Shoulder Instability Causes, Symptoms & Treatment Options
Shoulder instability occurs when the ligaments and muscles fail to keep the humeral head securely in the glenoid fossa, causing partial (subluxation) or complete dislocation. It can result from trauma, repetitive stress, or naturally loose joints. Treatment includes physical therapy, bracing, or surgery for recurrent or severe cases.
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Find Relief TodayOverview
The shoulder is a complex joint formed at the junction of three bones: the head of the humerus, which is the long bone of the upper arm; the scapula, commonly known as the shoulder blade; and the clavicle, or collarbone.
The rounded head of the humerus fits snugly into a shallow cavity on the scapula called the glenoid fossa, creating the glenohumeral joint. This ball-and-socket joint allows for a wide range of motion, including rotation, lifting, and swinging of the arm, making the shoulder one of the most mobile and versatile joints in the body.
What causes Shoulder Instability?
The shoulder is a highly flexible joint with a wide range of motion, allowing movements like throwing a ball. However, this mobility makes it prone to instability, where the ligaments and muscles cannot keep the humeral head securely in the glenoid fossa. Instability can be partial, called a subluxation, or complete, called a dislocation.
- Subluxation: A partial shoulder dislocation where the humeral head slightly slips out of the glenoid fossa.
- Dislocation: The humeral head completely leaves the glenoid fossa, which can be traumatic (from impact) or atraumatic (from capsule stretching); traumatic dislocations often tear the labrum.
How the Injury Occurs: Instability happens when sudden force, repetitive stress, or overextension overpowers the shoulder’s stabilizing ligaments and muscles, allowing the humeral head to slip partially or completely out of the socket.
Common Everyday Causes: Falls, heavy lifting, repeated overhead movements, or even sleeping in awkward positions can gradually loosen the shoulder and increase the risk of subluxation or dislocation.
Shoulder instability can occur in three different ways:
- Anterior instability: The humerus is pushed out through the front of the shoulder, often from falls or overextension.
- Posterior instability: The humerus is forced out through the back of the shoulder, typically from direct trauma or repeated pressing movements.
- Multidirectional instability: The humerus moves out in multiple directions due to generalized laxity or overuse.
Shoulder instability is classified into either:
- Traumatic instability: Results from injury or impact, causing ligament or labrum damage.
- Atraumatic instability: Occurs from repetitive overuse or naturally loose joints without a specific injury.
Shoulder instability is common in these sports:
- Football: Tackles and collisions put extreme stress on the shoulder joint.
- Rugby: Frequent impacts and falls increase the risk of dislocation or subluxation.
- Swimming: Repetitive overhead motions can stretch ligaments and destabilize the shoulder.
- Volleyball: Jumping and hitting motions repeatedly stress the shoulder joint.
- Basketball: Falls, collisions, and overhead movements can contribute to instability.
Symptoms
Shoulder instability may cause pain, but sometimes the shoulder simply feels loose or unstable. Shoulder instability symptoms include:
- Your shoulder feels loose or out of place: A sensation of the joint slipping, shifting, or moving more than usual.
- Repeated shoulder dislocations or subluxations: The shoulder may partially or fully “pop out,” especially during sports or sudden movements.
- Pain with certain arm positions: Pain often occurs when the arm is raised overhead, rotated, or moved away from the body.
- A feeling that the shoulder might give out: The shoulder may feel weak or unreliable during lifting, throwing, or pushing activities.
When to see a doctor
If you experience pain, repeated looseness, or episodes where the shoulder feels like it might slip out, you should consult a doctor.
During your appointment, your doctor may:
- Examine your shoulder for signs of instability: Checking movement, strength, and pain points.
- Look for signs of laxity or looseness in other joints: To assess generalized joint flexibility.
- Obtain X-rays: To evaluate bone alignment and check for dislocations or fractures.
- Obtain an MRI or CT scan: To assess soft tissue structures, including ligaments, labrum, and cartilage.
Non-operative treatment
For first-time shoulder instability or a partial dislocation, doctors often recommend conservative, non-surgical treatment. This typically involves a home exercise program or a supervised program with a licensed physical therapist to strengthen the muscles around the unstable shoulder joint, improve stability, and prevent future dislocations.
Try these exercises to help address your condition:
Below is a PDF of the Exercise Program
Surgical Treatment
If you have injured the muscles or ligaments of the shoulder, you may need surgery to repair damaged tissue and/or to tighten any ligaments that are stretched out. If you have more than one dislocation, oftentimes, surgery is suggested to stabilize the shoulder.
The type of procedure performed will depend on many factors, including:
- Whether the shoulder is dislocating out of the back or the front of the joint
- If there is any damage to the bone
- The number of times the shoulder has been dislocated
Generally, in simple cases, surgery can be done arthroscopically. Arthroscopic surgery is a minimally invasive surgical technique that uses several tiny incisions (roughly one centimeter long) through which special instruments and a camera, attached to a thin, flexible tube, are inserted. During arthroscopic surgery, the physician repairs the torn labrum by putting stitches in the torn tissue. In complicated cases, a more classic open procedure is needed to restore the stability of the shoulder joint.
Recovery
Your recovery time will vary depending on the extent of your injuries and whether you need surgery. In situations where surgery is not needed, your shoulder may be immobilized for 10 days to up to three weeks, followed by a course of physical therapy.
Depending on the sport, you may be able to return to play in six weeks. However, in some higher-demand sports, oftentimes play is restricted for three months. Your doctor may recommend that you wear a brace when you return to play for added protection.
If you need surgery, you will be required to keep your arm in a sling for two to three weeks to allow the shoulder to heal. Full recovery can take up to six months. You can return to play when you have recovered a full range of motion and strength and do not have pain.
Dr. Jay Kimmel is a board-certified orthopedic surgeon specializing in sports medicine, arthroscopic surgery, and shoulder and knee disorders. He completed his orthopedic training at New York-Presbyterian/Columbia University Medical Center and a Sports Medicine Fellowship at Temple University.
Dr. Kimmel previously served as the Director of the Connecticut Sports Medicine Institute at Saint Francis Hospital and has held faculty appointments as Clinical Assistant Professor in the Departments of Orthopedics and Family Medicine at the University of Connecticut. He has extensive experience caring for athletes as a team physician for high school and collegiate programs and continues to teach in the athletic training departments at Westfield State University and Springfield College.
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/MonthFrequently Asked Questions
What is the most frequent direction of shoulder dislocation?
The humeral head most commonly dislocates in an anterior (forward) and inferior (downward) direction.
If my shoulder pops out, is it always going to be unstable?
Not always, while some people go on to have multiple episodes of instability, many individuals can regain shoulder stability and normal function with appropriate treatment, including physical therapy and strengthening exercises. In some cases where the shoulder remains unstable, surgery is needed to stabilize the shoulder.
What causes atraumatic shoulder instability?
Atraumatic shoulder instability can be linked to several factors, such as a shallow or underdeveloped socket, weak shoulder muscles, and overly flexible ligaments. A consistent regimen of stabilizing exercises is typically the first line of treatment.
How is shoulder instability diagnosed?
Shoulder instability is typically diagnosed through a physical examination, patient history, and imaging tests like X-rays or MRIs, which can help identify any labral tears, bone damage, or muscle weakness contributing to instability.