AC joint sprain (shoulder corner joint): causes, diagnosis and therapy

Anatomy: What is the acromioclavicular joint (AC joint)?

The AC joint (acromioclavicular joint) connects the lateral end of the clavicle with the bony shoulder roof (acromion). It is a small but important sliding joint for the coordination of movements of the shoulder blade and arm.

• Stabilizing structures: AC capsule and ligaments (horizontal), coracoclavicular ligaments (CC ligaments: trapezoid and conoid ligaments; vertical stability).
• Interaction with the shoulder blade: enables fine adjustment movements for overhead activities.
• Source of pain: If the AC joint is overused or injured, it can be significantly painful.

Causes and risk factors

An AC joint sprain is usually caused by direct force on the lateral shoulder, typically when falling onto the tip of the shoulder.

• Sports: cycling, mountain biking, football, handball, ice hockey, skiing, snowboarding, martial arts.
• Everyday life: Falling on wet ground or from a ladder.
• Risk factors: lack of protection in contact sports, inadequate shoulder blade and trunk stability, previous injury to the AC joint.

Symptoms: How do you recognize an AC joint sprain?

• Acute, stabbing pain at the upper outer end of the shoulder (directly above the AC joint).
• Swelling, tenderness and occasionally a visible step displacement (“piano key phenomenon”).
• Pain when the arm is moved across the body (adduction), when placed on the affected side and during overhead movements.
• limitation of strength and movement; Keep your arm in a protective position.
• In more severe cases, visible misalignment of the collarbone.

Diagnosis: Examination and imaging

Diagnosis is based on history, clinical examination and appropriate imaging. It is important to distinguish it from a fracture of the collarbone or other shoulder injuries.

• Clinical: inspection (swelling/deformity), palpation of the AC joint, functional testing. Pain provocation e.g. B. Cross-body adduction test.
• X-ray: standard images of the shoulder; Special Zanca image to assess the AC joint. Side difference of the CC distance helpful. Stress recordings are now used selectively.
• Ultrasound: assessment of soft tissues, effusion and associated injuries.
• MRI: In case of unclear findings, severe instability, suspected concomitant injuries (e.g. disc, rotator cuff).
• Differential diagnoses: distal clavicle fracture, rotator cuff lesion, sternoclavicular joint injury, shoulder dislocation.

Rockwood severity levels

The Rockwood classification (I–VI) describes the extent of ligament injuries and misalignment. It is clinically proven and helps guide the treatment decision.

Conservative treatment: First choice for many injuries

For the common Rockwood grades I-II and selected grade III injuries, non-surgical treatment is usually methodologically sensible. The aim is to quickly relieve pain, restore function and safely return to everyday life, work and sport.

• Short-term immobilization in a Gilchrist bandage/sling (typically a few days to 1-2 weeks depending on the pain).
• Cooling, protection, pain-adapted stress; pain-relieving and anti-inflammatory measures as recommended by a doctor.
• Early physiotherapy: pendulum exercises, active movements in the pain-free area, posture training, scapula setting.
• Progressive strengthening: rotator cuff, scapular stabilizers (lower/upper trapezius, serratus anterior), core stability.
• Tape/orthosis: temporary for pain relief and proprioception.
• Everyday life/work: Screen activities are usually possible early on; physical work gradually after gain in function and freedom from pain.
• Sport: running/cycling ergometer often early; low-contact sports after 3–6 weeks; Release contact sports/overhead throws later and individually.

A cosmetic hump on the collarbone can persist despite good function. The complaint situation is crucial. Regular follow-up checks help to adjust therapy.

Surgery: When does it make sense?

Surgical stabilization is particularly recommended for severe injuries (Rockwood IV–VI). For grade III, the decision is individual and depends on instability (especially horizontal), professional/sporting requirements and the course of the symptoms under conservative therapy.

• Goals: Restoration of stability (vertical and horizontal), pain relief, safe return to strenuous activities.
• Procedure: arthroscopically assisted stabilization of the CC ligaments (e.g. suture anchors/suture button systems), suture/reinforcement of the AC capsule, if necessary additional ligament reconstruction (autograft/allograft).
• Alternative/supplement: Hook plate (usually temporary, with planned plate removal) – used selectively today.
• Accompanying measures: Treatment of intra-articular lesions (e.g. discus).
• Possible risks: infection, bleeding, nerve irritation, loss of reduction, material irritation, bone reactions (osteolysis), stiffness, persistent complaints, development of osteoarthritis.

The choice of procedure depends on the severity, tissue quality, time since injury and individual requirements. A detailed explanation of the benefits, alternatives and risks is required before every operation.

Healing process and rehabilitation

The recovery path depends on the severity and treatment. A structured rehabilitation program is crucial for a good functional outcome.

• Conservative: Pain-adapted mobilization from early on, increasing load after functional progress. Everyday life usually within a few weeks, sport gradually with a focus on stability and technique.
• Postoperatively: usually 4–6 weeks of relative immobilization with early functional therapy. Passive/assistive movements early, active strengthening from a time approved by the doctor.
• Return-to-Activity: everyday stress according to stability and strength goals; Overhead and contact sports often after 3-6 months - depending on function, pain and medical assessment.
• Physiotherapeutic focus: scapula control, rotator cuff, closed chain, sensorimotor training, posture and breathing patterns, ergonomic adjustments.
• Pain management: multimodal as needed; The aim is rehabilitation that is appropriate for the load and not overprotective.

What you can do yourself

• Cool in the first few days, pay attention to skin protection; pain-adapted protection.
• Lying sideways on the healthy side; If necessary, pillows for arm support.
• Early, pain-free movements (e.g. pendulum) to avoid stiffness - according to instructions.
• Gradual building of posture and shoulder blade control in everyday life (e.g. upright sitting position, short activation exercises).
• Pause in sports if there is a risk of contact or fall until medical clearance.
• Pay attention to warning signs (see below) and, if you are unsure, seek medical advice as early as possible.

Prevention: How to prevent it

• Sport-specific technique and fall training, especially in cycling, skiing and contact sports.
• Strengthening the rotator cuff and scapula stabilizers; Core stability.
• Sufficient warm-up and mobility training for the shoulder and thoracic spine.
• Use protective equipment where appropriate (e.g. protectors in contact sports).
• Increase stress slowly and plan for regeneration.

Possible long-term consequences and complications

Despite appropriate treatment, symptoms can persist. Honest expectations help with therapy planning.

• Chronic instability (vertical/horizontal) with pain on exertion.
• Bony, prominent clavicle (“hump”) – cosmetically noticeable, often functionally well tolerated.
• AC joint osteoarthritis or irritation of the disc.
• Muscular imbalances, scapular dyskinesia, secondary shoulder impingements.
• After surgery: Wound healing problems, material irritation or breakage, renewed instability.

When should you seek medical advice?

• Fall on the shoulder with immediate, severe pain or visible deformity.
• Numbness, tingling, cold feeling in the arm/hand or circulatory problems.
• Severe restriction of movement, pain at rest, night pain, fever or unclear swelling.
• Persistent symptoms despite initial protection or unclear findings.

What you can expect in our practice in Hamburg

In our orthopedic practice at Dorotheenstraße 48, 22301 Hamburg, you will receive a careful clinical examination, targeted imaging and a clear recommendation based on your activity level and objective stability. We pursue a conservative, function-oriented approach whenever medically possible.

• Thorough information about the Rockwood classification and therapy options without any promise of cure.
• Individual rehabilitation planning with close physiotherapeutic collaboration.
• Surgical options with clear indications, including explanation of alternatives and risks.
• Structured progress controls with functional checks and return-to-activity recommendations.

Frequently asked questions (FAQ) about AC joint rupture

Selected answers to common patient questions can be found below. We would be happy to discuss any further questions in person.