ACL injury
Last updated: 10 Feb. 2026
Reviewed by: Specialist doctors from the Elfcare quality team
Have you ever twisted your knee during a sudden turn or jump and felt an immediate “pop” followed by swelling or instability? That could be a sign of an ACL injury, one of the most common ligament injuries affecting active adults and athletes alike.
The anterior cruciate ligament (ACL) plays a key role in keeping your knee stable. When it’s stretched or torn, even simple movements, like walking downhill or turning quickly, can feel uncertain.
Early recognition and preventive care can make all the difference. Elfcare’s philosophy focuses on understanding what’s happening inside your body early, so you can act with confidence and protect your long-term joint health.
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What is an ACL injury?
The ACL is one of four major ligaments connecting your thighbone to your shinbone. It sits deep inside the knee joint, controlling forward and rotational movement.
An ACL injury happens when this ligament is overstretched or torn, most often during sudden stops, pivots, or awkward landings. In sports like football, basketball, skiing, or even quick changes in direction during workouts, the ACL is under constant stress.
A partial tear may cause mild pain or looseness, while a complete tear can make the knee unstable and difficult to bear weight on. Over time, untreated ACL injuries can increase the risk of cartilage damage and early osteoarthritis.
Symptoms of an ACL injury
Common ACL injury symptoms include:
A sudden “pop” sound or sensation in the knee
Immediate pain and swelling
Knee instability or “giving way” when walking or turning
Difficulty bending or straightening the knee fully
Tenderness along the joint line
Some people may feel the pain subside after a few days and assume it has healed. However, without proper evaluation, underlying instability may persist and affect long-term knee health.
What causes an ACL injury?
ACL injuries are often linked to a combination of movement, muscle control, and physical conditioning, and are commonly associated with meniscal injuries due to increased instability in the knee. Common causes include:
Sudden direction changes or pivots while running or jumping
Improper landing technique during sports or workouts
Direct impact to the knee from falls or collisions
Weakness or imbalance in thigh and hip muscles
Repetitive strain from overtraining or limited recovery time
Women are slightly more prone to ACL injuries due to differences in joint anatomy and hormone-related ligament flexibility. Being aware of these factors helps in designing smarter, safer exercise habits.
How is an ACL injury detected?
While MRI and physical tests confirm ligament damage, blood biomarkers can reveal inflammation and muscle recovery patterns that support early intervention and rehabilitation planning.
Key markers linked to ACL and ligament health include:
CRP (C-reactive protein): indicates inflammation after injury.
CK (creatine kinase): measures muscle strain or recovery.
Vitamin D and calcium: reflect bone and connective tissue strength.
Cortisol: chronic elevation may slow ligament healing.
Collagen turnover markers: provide insight into tissue repair.
Why early detection matters
A partial ACL injury can often heal with rehabilitation and strengthening, but delayed detection increases strain on the knee joint. Early insight allows you to:
Strengthen stabilizing muscles before further stress occurs
Support recovery through optimal nutrition and rest
Monitor inflammation and healing progress through blood tests
Knowing your body’s response early can prevent long-term instability and protect overall joint function.
How Elfcare can help
Elfcare’s preventive health checks measure key biomarkers related to inflammation, tissue recovery, and bone support. These insights can help you track how your body responds to training, injury, and healing.
The goal is not diagnosis; it’s awareness. Understanding what your results mean allows you to discuss them with your doctor or physiotherapist and take informed steps for a faster, more complete recovery.
Summary
ACL injuries don’t just happen to athletes. They can occur in anyone during quick movements or daily strain. Most start with small ligament stress that, when recognized early, can be managed effectively.
By combining awareness, movement mindfulness, and simple biomarker testing, you can maintain knee stability and prevent long-term complications.
When you understand your body, you can make choices that support your movement, confidence, and lifelong strength.
Last updated: 10 Feb. 2026
Reviewed by: Specialist doctors from the quality team at Elfcare
FAQs
What is an ACL injury?
An ACL injury occurs when the anterior cruciate ligament in the knee is overstretched or torn. This ligament plays a crucial role in stabilising the knee during movements such as turning, jumping, or sudden stops. When it is injured, the knee may feel unstable and less reliable during everyday activities.
What are the most common symptoms of an ACL injury?
Common symptoms include a sudden “pop” in the knee, followed by pain, swelling, and a feeling that the knee may give way. Some people also experience difficulty fully bending or straightening the knee. Even if pain decreases after a few days, underlying instability may still be present.
What causes an ACL injury?
ACL injuries are often caused by sudden changes in direction, awkward landings, or direct impact to the knee. Muscle imbalances, poor movement technique, overtraining, or inadequate recovery can increase the risk. Anatomical and hormonal factors also make some individuals more susceptible.
Can an ACL injury be treated or prevented?
Yes. Many ACL injuries can be managed with early rehabilitation, muscle strengthening, and movement training, while some cases may require surgical intervention. Although not all injuries can be prevented, improving strength, balance, technique, and recovery can significantly reduce risk and support long-term knee stability.