Multi-Directional Instability of the Shoulder

The shoulder joint is a complex joint that allows more motion than any other joint in the body. This joint mobility is usually stable and well controlled.

But some people have shoulder joints that are too mobile. This may make the shoulder more likely to move out of joint. When the shoulder does not sit as tightly as it should within the joint, it's called shoulder instability.

This article will discuss the multi-directional instability of the shoulder, also known as "swimmer's shoulder," a condition where the shoulder joint is too loose. Keep reading to learn what causes multi-directional instability, its symptoms, and how your doctor diagnoses and treats it.

Overview of Shoulder Instability

The shoulder is a ball-and-socket joint. Sometimes the ball comes partially out of the socket—a condition described as a shoulder subluxation. And if the ball comes completely out of the socket, this is a shoulder dislocation.

There are two general types of shoulder instability:

• Traumatic instability: Traumatic shoulder instability occurs because of a fall or sports injury. The shoulder is forcefully pulled out of its socket, and often must be placed back into position with special maneuvers. Sometimes the procedure requires anesthesia. A traumatic dislocation can damage the ligaments that hold the ball in the socket, making the shoulder more likely to separate again in the future.
• Multi-directional instability: Multi-directional instability (MDI), also called atraumatic instability, occurs when the shoulder joint is loose within the socket. There may not be a traumatic event that causes the instability. Instead, the shoulder constantly shifts around. It causes pain and limited function in the joint. Often, people who have symptoms of multi-directional instability complain of clunking or shifting of the shoulder when they reach overhead in sports like gymnastics, swimming, or athletics that require throwing.

Causes of MDI

There are three factors that contribute to the stability of any joint in the body. These include:

• Bone anatomy: The bones of the shoulder contribute very little to the stability of this joint. The shoulder socket is very shallow. Without other structures to hold it in place, the ball would not stay in position. Compare this to the hip joint, which has a very deep socket, a shape that helps the ball remain stable in the socket.
• Static stabilizers: These are the ligaments that surround the joint. Ligaments are tough bands of tissue that connect two bones together. Ligaments are flexible (they can bend), but not elastic (they do not stretch). Shoulder instability is associated with torn ligaments of the shoulder joint. Multi-directional instability is often caused by loose ligaments. There are genetic conditions that can sometimes affect the ligaments and cause severe multi-directional instability.
• Dynamic stabilizers: The dynamic stabilizers are the muscles and tendons around the shoulder. These muscles include the rotator cuff, a group of muscles that surrounds the ball of the shoulder. Dynamic stabilizers are flexible and elastic. Many people with multi-directional instability can strengthen the shoulder muscles to make up for loose ligaments.

Symptoms

While most people who have symptoms related to multi-directional instability participate in sports involving overhead movements including gymnastics and softball, it is most associated with aquatic sports, which is why it is called "swimmer's shoulder." Young women are most commonly affected by multi-directional instability. Symptoms of multi-directional shoulder instability include:

• Pain and instability with overhead activities
• The feeling that your shoulder is slipping out of its position
• Popping or grinding in the shoulder joint
• Weakness in your shoulder

Diagnosis

When doctors diagnose multi-directional instability in the shoulder, they consider your medical history. They also do a thorough medical exam. Your doctor will move your arm around in various positions to determine how mobile your shoulder is.

Your doctor may order tests of your shoulder. There are several tests to properly diagnosis multidirectional instability and some of those include:

• X-rays: X-rays are used to look at the bones inside your shoulder and arm. This will help your doctor see any injuries or possible bone structure problems you've had since birth.
• Magnetic resonance imaging (MRI): MRIs are used to look at the organs and tissues inside your body. Your doctor can use an MRI to find other sources of your shoulder pain, such as arthritis, tendinitis (inflammation of the tendon), or a fracture.
• Computed tomography (CT): CT scans combine x-rays and computer technology to give the most precise pictures of the shoulder.
• Arthroscopy: Arthroscopy is a procedure where the doctor uses a video camera on a narrow tube inserted through small incisions to look for problems inside the joint. If necessary, the doctor can also use thin instruments to correct the joint issue.

Treatment

The treatment of MDI is different from treatment for traumatic instability of the shoulder. Usually, people can recover from multi-directional instability with non-surgical treatments. This includes high-level, competitive athletes.

Treatment should focus on strengthening the muscles and tendons of the shoulder joint. This is done with physical therapy.

Multi-directional instability can also happen when the shoulder blade movements are not well-coordinated with the shoulder movements. Shoulder joint function can improve when you restore normal shoulder blade motion with strengthening exercises.

Many studies have shown that most people can recover from multi-directional instability with a focused shoulder rehab program. Many patients who undergo such a program will report good results. However, some people don't improve and may need to have shoulder surgery.

Surgery

Surgical procedures for MDI are considered for patients who continue to have symptoms of shoulder instability despite non-surgical treatments. Usually, the surgery involves tightening the ligaments that surround the shoulder. This can be done with arthroscopic surgery or standard surgical incisions.

The best surgery for multi-directional instability is called a capsular shift or capsular plication. These are procedures that tighten the shoulder capsule, a group of ligaments that surround the ball-and-socket joint. The doctor may also recommend a rotator interval closure, a procedure that closes the gap between two of the rotator cuff muscles.

Thermal shrinkage, using heat probes to burn soft tissue in the shoulder to tighten the joint capsule, is a procedure that is no longer used but was popular not long ago. Thermal shrinkage procedures had very poor results and often required additional surgery. If you have had thermal shrinkage treatment, you might need surgery if your symptoms return.

People usually receive several months of rehab after surgery for multi-directional instability. Initially, after surgery, the shoulder is kept from moving to allow the tightened tissues to heal. For example, the doctor may have you wear a sling.

Then motion is gradually started to regain mobility, followed by strengthening exercises. Most athletes are allowed to resume full activity within six months.

Summary

Multi-directional instability (MDI) happens when the shoulder joint is loose in the socket. You may experience pain or instability when reaching overhead. You may even feel a popping in your shoulder joint. Sometimes your shoulder may feel like it's slipping out of its position. Fortunately, your doctor can diagnose MDI and create a treatment plan to help you recover from this medical condition.