Multidirectional instability of the shoulder is defined as generalized looseness (laxity) of the shoulder joint due to increased mobility and joint weakness. Many factors, including congenital looseness, muscular imbalances, shoulder blade position, shoulder structure variations, and certain repetitive activities, can contribute to the development of MDI. When the shoulder becomes loose, the joint may "slip" in and out of its socket in more than 1 direction—forward (anterior), backward (posterior), or downward (inferior). This laxity may be exaggerated in people who participate in activities that require repeated overhead movement of the arm, such as baseball pitchers or swimmers. Overuse of the shoulder is often associated with and contributes to MDI. MDI is less common in people aged 40 years and older due to the natural stiffening of the tissues around the shoulder with age.

Symptoms of MDI of the shoulder may vary in terms of their location and intensity. Although sometimes the shoulder can be dislocated, often people report their shoulder will "slip" out of its socket and go right back into it. They also may report instances where they feel like their shoulder is about to slip in and out of its socket, but they modify their activity to prevent it from happening. Some individuals will even avoid certain movements due to their fear that the shoulder will “pop out.”

Pain caused by MDI may be felt in a number of areas around the shoulder—in the front of the shoulder when pitching a baseball, or throughout the entire shoulder after a repetitive activity like swimming. Symptoms of MDI vary widely; your health care professional will likely take a detailed health history and perform a thorough physical examination to make an accurate diagnosis.

Signs and symptoms of MDI of the shoulder vary from person to person, but may include:

• Pain and/or instability with pushing, pulling, or carrying heavy objects.
• Pain and/or instability when performing an overhead activity.
• Pain and/or instability during or after exercise.
• A feeling that the shoulder is "shifting" (including in bed at night).
• The sensation of the shoulder slipping out of its socket and back into it.
• Fear of putting the shoulder in certain positions.
• Numbness and tingling sensations in the affected arm.
• Clicking and popping sensations with movement.
• Weakness when performing athletic movements, especially overhead and away from the body.
• Loss of performance ability in sport activities.
• Fatigue with repetitive activity.

Your physical therapist will take a detailed health history, and assess the mobility of the shoulder joint in a variety of positions as well as the strength of the rotator cuff and scapular muscles. Your therapist also may assess your core strength, the presence of any nerve involvement, your joint-body awareness, and your overall muscle control. Your physical therapist may gently pull downward on the shoulder to look for increased movement in the joint, or push forward or backward on the arm bone within the shoulder joint to assess increased areas of mobility. Your therapist will use a cluster of shoulder instability tests to help diagnose MDI.

For a more detailed diagnosis, a physician may order x-rays to rule out bone fractures, and can order an MRI to diagnose injury within the shoulder complex, such as a muscle, capsule, or labral tear.

Your physical therapist will evaluate your shoulder injury and find areas of weakness and muscular imbalance. The first step to treating the injury is managing pain and inflammation. Your physical therapist may advise you to stop or modify any activities that aggravate the injury and show you techniques to lessen pain, omitting the need for strong medications, such as opioids.

Your physical therapist will design an exercise program to improve your shoulder's strength and stability and address other factors that contribute to your lack of stability, such as your core strength and body awareness. Initially, you'll perform gentle exercises close to the body to limit your discomfort. After strength and stability have improved, your physical therapist will introduce more dynamic exercises specific to your activity goals. The dynamic exercises are created specifically to improve your body’s ability to handle the stress and demands of your activities, work, and/or sport. 

Physical therapists help athletes with MDI gradually return to sport once their strength and range of motion have returned to normal levels. Throwing, playing, or swimming will typically begin in an interval format, allowing a progressive return to activity.

Although MDI cannot be totally prevented, physical therapy can lessen the effects of shoulder laxity. Controlling MDI of the shoulder falls into 3 categories:

• Strengthening the scapular muscles and the muscles of the rotator cuff by improving shoulder mechanics, muscular imbalances, body awareness, and muscle control. Athletes may perform scapular and rotator cuff strengthening exercises 3 to 4 times per week.
• Monitoring the volume of activity performed. This practice is just as important as strengthening exercises. Baseball players, for example, will often use pitch counts to avoid overuse injuries; swimmers attempt to maintain weekly yardage totals.
• Maintaining proper form and technique. Good coaching on proper form and technique by a qualified coaching professional can be a valuable asset in preventing injuries in the young athlete population.

All physical therapists are prepared through education and experience to treat multidirectional instability. However, you may want to consider:

• A physical therapist who is experienced in treating people with multidirectional instability. Some physical therapists have a practice with a sports or orthopedic focus.
• A physical therapist who is a board-certified clinical specialist or who completed a residency or fellowship in sports or orthopedic physical therapy. This physical therapist has advanced knowledge, experience, and skills that may apply to your condition.

You can find physical therapists who have these and other credentials by using Find a PT, the online tool built by the American Physical Therapy Association to help you search for physical therapists with specific clinical expertise in your geographic area.

General tips when you're looking for a physical therapist (or any other health care provider):

• Get recommendations from family, friends, or other health care providers.
• When you contact a physical therapy clinic for an appointment, ask about the physical therapists' experience in helping people who have multidirectional instability.
• Be prepared to describe your symptoms in as much detail as possible, and say what makes your symptoms worse.