A tear of a cruciate ligament will represent a major injury to any patient. This multi-page Primer highlights the key issues.
- The cruciate ligaments
Cruciate ligament tears
- The torn anterior cruciate ligament (ACL)
- The torn posterior cruciate ligament (PCL)
- Multiligament instability of the knee
- Cruciate ligament repair
- Cruciate ligament reconstruction
- Cruciate ligament rehabilitation
- Complications of cruciate reconstruction
Page updated July 2023 by Dr Sheila Strover (Clinical Editor)
The ACL may also be injured when cutting to the same side as in this image.
Less frequently, the ACL is injured in a contact injury, one where the knee is forcibly hyper-extended, and the other where the knee is forcibly hyper-flexed.
Both cruciates are necessary for full stability of the knee. If the tibia is forced forwards the ACL takes the strain. If the tibia is forced backwards the PCL takes the strain.
Early indicators of a cruciate tear
A tear of the cruciate ligament can be suspected if most of these features are present:
a definable injury or event
Patients with a torn cruciate generally recall the moment that the cruciate ligament gave out. Although the injury may be a contact or a non-contact injury, it usually involves a twisting of the femur bone and tibia bone in relation to one another.
a loud 'pop' at the time of injury
As the cruciate snaps apart during the injury, very often the patient hears a loud 'pop' which may even be audible to others nearby.
unable to continue with activity
If it is the anterior cruciate ligament that is torn, usually the patient is unable to go on with the activity. Sometimes it is possible to continue if only the PCL is torn.
immediate knee swelling
Because the cruciate ligament has blood vessels in it, usually the knee swells up rapidly with blood (a haemarthrosis). This may become tense and painful and may need aspiration (sucking out with a syringe and needle).
Ongoing symptoms of a torn cruciate ligament
Once the early pain and swelling have subsided, after a week or so after a cruciate injury, then it becomes more easy to evaluate the situation. There may simply be a feeling that the knee cannot be trusted. This may be especially so during twisting activities. Frank instability may be indicative that more than one cruciate is damaged, or that another structure is damaged in addition to a cruciate ligament. Although walking in a straight line may be quite easy, a torn cruciate may allow the knee to suddenly give way and collapse during a twisting motion.
Symptoms of damage to other structures after a cruciate tear
One of the problems of evaluating a cruciate tear is that other stabilising structures may also be torn in the original injury, or the laxity due to the cruciate tear may secondarily lead to damage of other stabilising structures.
damage to the meniscus
damage to the joint surface
Damage to the joint surface may add the symptoms of achy knees and noises in the knee.
damage to the posterolateral corner
Damage to the structures of the posterolateral corner may add the feeling of the knee thrusting outwards with walking, and there may be other disturbances of gait.
What should you do if you think your cruciate is torn?
A cruciate ligament tear is not a medical emergency. Although the injury is a serious one, the early management is relatively uncomplicated:
If pain and swelling are not too bad
If the skin is not damaged in the injury, and pain and swelling are not too severe, most clinicians will recommend the RICE (or PRICE) regime for the first few days of almost any knee injury, ie Protection, Rest, Icing, Compression, Elevation.
If pain and swelling are severe
If the pain and swelling are severe, then it is possible that there is tense blood within the knee cavity (haemarthrosis) and a visit to the Accident & Emergency unit is recommended. The doctor there may chose to aspirate the blood (suck it out with a syringe and needle), a procedure that can give considerable relief. The joint should be held still in an immobiliser brace until the specialist is seen.
When the knee is painful and swollen it is difficult for any doctor to fully examine and evaluate the knee. Once the injury has settled down, maybe after a week or so, then it is much easier to examine. Most surgeons will not operate anyway when the knee is still inflamed.
Why do women get more cruciate tears than men?
As women increasingly enter competitive and demanding sports, surgeons are seeing more and more women with cruciate injuries. Researchers are identifying a number of reasons for the high incidence of cruciate injury in this population group, and found that women:
have a narrower notch in the femur
It is speculated that the narrower intercondylar notch (the notch between the two rounded ends of the femur bone) in women may contribute to cruciate damage.
have a relationship between cruciate injury and their ovulation cycle
Research has demonstrated that women who injure their cruciate ligament are more likely to do so mid-cycle.
have relatively weak hamstrings compared to men
The strength of the quadriceps is stronger compared to the hamstrings muscle in women, while men have more balanced muscles.
have a less flexible stance and stiffer landing during sporting activities
Women tend to keep their trunks more upright than men during sporting activities, and tend to use the squatting position less. Women tend to absorb the impact of landing poorly in comparison to men.
With specific training the incidence of cruciate damage in women approaches that in men.
The problems of cruciate tears in children
Cruciate ligament tears in children used to be very uncommon, but they are becoming more common as children participate more in demanding sports.
The issue of such injuries in children is that their bones are still growing, with special regions towards the ends of long bones ('growth plates' or 'open physes') having very actively-dividing cells. When a child becomes an adult, the cells in the physes stop dividing and are said to 'close'.
Surgeons are likely to be reluctant to do a cruciate ligament reconstruction on a child before the physes close, leaving the child vulnerable to ongoing knee instability and secondary damage to the meniscus or the joint cartilage surfaces. The reason for the reluctance is that any tunnels drilled through the bone to accommodate the graft are likely to go through the physis, and this may arrest growth or cause bany deformity. So the decision of whether to operate or not is a difficult one, and different surgeons will have different opinions on this. It is best to consult a surgeon who has a special interest in working with children.
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