conventional Treatment Options

Physicians often begin treating shoulder instability with conservative methods. These approaches aim to reduce strain on the joint, support stability, and improve function over time:

• Activity Modification: Adjusting or avoiding activities that place stress on the shoulder can help minimize irritation and reduce the risk of further instability.
• Physical Therapy: Targeted exercises strengthen the rotator cuff and surrounding stabilizing muscles, helping the joint stay aligned and reducing excessive movement during activity.

• Shoulder Dislocation Surgery: Surgery for a shoulder dislocation may involve repairing torn ligaments or stabilizing the joint to help prevent recurrent dislocations. It is often considered for individuals with chronic instability. Read More About Shoulder Dislocation Surgery.

Explore A Non-Surgical Approach to Shoulder Instability

Many cases of shoulder instability can be managed without surgery. Physicians in the licensed Regenexx network use image-guided procedures to support joint stability by targeting damaged tissues. Stress ultrasound imaging captures real-time joint movement, allowing physicians to identify instability and guide treatment. Depending on severity, care may involve PRP injections or, in advanced cases, stem cell-containing bone marrow concentrate through the Regenexx-SD injectate.

These orthobiologic procedures may help reduce discomfort, may promote natural tissue repair, and may help enhance joint control over time. Progress can be monitored objectively through follow-up stress ultrasound imaging, helping guide ongoing care. 

For individuals seeking to avoid surgery, this image-guided, less invasive approach may offer a way to help address the underlying condition of shoulder instability while closely tracking recovery.

Medically Reviewed By:

Dr. Chaz Fausel, MD

Dr. Chaz Fausel is a Denver-based interventional orthopedics specialist and Regenexx educator, trained at Emory and the Centeno-Schultz Clinic.