Introduction
The anterior cruciate ligament (ACL) injury is one of the most common and serious knee injuries. This injury particularly affects athletes but also occurs in recreational and physically active individuals. The ACL is crucial for knee stability and normal functioning in both sports and daily activities. Every year, hundreds of thousands of people worldwide experience ACL injuries, and many require surgery and long-term rehabilitation. In this blog, we explain what the ACL is, how injuries occur, what symptoms to look for, how diagnosis is made, and the treatment and rehabilitation options available.
What is the ACL and why is it important?
The knee is the most complex joint in the human body, consisting of bones, cartilage, ligaments, and muscles. Among the ligaments, the ACL is one of the four key stabilizers of the knee.
Functions of the ACL:
- Prevents the tibia from sliding forward relative to the femur
- Provides stability during rotations, sudden changes of direction, and landings
- Prevents the knee from ‘giving way’ during sudden movements
- Enables safe performance of sports activities such as football, basketball, handball, skiing, and tennis.
How does an ACL injury occur?
ACL injuries most often occur in athletes but can also happen during everyday movements. The most common causes are sudden changes of direction, landing on one leg, rotational movements with a fixed foot, and direct contact with another player. More than 70% of ACL injuries occur without direct contact, usually during landings or changes of direction. Female athletes are 2–3 times more likely to suffer ACL injuries than male athletes due to anatomical, hormonal, and biomechanical differences. Sports with the highest incidence include football, basketball, handball, skiing, and American football.
Symptoms of ACL injury
Typical symptoms include:
- A popping sound or sensation at the moment of injury
- Sudden and severe pain
- Rapid swelling within a few hours
- Knee instability, the feeling that it is ‘giving way’
- Reduced range of motion and difficulty bearing weight on the leg.
Diagnosis of ACL injury
Diagnosis is made using a combination of physical tests and imaging methods.
Clinical tests:
- Lachman test
- Pivot-shift test
- Anterior drawer test
Imaging methods:
- MRI (gold standard)
- X-ray (to rule out fractures)
- Ultrasound (less precise, supplementary).
Treatment options
Treatment depends on the patient’s age, activity level, and goals.
Conservative treatment (non-surgical):
- Recommended for less active individuals
- Focus on strengthening muscles and improving stability
- Risk of recurrent injuries and meniscus damage remains
Surgical treatment (ACL reconstruction):
- Most common choice for athletes
- Involves ligament reconstruction using grafts (hamstrings, patellar tendon, or donor tissue)
- Requires a long rehabilitation process of 6–12 months.
Rehabilitation process
Rehabilitation is the most important part of recovery. Without it, surgery alone is not sufficient.
Phases of rehabilitation:
- Acute phase (0–2 weeks): pain and swelling reduction, regaining range of motion, quadriceps activation
- Early phase (2–6 weeks): walking without crutches, proprioception exercises, gradual strengthening
- Middle phase (6–12 weeks): strength training, stability exercises, low-impact cardio
- Late phase (3–6 months): plyometrics, agility, sport-specific movements
- Return to sport (6–12 months): testing, controlled sport drills, supervised return to competition.
Prevention of ACL injuries
Although not all injuries can be prevented, proper training significantly reduces risk:
- Strengthening quadriceps, hamstrings, and hip muscles
- Balance and proprioception exercises
- Correct landing techniques
- Preventive programs such as FIFA 11+ reduce ACL injury risk by up to 50%.
Psychological aspect of recovery
Fear of re-injury is common after ACL injuries. Successful rehabilitation must include psychological preparation, progressive exposure to sports movements, and continuous support from therapists and coaches. Mental readiness often determines return-to-sport success more than physical readiness.
Conclusion
ACL injury is a serious condition requiring timely diagnosis, proper treatment, and structured rehabilitation. With professional guidance and discipline, a full return to sports and daily activities is possible. At Knee Rehab, we provide expert advice, exercise programs, and professional support to help you achieve complete recovery.