AC joint osteoarthritis

What is AC joint osteoarthritis?

AC joint arthrosis is the wear and tear of the cartilage surfaces in the joint between the end of the clavicle and the acromion. This small but loaded joint controls fine movements of the shoulder, transmits forces and is heavily stressed by overhead and pressure loads. Cartilage wear leads to friction, inflammation of the joint lining (synovitis) and bony attachments (osteophytes) - the result is pain and restricted movement.

Anatomy and function

The acromioclavicular joint connects the outer end of the clavicle to the acromion. It is stabilized by a firm joint capsule and ligaments (including the coracoclavicular ligaments). Although the range of motion is small, the AC joint is critical for fine-tuning scapula and upper arm movements. Stress peaks occur during overhead activities, push-ups, bench presses and when carrying heavy loads.

• Location: upper, lateral pole of the shoulder – tender with arthrosis
• Function: Power transmission between arm/scapula and torso
• Special feature: a common source of local shoulder pain, even in young, physically active people

Causes and risk factors

AC joint arthrosis usually occurs as a result of long-term stress or repeated microtraumas. Early wear and tear can also occur after injuries.

• Repetitive overhead and pressure loads (e.g., crafts, painting, bench press, CrossFit, throwing and contact sports)
• Previous injuries: AC joint sprain (Rockwood/Tossy), clavicle end injuries
• Distal clavicle osteolysis (especially during intensive strength training)
• Natural age-related wear and tear
• Poor posture and muscular imbalance in the shoulder girdle

Typical symptoms

• Pinpoint pain at the top of the shoulder above the AC joint, often tender
• Pain provocation when crossing the arm in front of the body (cross-body adduction)
• Discomfort with overhead movements, push-ups, bench presses and carrying bags
• Night pain when lying on the affected side
• Occasional clicking or rubbing, sometimes swelling over the joint

The symptoms can radiate to the side of the upper arm. Irritation of the bursa under the acromion (subacromial) often occurs concurrently and worsens the symptoms.

Diagnostics: targeted and gentle

Diagnosis is based on history, physical examination and imaging tests. It is important to distinguish it from other causes of shoulder pain, such as tendon problems in the rotator cuff or omarthrosis (wear and tear in the large shoulder joint).

• Clinical tests: local tenderness over the AC joint, cross-body adduction test, O’Brien test
• X-ray: special Zanca image shows joint space, osteophytes, sclerosis; Axillary image to assess alignment
• Ultrasound: assessment of bursa, tendons; Possibly joint effusion
• MRI: in case of unclear findings or resistance to therapy, for differentiated visualization of cartilage, capsule, and accompanying lesions
• Diagnostic injection: temporary elimination of pain using local anesthetic in the AC joint as evidence of the pain generators

Conservative treatment – ​​the first step

Most patients benefit from structured, conservative therapy. The aim is to relieve pain, reduce inflammation and improve shoulder girdle mechanics in order to relieve the AC joint.

• Activity adaptation: temporary reduction of overhead and pressure loads; Technique and exercise adjustments for strength training (e.g. tighter grip, shallower depth for bench presses)
• Medication: if necessary, short-term anti-inflammatory painkillers (NSAIDs) - after an individual risk-benefit assessment
• Physiotherapy: posture training, strengthening of the scapular stabilizers (m. serratus anterior, lower/upper trapezius), rotator cuff; Mobilization of the thoracic spine
• Stretching: posterior capsule and chest muscles (posterior capsule stretch, pectoralis stretch)
• Manual therapy and soft tissue-oriented techniques for pressure relief
• Cooling in acute phases of irritation, warmth in case of muscular tension
• Taping/application of a soft shoulder support during stress phases

It is important to gradually build up the load: first stabilize movement patterns that cause little discomfort, then specifically increase strength and endurance. As a rule, conservative treatment attempts should be carried out consistently over several weeks to months.

Targeted injections: options with a sense of proportion

Injections can bridge symptoms or break through an irritable state. They do not replace active therapy, but can usefully complement it. The application is preferably carried out using ultrasound control in order to increase accuracy and safety.

• Cortisone + local anesthetic: proven option for acute inflammation; Effects often rapid, duration variable. Risks of repeated administration: skin/fatty tissue atrophy, rarely infection. Numbers and distances are carefully limited.
• Hyaluronic acid: partly used for the AC joint; Evidence mixed, benefits individual.
• PRP (platelet-rich plasma): regenerative option with growing but still heterogeneous data; is used cautiously and after informed consent, especially a. in treatment-resistant cases.

Which form of injection makes sense in each individual case is decided together based on the clinical examination, previous illnesses and treatment goals.

Surgical options – when conservative is not enough

If the symptoms persist despite adequate conservative therapy and significantly affect everyday life or sports, surgery can be considered. The aim is to achieve pain-free resilience by eliminating painful joint surfaces without endangering stability.

• Arthroscopic distal clavicle resection (Mumford procedure): removal of 5–10 mm of the outer end of the clavicle, preservation of the stabilizing ligaments. In many cases combined with treatment of accompanying subacromial irritations - only if indicated.
• Open approach: rarely necessary, e.g. B. in the case of severe deformities or previous operations.
• Adjunctive treatments: Address bursitis or bony growths if they clearly contribute to the symptoms.

As with any procedure, there are general risks such as bleeding, infection, thrombosis, injury to adjacent structures or persistent discomfort. Realistic expectation management is essential; Guarantees are not possible.

Rehabilitation and course

According to a conservative approach, the return to sport and work takes place gradually. Decisive markers are freedom from pain in everyday life, good shoulder blade control and sufficient strength endurance.

• After arthroscopic Mumford surgery: short-term immobilization in an arm sling to reduce pain, early functional physiotherapy from day 1-2, everyday activities usually possible after 1-2 weeks.
• Sport: light ergometer/lower body dominant training possible early; Targeted shoulder strength training often after 6-8 weeks, contact sports and heavy lifting often after 10-16 weeks - varies from person to person.
• Occupation: Office work possible after a few days, physical work after several weeks depending on the strain.

The healing process is individual. Structured aftercare with clear exercise plans and stress levels increases the chance of good functional recovery.

Prevention and self-management

• Technique optimization for pressure exercises: tighter grip, neutral dumbbell position, pain-free range of motion
• Train shoulder blade control: serratus and trapezius exercises, rotator cuff
• Regular stretching of the chest muscles and posterior shoulder capsule
• Progressive increase in load instead of sudden jumps in intensity
• Workplace ergonomics and load distribution in everyday life
• Take an early break if you have acute, localized shoulder pain

Differentiation from other shoulder diseases

Not all shoulder pain at the top of the joint is AC joint arthrosis. There are often additional or alternative causes that should be specifically treated.

• Shoulder joint osteoarthritis (omarthrosis) – wear and tear of the glenohumeral joint
• Subacromial impingement and bursitis
• Tendon irritation or rotator cuff tears
• Consequences of instability (e.g. Bankart, Hill-Sachs lesion) in younger patients
• Labrum injuries (e.g. SLAP lesion) during throwing and overhead sports
• Cervical causes (cervical spine) radiating into the shoulder

Your orthopedic care in Hamburg

In our practice at Dorotheenstrasse 48, 22301 Hamburg, we provide you with structured advice on the diagnosis and treatment of AC joint arthrosis. Our focus is on individual, conservative therapy planning with clear exercises and everyday recommendations. Injections and – if necessary – surgical options are discussed transparently. You can easily book appointments online or request them by email.

When medical evaluation makes sense

• Persistent shoulder pain lasting more than 4-6 weeks despite rest
• Significantly increasing discomfort or pain at night when resting
• Acute pain after a fall/trauma with swelling or visible deformity
• Accompanying general symptoms such as fever, redness, severe overheating
• Newly occurring loss of strength or sensory disturbances