The acromioclavicular (AC) joint is a small but functionally important joint located at the top of the shoulder where the collarbone (clavicle) meets the highest part of the shoulder blade (acromion). An AC joint injury, often called a shoulder separation, occurs when the ligaments stabilizing this connection are stretched or torn. The most common mechanisms of injury involve a direct blow to the tip of the shoulder or a fall onto the shoulder with the arm tucked against the body.
These injuries are classified by severity using a grading system, most commonly the Rockwood classification, which ranges from a mild sprain (Type I) to a complete tear of the stabilizing ligaments (Type III and above). Regardless of the grade, pain and limited movement are common symptoms, and a visible bump or deformity may be present with more severe injuries. This guide details the exercises typically used in recovery; however, you must consult a physical therapist or physician for a personalized diagnosis and exercise plan before beginning any rehabilitation program.
Immediate Care and Safety Guidelines
The initial phase following an AC joint injury focuses on protecting the joint and managing acute symptoms, often lasting the first few days to a week. The immediate care protocol often includes relative rest, which means avoiding activities that cause pain, especially lifting the arm above the shoulder or carrying heavy objects. A physician may prescribe a sling for a short period to immobilize the joint and reduce stress, particularly for more severe Type II or Type III sprains.
Pain signals stress and is a contraindication to movement. If an exercise causes a sharp increase in pain, stop immediately or regress to a gentler version. Maintaining upright shoulder girdle posture is important, as slouching strains the healing ligaments and muscles. Icing the area multiple times a day helps minimize swelling and manage localized pain, supporting the initial healing process.
Early Phase Rehabilitation Exercises
Once the initial acute pain has subsided, the focus shifts to gentle, pain-free movement to prevent stiffness and begin restoring the shoulder’s range of motion (ROM). The goal during this early phase is passive and active-assisted ROM, meaning the injured arm is moved without actively engaging the surrounding muscles against gravity or resistance. These exercises are generally performed below shoulder height to protect the healing ligaments from excessive stress.
Pendulum exercises, also known as Codman exercises, are often the first movement introduced. This involves leaning over and letting the injured arm hang down, using the body’s momentum to swing the arm in small circles or forward and back while keeping the shoulder muscles relaxed. Finger walking up a wall assists in regaining forward flexion and abduction. By using the fingers to “walk” the hand up the wall, the movement is controlled and assisted, preventing the shoulder muscles from lifting the arm against gravity.
Gentle isometric squeezes can be performed to begin activating supporting muscles without stressing the joint. This involves tensing surrounding muscles, such as the biceps or triceps, by holding a rolled towel or ball without moving the joint. These contractions are held for about five seconds at low intensity, helping to maintain muscle tone and stimulate neuromuscular control without causing shearing forces on the AC joint. Controlled movement promotes circulation and prevents the formation of excessive scar tissue in the joint capsule.
Mid-Phase Recovery Exercises
The mid-phase begins once the patient has achieved near-full passive ROM and the pain is minimal or absent during simple movements, typically around three to six weeks post-injury. The primary goal transitions to rebuilding functional strength and improving the dynamic stability of the shoulder girdle, focusing heavily on the muscles surrounding the shoulder blade (scapula). Strengthening the muscles that anchor the scapula, such as the rhomboids and trapezius, helps stabilize the entire shoulder complex, reducing mechanical stress on the AC joint.
Light resistance band exercises are introduced to target the rotator cuff muscles, particularly for external rotation. By keeping the elbow bent at 90 degrees and tucked close to the side, a light resistance band is used to slowly pull the hand outward, away from the body. This movement uses very low resistance to avoid overloading the joint while training the small stabilizing muscles. Controlled strengthening improves the shoulder’s neuromuscular control during daily activities.
Scapular retraction exercises, such as seated rows with a band, are incorporated to train the muscles that pull the shoulder blades together. Sitting upright and pulling a resistance band or cable toward the chest, focusing on squeezing the shoulder blades without shrugging, helps establish a stable base for arm movement. This controlled movement reinforces correct scapular positioning, which reduces stress and motion at the AC joint.
Prone Y and T raises strengthen the middle and lower trapezius muscles. Lying face down, the arm is lifted in a ‘Y’ position (above the head) or a ‘T’ position (straight out to the side), using only body weight or light dumbbells. These movements must be slow and controlled, focusing on initiating the lift by pinching the shoulder blades and ensuring the upper trapezius does not overcompensate. This targeted strengthening supports the stability of the entire shoulder girdle, preparing it for heavier loads and more complex movements.
Advanced Phase and Return to Activity
The advanced phase of rehabilitation is initiated once the patient can demonstrate full, pain-free range of motion in all planes and the strength of the injured side is approaching parity with the uninjured side. This stage focuses on restoring the endurance, power, and functional capacity needed for a complete return to pre-injury activities, including overhead sports or heavy manual labor. Progression is strictly criteria-based, not time-based, meaning the joint must be strong enough to handle the increased load without pain.
Overhead movements are gradually introduced to re-acclimate the joint to full elevation, starting with very light resistance, such as a light overhead press or wall slides performed while standing. The emphasis remains on maintaining impeccable form, ensuring the scapula is controlled and the AC joint does not experience any grinding or pain. The resistance and duration of these exercises are increased slowly and systematically to rebuild tissue tolerance and prevent setbacks.
For individuals returning to sports that involve throwing or contact, plyometric or dynamic exercises may be introduced to train the shoulder’s ability to handle high-velocity forces. This might include medicine ball throws against a wall or rapid resistance band drills, which train the muscles to react quickly and absorb shock. The final step involves simulating the specific demands of the intended activity, such as gradually increasing weight or sport-specific training intensity, confirming the joint can withstand the required forces without pain or instability.