The shoulder is one of the largest and most complex joints in the body, where many muscles act to provide the widest range of motion of any part of the body. This flexibility is also what makes the shoulder prone to instability and injury.
The shoulder joint is formed where the humerus (upper arm bone) fits into the scapula (shoulder blade), like a ball and socket. The clavicle (collarbone) extends across the front of the shoulder from the sternum to the scapula and helps stabilize the shoulder’s movements.
Acromioclavicular Joint Injuries – Acute & Chronic (AC Joint Injuries)
WHAT IS THE AC JOINT AND AC JOINT INJURY?
The acromioclavicular, or AC joint is a joint in the shoulder where two bones meet. One of these bones is the collarbone (clavicle) and the second bone is part of the shoulder blade (scapula), which is the big bone behind the shoulder that also forms part of the shoulder joint. The portion of the shoulder blade that meets the clavicle is known as the acromion. An AC joint injury occurs when there is injury to the top of the shoulder, where the acromion meets the clavicle.
The type of shoulder separation depends on how much you tear the AC joint or coracoclavicular (CC) ligaments that hold the joint in place. There are 3 types of AC joint injuries:
- Type I
There is a sprain injury of the AC ligament, but there is no complete tear and both AC and CC ligaments are intact.
- Type II
The AC ligament is torn, and there is little or no tear to the CC ligament.
- Type III
Both the AC and CC ligaments are torn.
- Type IV
Both the AC and CC ligaments are completely torn. In this case, the collarbone separates from the end of the shoulder blade.
Common AC joint injuries include arthritis, fractures and separations.
WHAT ARE THE SYMPTOMS OF AN AC JOINT INJURY?
Common symptoms of an AC joint injury include:
- Swelling and tenderness over the AC joint
- A visible bump above the shoulder
- A popping sound or feeling whenever you move your shoulder
- Loss of strength and motion in your shoulder
- Discomfort with daily activities that involving the AC joint such as lifting objects overhead, carrying heavy objects
WHAT ARE THE CAUSES AND RISK FACTORS OF AN AC JOINT INJURY?
Risk factors of an AC joint injury include:
- Age: If you are 35 years and younger, your chances of suffering from an AC joint injury are higher
- Gender: Males have higher risk of suffering from an AC joint injury
- Sports: People participating in activities such as football, hockey and biking have higher risk
- Repetitive overhead motions such as weightlifting, construction work, painting
- Suffering from trauma to the AC joint such as during a motor vehicle crash
WHAT IS THE DIAGNOSIS OF AN AC JOINT INJURY?
Your doctor will first check on the medical history of the injury, before conducting a physical examination of your shoulder. Your doctor may also take an x-ray of the shoulder to see the severity of the damage and make sure you have not fractured your collarbone.
WHAT ARE THE TREATMENT OPTIONS FOR AN AC JOINT INJURY?
The main aims of the treatment for an AC joint injury are to manage pain, and to allow the torn ligaments to heal.
For Types I to III AC joint injury, nonsurgical treatments can help. These include:
- Resting and icing the shoulder
- Putting your arm in a sling to decrease motion and hold the shoulder in place
- Taking NSAIDs, such as ibuprofen or naproxen, to help with pain
- Physiotherapy- doing range of motion exercises to increase joint mobility and flexibility of the shoulder
For Type IV AC joint injury, surgery may be suggested by your doctor.