AC Joint Osteoarthritis: Causes, Symptoms, and Treatments

Introduction to AC Joint Osteoarthritis

Certain joints in the body are more prone to problems caused by normal wear and tear. Over time, the cartilage that cushions these joints begins to deteriorate, leading to a condition known as osteoarthritis, or arthrosis.

The acromioclavicular (AC) joint, located in the shoulder, is particularly susceptible to osteoarthritis, especially in middle age. Degeneration in the AC joint can result in pain and difficulty performing everyday activities.

What This Guide Covers

This guide will help you understand:

  • The structure and function of the AC joint.
  • The causes of pain and issues in the AC joint.
  • The available treatment options for managing this condition.

Anatomy of the AC Joint: Understanding Its Role

The shoulder joint is composed of three bones:

  • Scapula (shoulder blade): Forms the back part of the shoulder.
  • Humerus (upper arm bone): Connects the shoulder to the arm.
  • Clavicle (collarbone): Links the shoulder to the chest.

The acromion, part of the scapula, extends to form the roof of the shoulder and connects to the clavicle, creating the acromioclavicular (AC) joint.

How the AC Joint Works

  • The AC joint, like other joints, allows flexibility while connecting two bones.
  • The ends of the acromion and clavicle are covered in articular cartilage, which:
    • Provides a smooth, rubbery surface for easy gliding of bones.
    • Acts as a shock absorber to reduce stress during movement.

Unique Characteristics of the AC Joint

Unlike highly mobile joints such as the knee or ankle, the AC joint:

  • Requires minimal movement to function.
  • Shifts only slightly to support shoulder motions, ensuring the shoulder moves freely while maintaining stability.

Understanding the structure and limited movement of the AC joint is crucial for identifying how wear and tear can lead to osteoarthritis.

Causes of AC Joint Osteoarthritis: Why Does It Develop?

The AC joint endures constant use and strain, making it highly susceptible to wear and tear. Over time, this repetitive stress leads to degeneration of the joint, resulting in osteoarthritis.

Common Causes of AC Joint Degeneration

  1. Repetitive Shoulder Use:

    • Frequent overhead movements place significant stress on the AC joint.
    • Activities such as weightlifting and heavy lifting increase the likelihood of developing osteoarthritis, often at a younger age.

  2. Previous Injuries:

    • AC Joint Separation:
      • This common injury occurs when the shoulder sustains direct trauma, such as falling on it.
      • While the joint may heal, long-term degeneration from the injury often results in painful osteoarthritis years later.

By understanding these causes, individuals can identify risk factors and take preventive measures to minimize strain on the AC joint.

Symptoms of AC Joint Osteoarthritis

The symptoms of AC joint osteoarthritis often develop gradually and can worsen over time. Early recognition of these signs is essential for effective management and treatment.

Key Symptoms

  1. Pain and Tenderness:

    • Pain typically begins in the front of the shoulder near the AC joint.
    • Discomfort often increases when the arm is brought across the chest, as this movement compresses the joint.

  2. Radiating Pain:

    • The pain may extend to other areas, including the shoulder, front of the chest, and neck.
    • This makes the condition feel more diffuse and harder to pinpoint.

  3. Visible Changes:

    • In cases where the joint has been previously injured, a noticeable bump may appear over the affected AC joint compared to the unaffected side.

  4. Clicking or Snapping Sounds:

    • The joint may produce clicking or snapping noises during movement, indicating irregular motion or structural changes.

Understanding these symptoms can help in the early diagnosis and prompt treatment of AC joint osteoarthritis.

Diagnosis of AC Joint Osteoarthritis: What to Expect

Accurate diagnosis of AC joint osteoarthritis involves a combination of medical history, physical examination, and imaging tests to confirm the condition and assess its severity.

Steps in Diagnosis

  1. Medical History

    • Your doctor will ask detailed questions about your symptoms and how they impact your daily life.
    • You may be asked about past shoulder injuries and to rate your pain on a scale of 1 to 10.

  2. Physical Examination

    • Tenderness: The AC joint is usually tender upon touch.
    • Compression Test:
      • The doctor gently pulls your arm across your chest to compress the joint.
      • Pain during this test indicates issues with the AC joint.
    • Local Anesthetic Test:
      • A local anesthetic like lidocaine may be injected into the AC joint.
      • If the pain subsides temporarily, the AC joint is confirmed as the source of discomfort.

  3. Imaging Tests

    • X-rays:
      • X-rays help identify joint degeneration, including:
        • Narrowing of the joint space.
        • Bone spurs around the joint.

By combining these diagnostic methods, doctors can confirm AC joint osteoarthritis and determine the best treatment approach.

Treatment Options for AC Joint Osteoarthritis

Treatment for AC joint osteoarthritis focuses on relieving pain, reducing inflammation, and restoring shoulder function. Options range from nonsurgical approaches to surgical intervention, depending on the severity of the condition.

Nonsurgical Treatment

Initial management typically includes:

  1. Rest and Medication

    • Resting the shoulder and avoiding activities that aggravate pain.
    • Anti-inflammatory medications, such as aspirin or ibuprofen, to reduce pain and inflammation.

  2. Rehabilitation Program

    • A physical or occupational therapist may guide a program focused on improving strength and flexibility.

  3. Cortisone Injections

    • If pain persists, cortisone may be injected into the joint.
    • Benefits:
      • Cortisone is a powerful anti-inflammatory agent that provides temporary but effective pain relief.

Surgical Treatment

If nonsurgical methods do not provide relief, surgery may be recommended.

Resection Arthroplasty

  • Procedure:
    • The last half-inch of the clavicle is removed to create space between the acromion and the end of the clavicle.
    • Scar tissue forms as the area heals, replacing the joint and preventing the bone ends from rubbing together.
    • This scar tissue allows the limited movement required by the AC joint.
  • Approaches:
    • Open Surgery:
      • Performed through a two-inch incision over the joint.
    • Arthroscopic Surgery:
      • Minimally invasive, using a slender tool with a tiny camera to perform the procedure through a small incision.

Conclusion

For mild to moderate cases of AC joint osteoarthritis, nonsurgical treatments like rest, medication, and therapy are often sufficient to manage symptoms. However, for severe or persistent cases, resection arthroplasty offers an effective surgical solution, with options for minimally invasive techniques ensuring quicker recovery and reduced discomfort.

Rehabilitation After Treatment for AC Joint Osteoarthritis

Rehabilitation is a key component of recovery, whether you undergo nonsurgical treatment or surgery. A well-structured program helps restore shoulder function, improve strength, and manage symptoms effectively.

Nonsurgical Rehabilitation

If surgery is not required, your rehabilitation will focus on restoring range of motion and building strength in a gradual, controlled manner:

  1. Range-of-Motion Exercises:

    • Begin exercises as pain decreases.
    • Movements are initially limited to keeping the arm below shoulder level to avoid aggravating the joint.

  2. Strengthening Program:

    • Progress to strengthening exercises for the rotator cuff and shoulder blade muscles.
    • These muscles play a critical role in stabilizing the shoulder and ensuring smooth movement.

  3. Symptom Management:

    • The goal is to regain normal shoulder motion and learn techniques to control symptoms during daily activities.

  4. Transition to a Home Program:

    • Most patients can move to a home-based program within four to six weeks, allowing continued progress independently.

Conclusion

Rehabilitation without surgery involves a gradual approach, beginning with pain-free movements and advancing to strength-building exercises. Consistent adherence to the program helps restore shoulder mobility, improve strength, and minimize the risk of future discomfort.

Rehabilitation After Surgery for AC Joint Osteoarthritis

Recovery after surgery requires a carefully managed rehabilitation program to restore shoulder function while protecting the healing tissues. The timeline and progression of therapy vary based on the type of surgery performed.

Initial Recovery Phase

  1. Support and Protection:

    • A sling may be used for the first few days to support and protect the shoulder.

  2. Early Pain Management:

    • The focus during the initial therapy sessions is to reduce pain and swelling through:
      • Ice therapy to manage inflammation.
      • Electrical stimulation treatments to ease discomfort.
      • Massage and manual techniques to relieve muscle spasms.

Rehabilitation After Arthroscopic Resection

  • Faster Recovery Timeline:

    • Therapy can progress quickly following minimally invasive arthroscopic surgery.

  • Range-of-Motion Exercises:

    • Early sessions focus on restoring motion to the shoulder.

  • Strengthening and Stretching:

    • Active stretching and strengthening exercises are gradually introduced.
    • Care is taken to avoid overloading the joint early in recovery.

Rehabilitation After Open Surgery

  • Slower Recovery Timeline:

    • Recovery is more gradual when surgery involves cutting through shoulder muscles.

  • Passive Exercises (Weeks 0–2):

    • Exercises begin approximately two weeks after surgery.
    • During passive exercises, the therapist moves your shoulder joint while your muscles remain relaxed.
    • You may be taught how to perform passive exercises at home.

  • Active Exercises (Weeks 4–6):

    • Active range-of-motion exercises involve using your own muscles to move the joint.
    • Light isometric strengthening exercises may also begin, which activate the muscles without stressing the joint.

  • Advanced Strengthening (After Week 6):

    • Strengthening exercises focus on improving the rotator cuff and shoulder blade muscles.
    • Retraining these muscles ensures smooth movement and keeps the humerus properly aligned in the socket.

Functional Training and Injury Prevention

  1. Work and Sport-Specific Training:

    • Exercises mimic work tasks or sports movements to prepare the shoulder for real-life activities.

  2. Stress Reduction Strategies:

    • Your therapist will teach techniques to avoid placing excessive stress on the shoulder during daily tasks.

  3. Preventing Future Problems:

    • Before completing therapy, you will learn ways to minimize the risk of recurrence, such as proper posture and body mechanics.

Conclusion

Rehabilitation after surgery for AC joint osteoarthritis is a gradual process tailored to the type of procedure performed. With consistent adherence to the rehabilitation plan, patients can regain strength, mobility, and function, allowing for a return to normal activities and reduced risk of future issues.

 

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