Shoulder Instability: Causes, Types, and Treatment Options

Written By Dr. Mica Flores

The shoulder is the most mobile—and least stable—joint in the human body, allowing movement in multiple planes. Shoulder instability occurs when the head of the humerus is unable to remain properly centered within the glenoid fossa during movement.

Instability exists on a spectrum. In some cases, the humeral head partially translates beyond normal limits while still maintaining contact with the glenoid—this is known as a subluxation. In more severe cases, the humeral head moves completely beyond the rim of the glenoid, resulting in a dislocation. When the surrounding anatomical structures can no longer control this motion, symptoms such as pain, weakness, and loss of function often develop.

The glenohumeral joint relies on a complex balance of static and dynamic stabilizers. When one or more of these structures are compromised—through trauma, repetitive stress, or connective tissue laxity—shoulder instability can develop.

Common injuries associated with shoulder instability include:

  • Subluxation

  • Dislocation (with or without reduction)

  • Rotator cuff tears

  • Hill-Sachs lesions

  • Bankart lesions

Anatomy of Shoulder Stability

Static Stabilizers

These structures provide passive stability to the shoulder:

  • Glenoid labrum

  • Joint capsule

  • Glenohumeral ligaments

  • Negative intra-articular pressure

Dynamic Stabilizers

These muscles actively control shoulder motion:

  • Rotator cuff: supraspinatus, infraspinatus, teres minor, subscapularis

  • Periscapular muscles: serratus anterior, rhomboids, trapezius, latissimus dorsi, pectoralis minor

  • Deltoid

Proper coordination between these stabilizers is essential for maintaining shoulder health.

Types of Shoulder Instability

Anterior Shoulder Instability

Anterior instability is the most common type, accounting for approximately 95% of instability events. It occurs when the humeral head translates forward (anteriorly), often during positions of abduction and external rotation.

This can result from:

  • Traumatic events (falls, collisions)

  • Repetitive overhead movements

Anterior instability is more common in younger individuals due to ligamentous laxity, while adults over age 40 often experience instability related to rotator cuff tears.

Sports with higher risk include:

  • Baseball

  • Volleyball

  • Swimming

Posterior Shoulder Instability

Posterior instability is less common, accounting for approximately 2–5% of cases, but is still seen in active populations. It typically occurs when the shoulder is placed in flexion, adduction, and internal rotation.

It may result from:

  • Repetitive microtrauma

  • High-force macrotrauma

Posterior instability is more frequently seen in males ages 20–30, particularly in:

  • Weightlifting

  • Contact sports such as football

Multidirectional Shoulder Instability

Multidirectional instability involves instability in two or more planes (anterior, posterior, and/or inferior). It is most common in individuals aged 20–30 years and is often associated with repetitive microtrauma from overhead activities.

It may also be linked to generalized joint laxity seen in conditions such as:

  • Ehlers-Danlos syndrome

  • Marfan syndrome

  • Osteogenesis imperfecta

  • Hypermobility spectrum disorders

Common Clinical Signs and Symptoms

  • Shoulder pain (anterior, posterior, or deep ache)

  • Weakness or fatigue

  • Popping, clicking, or catching sensations

  • Neurological symptoms (tingling or burning)

  • Crepitus

  • Excessive range of motion

  • Poor dynamic control

Treatment Options for Shoulder Instability

Physical therapy is typically the first line of treatment for shoulder instability and has been shown to be highly effective, particularly for:

  • Adults over age 40

  • Individuals not involved in high-demand overhead sports

Conservative management focuses on:

  • Scapular posture and control

  • Strengthening dynamic stabilizers

  • Proprioception and neuromuscular control

  • Functional and sport-specific training

Research supports that a comprehensive, individualized rehab program can significantly reduce symptoms and often help patients avoid surgery.

For younger athletes involved in high-demand overhead or contact sports, surgical intervention may be recommended after an acute dislocation due to a higher risk of recurrent instability. Following immobilization, physical therapy is essential to restore function and safely return to sport.

Examples of Beneficial Exercises

  • Plank and single-arm plank

  • Side plank variations

  • Plank drags

  • High plank on unstable surfaces

  • Isometric internal and external rotation walkouts

  • Prone T’s, W’s, and Y’s

  • Carries (farmer’s, waiter’s, overhead)

  • PNF diagonal patterns

  • Jobe’s rotator cuff exercises

Exercise selection should always be tailored to the individual’s symptoms, goals, and activity demands.

Dr. Mica Flores

Mica has a passion for helping patients of all ages whether it is returning to sport after injury or reducing pain.
She believes in tailoring each session specific to the patient’s needs. With good communication, exercise, and hands on care, Mica works to guide each patient to achieving their goals. Mica is a San Francisco native and in her free time she enjoys traveling, cooking, dancing, soccer, exploring in the outdoors and spending time with friends and family.

https://kauno.health/micaflores
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