Understanding a major consequence of anterior cruciate ligament injuries
Knee instability is one of the most frequent and debilitating consequences of an anterior cruciate ligament injury, commonly called LCAOften described by patients as a feeling of the knee "giving way", "giving way" or lacking reliability, this instability can profoundly alter quality of life, limit sports practice and expose the joint to secondary injuries.
Understanding why and how this instability occurs, knowing how to recognize it and being aware of the available therapeutic solutions is essential to prevent long-term complications and preserve knee function.
The central role of the ACL in knee stability
The anterior cruciate ligament (ACL) is a key element in the structure of the knee. Located in the center of the joint, it performs a dual mechanical and sensory function. Mechanically, it prevents the tibia from sliding forward relative to the femur and limits excessive rotation. Sensorily, it contributes to proprioception, that is, the body's ability to perceive the position and movement of the knee in space.
When the ACL is intact, it acts as a dynamic stabilizer, allowing for precise, fluid, and secure movements. Conversely, when it is torn or severely stretched, this balance is disrupted. The knee then becomes dependent on muscles and other ligamentous structures to maintain its stability, which is not always sufficient.
How does knee instability manifest itself?
Knee instability is not only characterized by pain. It is primarily felt as a lack of control over the joint. Patients often describe apprehension about performing certain movements, for fear that the knee will give way.
The most frequent manifestations include:
- a sensation of "giving way" when applying pressure,
- repeated episodes where the knee seems to lose its stability,
- a loss of confidence in articulation,
- sometimes secondary pain, linked to repeated microtrauma.
These episodes of instability can be occasional or frequent. When they recur, they significantly increase the risk of associated injuries, particularly to the menisci and cartilage.
Acute instability and chronic instability: two different situations
It is important to distinguish between two forms of instability related to the ACL.
Acute instability appears shortly after ligament rupture. It is often associated with knee swelling, residual pain, and difficulty resuming normal activities. This phase corresponds to a period of joint adaptation.
Chronic instability, on the other hand, develops over the long term when the ligament has not been repaired or when muscle compensation is insufficient. The knee then becomes repeatedly unstable, sometimes several months or years after the initial injury. This chronic instability is particularly detrimental to the joint.
The consequences of untreated instability
Persistent knee instability is not only uncomfortable; it is potentially destructive. With each episode of buckling, the internal structures of the knee are subjected to abnormal stresses.
In the medium and long term, this can lead to:
- repeated meniscal tears,
- premature wear of the articular cartilage,
- chronic inflammation
- the development of osteoarthritis of the knee, sometimes early.
These complications explain why ACL instability should never be trivialized, even when the pain seems moderate.
How to evaluate it?
The assessment of instability relies on a detailed interview and a specialized clinical examination. The healthcare professional seeks to understand the situations in which the knee becomes unstable and how frequently these episodes occur.
The clinical examination includes specific tests to identify excessive tibial displacement or rotational instability. These tests are sometimes supplemented by imaging studies.
MRI is particularly useful because it allows:
- to confirm the ACL injury,
- to assess the condition of the menisci,
- to analyze the condition of the cartilage,
- to guide the therapeutic decision.
Is it possible to live with knee instability related to an ACL injury?
The answer depends heavily on the patient's profile. Some people manage to compensate for the absence of the ACL through significant muscle strengthening and good proprioception. They can lead a relatively normal daily life, provided they avoid certain risky movements.
However, in active or athletic patients, this compensation is often insufficient. The knee remains vulnerable, and each episode of instability increases the risk of secondary injuries. This is why appropriate management is essential.
What are the treatment solutions?
Functional treatment
Non-surgical treatment aims to improve knee stability through indirect means. It is primarily based on:
- strengthening of the stabilizing muscles, particularly the quadriceps and hamstrings,
- proprioceptive work,
- the adaptation of physical activities.
This approach may be sufficient for patients who are not very athletic or who only have moderate instability.
Surgical treatment
When instability persists despite well-conducted rehabilitation, surgery becomes the preferred option. Anterior cruciate ligament reconstruction restores the mechanical stability of the knee and significantly reduces episodes of buckling.
The intervention is followed by a long and structured rehabilitation, essential to regain a stable and functional knee.
Rehabilitation: a key element in controlling instability
Whether performed alone or after surgery, rehabilitation plays a central role in managing instability. It aims not only to strengthen the muscles, but also to retrain the neuromuscular control of the knee.
A well-conducted rehabilitation program allows for:
- to reduce the feeling of instability,
- to restore confidence in the knee,
- to ensure the safe resumption of physical activities.
Conclusion
Knee instability related to the anterior cruciate ligament (ACL) is a common and serious consequence of an ACL rupture. It should never be considered mere discomfort, as it exposes the joint to progressive damage. With accurate assessment, appropriate rehabilitation, and, if necessary, surgical intervention, it is now possible to restore satisfactory stability and preserve knee function in the long term.
