Shoulder Instability

Anatomical graphic of the shoulder and is demonstrating shoulder instability


Shoulder instability means that the shoulder joint is too loose and is able to slide around too much in the socket. In some cases, the unstable shoulder actually slips out of the socket. If the shoulder slips completely out of the socket, it has become dislocated. If not treated, instability can lead to arthritis of the shoulder joint.

This guide will help you understand

  • What parts of the shoulder are involved
  • What causes shoulder instability
  • What treatments are available


The shoulder is made up of three bones: the scapula (shoulder blade), the humerus (upper arm bone,) and the clavicle (collarbone).

The rotator cuff connects the humerus to the scapula. The rotator cuff is actually made up of the tendons of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis.

Tendons attach muscles to bones. Muscles move bones by pulling on tendons. The muscles of the rotator cuff also keep the humerus tightly in the socket. A part of the scapula, called the glenoid, makes up the socket of the shoulder.

The glenoid is very shallow and flat. A rim of soft tissue called the labrum, surrounds the edge of the glenoid, making the socket more like a cup. The labrum turns the flat surface of the glenoid into a deeper socket that molds to fit the head of the humerus.

Surrounding the shoulder joint is a watertight sac called the joint capsule. The joint capsule holds fluids that lubricate the joint. The walls of the joint capsule are made up of ligaments. Ligaments are soft connective tissues that attach bones to bones.

The joint capsule has a considerable amount of slack, loose tissue so that the shoulder is unrestricted as it moves through its large range of motion. If the shoulder moves too far, the ligaments become tight and stop any further motion, sort of like a dog coming to the end of its leash.

Anatomical graphic of the shoulder showing shoulder instability but is labeled on the bone of the clavical, glenoid, head of humerus, join capsule, and scapula

Dislocations happen when a force overcomes the strength of the rotator cuff muscles and the ligaments of the shoulder. Nearly all dislocations are anterior dislocations, meaning that the humerus slips out of the front of the glenoid. Only three percent of dislocations are posterior dislocations, or out the back.

Sometimes the shoulder does not come completely out of the socket. It slips only partially out and then returns to its normal position. This is called subluxation.

Related Document: A Patient’s Guide to Shoulder Anatomy


Shoulder instability often follows an injury that caused the shoulder to dislocate. This initial injury is usually fairly significant, and the shoulder must be reduced. To reduce a shoulder means it must be manually put back into the socket.

The shoulder may seem to return to normal, but the joint often remains unstable. The ligaments that hold the shoulder in the socket, along with the labrum (the cartilage rim around the glenoid), are typically stretched or torn. This makes them too loose to keep the shoulder in the socket when it moves in certain positions. An unstable shoulder can result in repeated episodes of dislocation, even during normal activities. Instability can also follow less severe shoulder injuries.

In some cases, shoulder instability can happen without a previous dislocation. People who do repeated shoulder motions may gradually stretch out the joint capsule. This is especially common in athletes such as baseball pitchers, volleyball players, and swimmers.

If the joint capsule gets stretched out and the shoulder muscles become weak, the ball of the humerus begins to slip around too much within the shoulder. Eventually, this can cause irritation and pain in the shoulder.

A genetic problem with the connective tissues of the body can lead to ligaments that are too elastic. When ligaments stretch too easily, they may not be able to hold the joints in place. All the joints of the body may be too loose. Some joints, such as the shoulder, may be easily dislocated. People with this condition are sometimes referred to as double-jointed.


What problems does an unstable shoulder cause?

Chronic instability causes several symptoms. Frequent subluxation is one. In subluxation, the shoulder may slip (sublux) in certain positions, and the shoulder may actually feel loose. This commonly happens when the hand is raised above the head, for example, while throwing. Subluxation of the shoulder usually causes a quick feeling of pain, like something is slipping or pinching in the shoulder. Over time, you may stop using the shoulder in ways that cause subluxation.

The shoulder may become so loose that it starts to dislocate frequently. This can be a real problem, especially if you can’t get it back in the socket and must go to the emergency room every time. A shoulder dislocation is usually very obvious. The injury is very painful, and the shoulder looks abnormal. Any attempted shoulder movements cause extreme pain. A dislocated shoulder can damage the nerves around the shoulder joint.

Anatomical graphic of nerves that have been stretched weakening the shoulder causing shoulder instability

If the nerves have been stretched, a numb spot may develop on the outside of the arm, just below the top point of the shoulder. Several of the shoulder muscles may become slightly weak until the nerve recovers., but the weakness is usually temporary.


Dr. Kiritsis will diagnose shoulder instability primarily through your medical history and physical exam. The medical history will include many questions about past shoulder injuries, your pain, and the ways your symptoms are affecting your activities.

In the physical exam, Dr. Kiritsis will feel and move your shoulder, checking it for strength and mobility. He will stress the shoulder to test the ligaments. When the shoulder is stretched in certain directions, you may get the feeling that the shoulder is going to dislocate. This is a very important sign of instability. It is called an apprehension sign

Dr. Kiritsis will order an X-ray. X-rays can help confirm that your shoulder was dislocated or injured in the past.

If Dr. Kiritsis is unsure about the diagnosis, he may order an MRI. An MRI is typically done after the dye is injected into the shoulder. An MRI scan is a special imaging test that uses magnetic waves to show the tissues of the shoulder in slices. The MRI scan shows soft tissues such as tendons and ligaments as well as bones.

Nonsurgical Treatment

Dr. Kiritsis’first goal will be to help you control your pain and inflammation. Initial treatment to control pain is usually rest and anti-inflammatory medication, such as ibuprofen or Aleve.

Dr. Kiritsis will probably have a physical or occupational therapist direct your rehabilitation program. At first, patients are shown ways to avoid positions and activities that put the shoulder at further risk of injury or dislocation. Overhand athletes may be issued a special shoulder strap or sleeve to stop the shoulder from moving in ways that could cause a dislocation.

Your therapist may use heat or ice treatments to ease pain and inflammation. Hands-on treatments and various types of exercises are used to improve the range of motion in your shoulder and nearby joints and muscles.

Later, you will do strengthening exercises to improve the strength and control of the rotator cuff and shoulder blade muscles. Your therapist will help you retrain these muscles to keep the ball of the humerus in the socket. This will improve the stability of the shoulder and help your shoulder joint move smoothly.

You may need therapy treatments for six to eight weeks. Most patients are able to get back to their activities with full use of their arms within this amount of time.


Many different factors play into the decision of proceeding with surgery.  Dr. Kiritsis will review all of your options with you so you can make an informed decision. The main goal of surgery is to reduce and/or stabilize the shoulder. Restoring normal motion and function and preventing recurrent dislocations are important outcomes of surgical intervention.

Even when surgery is needed, Dr. Kiritsis may have you see a physical therapist for several visits before the surgery. This is done to reduce swelling, strengthen the muscles, and stabilize the shoulder as much as possible before surgery. This practice also reduces the chances of scarring inside the joint and can speed recovery after surgery.

There are many different ways to repair a chronically unstable shoulder following a first dislocation or after many recurrent shoulder dislocations. The direction of instability (anterior, posterior, inferior, or some combination) is taken into consideration when choosing the best reconstructive technique. The site, type, and extent of damage are major determining factors in how the surgeon approaches the repair.

One of the most common procedures is the Bankart operation. During the Bankart reconstruction procedure, the labrum and capsule are reattached to the anterior margin of the glenoid cavity.

Graphic showing how surgery is performed on a women of a dislocated shoulder

Shoulder reconstruction surgery may be done with an open incision method or with the aid of an arthroscope. . The arthroscope is used to view the inside of the shoulder joint as the surgeon performs the work.  Please view the video at the beginning of this section.  

Anatomical graphic of a bankart repair of a shoulder dislocation

Older adults who have a fracture and shoulder dislocation may need a shoulder replacement instead of shoulder reconstructive surgery to reduce the dislocation and repair the fracture.

Some patients fracture the rim of the glenoid, which causes the joint to be very unstable and leads to recurrent episodes of instability.  Dr. Kiritsis has experience in the arthroscopic treatment of glenoid bone defects. The video below is a surgical demonstration of my bone grafting technique.

Arthroscopic Glenoid Bone Graft

Capsular Shift

Another surgery to tighten a loose shoulder joint is a procedure called a capsular shift. The lining of any joint is called the joint capsule. The joint capsule forms a pocket, or bag that is made up of the ligaments and connective tissue around the joint. The shoulder joint has a fairly large joint capsule that is necessary to allow the joint to move in such a wide range.

Anatomical graphic of the Capsular Shift

Sometimes the problem causing the shoulder instability is because the joint capsule is simply too large. This is sometimes referred to as a redundant, or patulous joint capsule. This may cause shoulder instability in multiple directions. This is sometimes referred to as multi-directional instability. In order to fix this type of instability, the joint capsule needs to be made smaller and tightened.

Anatomical graphic of the capsular shift to make the joint smaller and fix the shoulder instability

This procedure is performed using the arthroscope. Dr. Kiritsis pulls the flap of tissue over the front of the capsule and connects it together. This is similar to when a tailor tucks loose fabric by overlapping and sewing the two parts together. Once the appropriate degree of tightness is achieved, Dr. Kiritsis uses a combination of sutures and suture anchors to hold the joint capsule in this position until healing occurs.

Nonsurgical Rehabilitation

Patients may receive physical therapy after having a dislocation. Therapists treat swelling and pain and help minimize tension on inflamed structures with the use of ice, supportive taping, electrical stimulation, and rest periods. Symptoms are addressed in the acute phase but restoring normal function rather than eliminating symptoms is the focus for chronic shoulder instability.

Exercises are used to help you regain normal movement of joints and muscles. Range-of-motion exercises should be started right away with the goal of helping you swiftly regain full movement in your shoulder. This includes the use of gentle stretching and motion through the full range available.

As your symptoms ease and strength improves, you will be guided in specialized exercises to improve posture, shoulder stability, and normal motor control. The desired final outcome is a return to full function. For athletes, this means full participation in sports activities.

In the later phase of rehab, the therapist will use a combination of kinetic chain exercises to decrease shear forces on the joint while enhancing strength. Plyometrics, a specific type of exercise to produce fast, powerful movements needed for sports performance will also be included.

You can return to your sporting activities when your muscles are back to their full strength and control, you are pain-free, and you aren’t having problems with the shoulder popping out of the joint.

After Surgery

After any surgery to stabilize the shoulder your shoulder will be immobilized. You will wear a sling for four to six weeks. A large abduction wedge under the armpit may be used to hold the arm in just the right position. The soft tissues must be given enough time to heal and form scar tissue to support and stabilize the shoulder joint.

Dr. Kiritsis will have you take part in formal physical therapy after shoulder reconstruction. You will probably be involved in a progressive functional rehabilitation program. The phases of rehabilitation include acute, early recovery, late recovery, and functional phase.

You should expect functional rehab to last four to six months after surgery. This will ensure the best result from your reconstruction. During the acute phase (one to three weeks), you may expect to see the physical therapist two to three times a week. The goal is to control pain and inflammation. The therapist will address any postural abnormalities and begin muscle re-education.

When you have minimal pain and adequate soft tissue healing, you’ll be advanced to the early recovery phase. This phase usually lasts from three to six weeks after the surgery. During this time, the therapist will work with you to increase motion, strength, and control.

When you have full, pain-free motion and improved strength, then you’ll enter the late recovery phase. This phase extends from six to 12 weeks postoperatively. Improving strength, power, endurance, and dynamic kinetics (movement) is the main thrust of the late recovery phase.

The functional phase begins about three months after surgery. This phase is directed at the sports athlete. The therapist will put you through a series of drills designed to improve coordination, speed, and agility. In order to participate in this level of rehab, you must have a normal range of motion, flexibility needed for your sport or activity, and 90 percent of normal strength. You must also be free of symptoms during activities or sport-specific drills.

A portrait of Doctor Paul Kiritsis, MD smiling.

Paul Kiritsis, MD

Dr. Kiritsis, a Richmond native, is one of a select number of Orthopedic Surgeons in the Richmond area to hold a second subspecialty board certification in Sports Medicine.

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