An AC joint sprain is a common shoulder injury, often resulting from sudden impacts or falls. Understanding this injury, including its location, causes, and symptoms, is crucial for proper recognition and care.
Understanding the AC Joint and Sprains
The acromioclavicular (AC) joint is a small but active joint located at the top of the shoulder, connecting the collarbone (clavicle) to a part of the shoulder blade called the acromion. This joint facilitates shoulder movement, enabling scapular rotation and arm movements like overhead lifting. It also transmits forces from the upper limb to the skeleton.
A sprain is an injury to ligaments, which are strong, fibrous tissues connecting bones. An AC joint sprain, therefore, is an injury where the ligaments that support the acromioclavicular joint are stretched or torn. The severity of an AC joint sprain can range from a minor stretch to a complete tear of these stabilizing ligaments.
Causes and Recognizable Symptoms
AC joint sprains commonly result from direct impacts or excessive force applied to the shoulder. Frequent causes include falls directly onto the shoulder, collisions in contact sports (e.g., football, rugby, hockey), or falling onto an outstretched hand. These incidents can suddenly push the shoulder blade away from the collarbone, stretching or tearing the supporting ligaments.
Individuals with an AC joint sprain often experience pain at the top of the shoulder, which can feel localized or spread across the shoulder area. Swelling, bruising, and tenderness over the joint are common symptoms. Depending on the injury’s severity, a visible bump or deformity may appear at the top of the shoulder, indicating that the bones have moved due to torn ligaments. Movement of the arm, especially overhead lifting or reaching across the body, can intensify the pain, and shoulder movement may become limited.
Diagnosis and Severity Classification
Medical professionals diagnose an AC joint sprain through a physical examination and imaging studies. During the examination, the doctor assesses pain location, checks for tenderness over the AC joint, and evaluates the shoulder’s range of motion. They may also look for any visible deformities or bulges.
X-rays rule out fractures and assess joint alignment and stability. Specialized views, like a Zanca view, may be used for better visualization. AC joint sprains are classified using a grading system, most commonly the Rockwood classification, which has six grades based on the extent of ligament damage and joint displacement.
- Grade I: Minor ligament stretching, no joint separation.
- Grade II: Partial acromioclavicular ligament tear, some joint misalignment.
- Grade III: Complete tear of acromioclavicular and coracoclavicular ligaments, noticeable joint separation.
- Higher grades (IV-VI): More severe collarbone displacement.
Treatment Paths
Treatment for an AC joint sprain depends on the injury’s severity. For lower-grade sprains (Grades I and II), conservative management is effective. This approach includes rest, applying ice to reduce swelling and pain, and using anti-inflammatory medications.
A sling might be recommended for comfort and to immobilize the joint for a short period, usually one to two weeks, to support healing. Early physical therapy is often initiated once initial pain subsides to help restore movement and prevent stiffness.
Higher-grade sprains (Grade III and above) may also be managed conservatively, though the decision for Grade III can be more nuanced. However, severe cases, particularly Grades IV through VI, often require surgical intervention to reposition the joint and repair the torn ligaments. Surgical options might include reconstructing the ligaments using grafts or sutures. The treatment plan is tailored to the individual, considering their activity level and the specific nature of their injury.
Recovery and Rehabilitation
The recovery timeline for an AC joint sprain varies based on its severity. Grade I sprains resolve within one to two weeks, with patients returning to normal activities once pain subsides and full range of motion is restored. Grade II sprains take three to six weeks for recovery, involving a progression from pain management to gradual rehabilitation exercises. Grade III injuries managed without surgery may require six to twelve weeks to heal, necessitating a longer period of initial immobilization and more extensive rehabilitation.
Physical therapy is a key part of the recovery process for all grades of AC joint sprains. It focuses on regaining strength, flexibility, and the full range of motion in the shoulder. Exercises often begin gently, progressing to include resistance training to improve shoulder stability.
For cases requiring surgery, recovery can extend to four to six months, including several weeks of immobilization followed by a structured rehabilitation program. Returning to normal activities or sports should be a gradual process, guided by pain levels and the restoration of function, to help prevent re-injury.