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Home » Anatomy » Acromioclavicular Joint: Structure, Function, and Injuries

Acromioclavicular Joint: Structure, Function, and Injuries

In this article we are going to discuss about the acromioclavicular joint. It is a important part of a shoulder complex. The acromioclavicular (AC) joint is a joint that connects the acromion to the clavicle. A synovial joint has a lining of tissue that produces fluid to lubricate the joint. The AC joint allows for a small amount of movement, such as gliding and rotation.. It usually involves in providing stability and limited range of motion. It is also a main shock absorber of shoulder complex.

Structure of the AC Joint

Two bones, the acromion and the clavicle, make up the AC joint. The acromion is a bony projection that forms the highest point of the shoulder. The clavicle is a long bone that runs from the breastbone to the shoulder joint. It has flat articulating surfaces due to which It is classified as a plane joint.

A number of ligaments stabilize the AC joint. The acromioclavicular ligament is the main ligament that connects the acromion and the clavicle. The coracoclavicular ligament complex is a group of ligaments that connect the coracoid process, a small bony projection on the front of the scapula, to the clavicle.

Function of the AC Joint

The main functions of the AC joint include:

Shock Absorption

The AC joint acts as a shock absorber, dissipating forces that are transmitted through the upper limb during activities such as lifting, throwing, or carrying heavy loads.

Stability and Range of Motion

The joint provide controlled movement of the scapula and clavicle, facilitating shoulder mobility and maintaining proper positioning of the shoulder complex during various activities like overhead activities, combing etc.

Injuries to the AC Joint

In a number of ways, falls, direct blows to the shoulder, and overuse can injure the AC joint. The ligaments that stabilize the joint tear, causing an acromioclavicular separation, which is the most common injury to the AC joint.

An acromioclavicular separation is classified into three grades, based on the severity of the injury:

  • Grade I: The ligaments are stretched but not torn.
  • Grade II: The ligaments are torn, but the clavicle does not move out of place.
  • Grade III: The ligaments are torn and the clavicle moves out of place.

Grade I and II acromioclavicular separations can usually be treated with rest, ice, compression, and elevation (RICE). Grade III acromioclavicular separations may require surgery to repair the ligaments and stabilize the joint.

Symptoms of AC Joint Injuries

The symptoms of an AC joint injury can vary depending on the severity of the injury. Common symptoms include:

  • Pain in the shoulder
  • Swelling in the shoulder
  • Bruising in the shoulder
  • Difficulty moving the shoulder
  • A popping or clicking sound in the shoulder
  • A feeling of instability in the shoulder

Diagnosis of AC Joint Injuries

A doctor usually diagnoses an AC joint injury based on a physical examination and X-rays. In some cases, the doctor may order an MRI to confirm the diagnosis.

Treatment of AC Joint Injuries

The treatment of AC joint injuries depends on the severity of the injury. Rest, ice, compression, and elevation (RICE) are use to treat Grade I and II acromioclavicular separations.  Grade III acromioclavicular separations may require surgery to repair the ligaments and stabilize the joint.

Recovery from AC Joint Injuries

The recovery time from an AC joint injury varies depending on the severity of the injury. Grade I and II acromioclavicular separations usually heal within 4-6 weeks. Grade III acromioclavicular separations may take 6-12 months to heal.

Prevention of AC Joint Injuries

  • Warming up before participating in sports or activities that involve overhead movements.
  • Wearing protective gear, such as shoulder pads, when participating in sports or activities that involve contact.
  • Avoiding falls and direct blows to the shoulder.

Conclusion

The acromioclavicular joint is a joint that connects the acromion and the clavicle. It allows for a small amount of movement and helps to stabilize the shoulder joint. AC joint injuries can occur in a number of ways, and the treatment depends on the severity of the injury.

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