Anterior cruciate ligament tear (ACL)

Overview: What is an anterior cruciate ligament tear?

The anterior cruciate ligament (ACL) stabilizes the knee against anterior sliding of the shin and against rotational movements. If the ligament tears partially or completely, instability often occurs with the risk of associated injuries (e.g. meniscus, cartilage).

• Acute injury caused by twisting, braking abruptly or landing after a jump
• Partial tear (incomplete) or complete tear (complete)
• Accompanying injuries often: medial meniscus, medial ligament, bone bruises

Anatomy and function

The anterior cruciate ligament runs in the center of the knee joint and connects the thigh bone (femur) and shinbone (tibia). It consists of fiber bundles that absorb different tensile forces depending on the knee flexion.

• Primary task: Limiting the anterior translational thrust of the tibia
• Important role in rotation control (pivot mechanics)
• Interaction with collateral ligaments, menisci and muscles

Causes and risk factors

The majority of ACL tears occur without direct contact with an opponent. Rapid changes of direction, braking or unfavorable landings are typical. Contact trauma with valgus/rotational forces is also possible.

• Sports: football, handball, basketball, skiing, tennis
• Neuromuscular factors: Deficits in jumping/landing technique
• Previous injuries and inadequate trunk/hip stability
• Female gender (depending on the sport) as an epidemiological risk factor
• Inadequate warm-up or fatigue

Typical symptoms

• Acute clicking/clicking in the knee
• Sudden shooting pain and rapid swelling (hemarthrosis)
• Feeling of buckling or instability, especially under twisting loads
• Restriction of movement in the first few days
• Later: feeling of insecurity, avoidant movements

Diagnostics: Examination and imaging

Diagnosis is based on history, clinical functional testing and imaging. It is important to recognize accompanying injuries, as these have a significant impact on therapy planning.

• Clinical tests: Lachman test (sensitive), anterior drawer, pivot shift (rotational instability)
• Comparison of both knees, assessment of swelling, mobility and pain points
• Sonography for effusion assessment in the acute phase
• MRI to show ACL, menisci, cartilage, bone bruise and possible avulsion fragments
• X-ray to rule out accompanying bony injuries (Segond fracture, etc.)
• Instrumented measurement (e.g. KT-1000/2000) for quantitative laxity assessment, if appropriate

Conservative therapy: when does it make sense?

Not every ACL tear requires surgery. The aim of conservative treatment is stable, resilient knee function for everyday life, work and – depending on requirements – sport. The prerequisite is careful selection and structured rehabilitation.

• Partial rupture without pronounced instability
• Lower athletic demands or foregoing pivot/contact sports
• Older age, relevant comorbidities or surgical contraindications
• High adherence to physical therapy and willingness to adapt activities

Building blocks of conservative therapy:

• Acute management (rest, cooling, elevation, compression)
• Early function: reduction of swelling, regaining extension, painless flexion
• Targeted muscle building (quadriceps, hamstrings, hip abductors), sensorimotor training
• Gait training, technology optimization in sports, prevention programs (e.g. FIFA 11+)
• Temporary functional knee orthosis for everyday/work requirements, weigh up individually

Limitations of conservative therapy become apparent in the case of persistent instability, repeated buckling or relevant accompanying injuries (e.g. meniscus tears requiring repair). The surgical option should then be discussed.

Surgical therapy: ACL reconstruction

In cases of persistent instability, high sporting demands, combined ligament injuries or meniscus damage that requires repair, arthroscopic ACL reconstruction can be useful. The aim is to improve stability and joint protection.

• Technique: Arthroscopic reconstruction with the body's own tendons (autografts) - usually semitendinosus/gracilis (hamstrings), patellar tendon (BTB) or quadriceps tendon
• Graft selection individually based on sports profile, anatomy, previous interventions
• Additional procedure for pronounced rotational instability: anterolateral augmentation (e.g. ALL or extra-articular tenodesis) - selective indication
• Accompanying measures: meniscus suture, cartilage therapy, treatment of accompanying ligament injuries

The time of the operation is determined individually. A short period of pre-rehabilitation is often useful to reduce swelling and achieve full extension. This can prevent complications such as arthrofibrosis.

Alternative transplants such as donor tendons (allografts) are used less frequently in Germany and should be discussed in certain constellations.

Rehabilitation: phases, course and return to sport

Rehabilitation follows clear phases with function-based criteria instead of rigid calendar dates. Controlling swelling, gaining mobility, building strength and neuromuscular control are essential.

• Criteria for return-to-sport: side difference strength and jump tests if possible ≤10%, stable axle guidance, no swelling/pain, safe landing technique, psychological readiness
• Injury prevention training (prevention programs)
• Realistic goal setting – return to competition later than start training

Prognosis and possible complications

Many patients regain a high level of functionality with appropriate therapy. The course depends on the extent of the injury, accompanying injuries, adherence to therapy and the demands of the sport.

• Possible complications: limitation of movement/arthrofibrosis, re-rupture/graft failure, cyclops lesion, anterior knee pain (e.g. in BTB), thrombosis, infection (rare)
• Long-term risk: Development of cartilage damage/osteoarthritis, particularly in the event of repeated instability events or meniscus loss
• Consistent rehabilitation and prevention reduce risks, but do not replace individual follow-up monitoring

Regenerative processes: what is possible?

Biological procedures such as platelet-rich plasma (PRP) are discussed, for example to support healing in partial ruptures or after surgery. The evidence is heterogeneous. Application should only be carried out after an individual benefit-risk assessment and without false expectations.

Prevention: Protect your knees – prevent instability

• Neuromuscular training programs (e.g. landing technique, core/hip stability)
• Adequate warm-up and fatigue management
• Sport-specific technical training and appropriate footwear
• Continuous strength and balance training

Special situations

• Partial rupture: Often a conservative attempt with structured rehabilitation and follow-up
• Young people who are active in sports: High pivot/contact sports demands are more likely to be in favor of reconstruction
• Growing patients: child-friendly techniques that protect the growth plates, close planning
• Concomitant injuries: Meniscus sutures and ligament injuries affect timing and rehab
• Rotational instability (high pivot shift): If necessary, extension of the intervention to control rotation according to individual indication

Decision support: conservative or surgery?

The treatment decision should be made together. We take into account injury patterns, degree of instability, sports and professional demands, accompanying injuries and personal goals. A structured conservative attempt is often useful - surgery is considered if instability persists or relevant associated damage is present.

• Define goals: everyday life, work, leisure or competitive sports
• Objective findings: Clinical instability, MRI, instrumented measurement
• Weigh up the risk benefits: healing process, risk of complications, rehabilitation effort
• Transparent about expectations, without guarantees

When should you see a doctor?

• Large swelling and severe pain after twisting trauma
• Feeling of massive instability or repeated buckling
• Sensation of blockage, entrapment – ​​indication of meniscus lesion
• Fever or redness/warmth after the procedure
• Shortness of breath, leg swelling or pain as possible signs of thrombosis/embolism - clarify emergency situation

Your appointment in Hamburg-Winterhude

In the orthopedic practice at Dorotheenstrasse 48, 22301 Hamburg, we offer a careful clinical examination, modern imaging and clear treatment planning. Our focus is on conservative options, supplemented by surgical partner networks when medically appropriate.

We will discuss in an understandable way what you can contribute yourself - from acute measures to physiotherapy to returning to sport and work. You can easily request appointments online via Doctolib or by email.