Acromioclavicular Joint

 

Introduction

The shoulder is one of the most mobile joints in the human body, allowing a wide range of movements essential for daily activities. Within this complex structure lies a smaller but significant joint known as the acromioclavicular (AC) joint. Despite its size, it plays a key role in shoulder function and can be a source of discomfort when affected by injury, overuse, or degeneration.
This article explores the anatomy, biomechanics, common issues, and management strategies for AC joint conditions, with a focus on the role of ultrasound-guided cortisone injections offered at Joint Injections.

Anatomy of the Acromioclavicular Joint

Structure

The AC joint is located at the top of the shoulder, where the acromion (part of the scapula or shoulder blade) meets the clavicle (collarbone). This junction is supported by several ligaments, including:

  • Acromioclavicular ligament — stabilises the joint directly.
  • Coracoclavicular ligaments (trapezoid and conoid) — provide additional stability.

The joint is lined with cartilage and contains a thin layer of synovial fluid, allowing smooth movement between the bones.

Function

While the AC joint does not have the same large range of motion as the main shoulder (glenohumeral) joint, it plays a crucial role in overhead and across-the-body movements. It acts as a pivot point, enabling the scapula to rotate and adjust during arm elevation.

Biomechanics and Role in Shoulder Movement

Movements involving the AC joint are often subtle yet essential. During arm elevation, the scapula must rotate upward, a movement facilitated partly by the AC joint. Without proper function of this joint, reaching overhead, lifting, or even lying on the affected side can become challenging.

Common Conditions Affecting the AC Joint

1. Osteoarthritis

AC joint osteoarthritis can develop due to natural wear and tear over time. Cartilage breakdown leads to bone-on-bone contact, which may be associated with localised tenderness and reduced function.

2. Injury or Trauma

A direct blow to the shoulder, such as from a fall, can cause an AC joint sprain or dislocation. This is common in contact sports or after accidents.

3. Overuse Syndromes

Repetitive overhead activities, such as weightlifting or manual labour, can put strain on the AC joint, leading to inflammation.

4. Distal Clavicle Osteolysis

Seen often in athletes, this condition involves the breakdown of bone at the end of the clavicle due to repeated stress.

Symptoms of AC Joint Issues

Although symptoms can vary depending on the cause, individuals may experience:

  • Localised pain at the top of the shoulder.
  • Discomfort during overhead or cross-body movements.
  • Tenderness on palpation of the joint.
  • In some cases, visible swelling or a bony prominence.

Diagnosis

A clinician will assess the AC joint through:

  • Medical history — reviewing any injuries, activities, or underlying conditions.
  • Physical examination — checking for tenderness, swelling, or restricted movement.
  • Imaging — such as ultrasound to identify joint changes or injuries.

Management of AC Joint Conditions

Activity Modification

Reducing or avoiding activities that aggravate symptoms can allow the joint to settle.

Ultrasound-Guided Cortisone Injections at Joint Injections

For cases where symptoms persist, ultrasound-guided cortisone injections can be considered. At Joint Injections, this involves:

  • Using ultrasound imaging to precisely locate the AC joint.
  • Delivering cortisone (a corticosteroid) directly into the joint space to target inflammation.
  • Ensuring accuracy and minimising discomfort through image guidance.

This targeted approach is designed to address inflammation in the joint while avoiding surrounding structures.

Mechanism of Cortisone in AC Joint Conditions

Cortisone is a synthetic corticosteroid that works by:

  1. Reducing inflammatory mediators — lowering the activity of substances in the body that promote inflammation.
  2. Decreasing swelling in the joint capsule — which can improve movement.
  3. Altering nerve activity — potentially reducing localised pain sensitivity.

When administered under ultrasound guidance, the precision of the injection is maximised, potentially improving outcomes.

Why Choose Joint Injections for AC Joint Management

  • Specialist clinicians experienced in musculoskeletal care.
  • Ultrasound-guided precision for all injections.
  • Individualised approach — considering your lifestyle, activities, and needs.
  • Comfort-focused procedures designed with patient care in mind.

Living with an AC Joint Condition

With the right guidance, many individuals can maintain good shoulder function and minimise the impact of AC joint issues. Strategies may include:

  • Adjusting activity intensity.
  • Incorporating shoulder-strengthening exercises.
  • Seeking early assessment when symptoms develop.

Conclusion

The acromioclavicular joint, while small, plays a significant role in shoulder mobility and function. Understanding its anatomy, potential issues, and available management options can empower individuals to make informed decisions about their shoulder health. At Joint Injections, the focus remains on precise, ultrasound-guided care tailored to each person’s needs.

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