Traumatic osteoarthritis after a knee injury 

Anterior cruciate ligament injury and post traumatic osteoarthritis

The anterior cruciate ligament plays a major role when it comes to stability of the knee. In particular, it inhibits the translation (shift) forward and unwanted rotation of the knee joint. The incidence of an anterior cruciate ligament injury is about 69 per 100,000 people. 

"These figures are often used in medical contexts to describe the number of new cases of a particular disease or condition. In this case, incidence represents the number of people, about 69 per 100,000 people per year, who suffer an injury to the anterior cruciate ligament. These figures help health professionals and researchers better understand how common a particular condition is and how it progresses over the total population or over specific groups within that population." 

The main characteristics of an anterior cruciate ligament injury are: pain, instability, decreased mobility, decreased strength especially in the quadriceps, altered biomechanics and reduced ability to perform a variety of daily activities. An anterior cruciate ligament injury often occurs as a result of having to quickly slow down and change direction during explosive movement. In 75% of all cases, it is a non-contact injury. Thus, there is no collision or injury here at the hands of another person. Another striking point is that young women are up to 5 times more likely to develop an anterior cruciate ligament injury compared to men. One possible reason for this are hormonal changes in this age group along with the anatomical position of the pelvis relative to the knee and ankle joint. We call this the Q angle. In women, there is often a larger Q-angle compared to men. The enlarged Q-angle causes a different biomechanical load on the knee joint in women. Here the main issue is an enlarged valgus position of the knee(X-legs). This means that the knee is more inward and can negatively contribute to knee stability during sports. 

A grade 3 or 4 on the kellgren-lawrence score is 5x more common in the knee that experienced an anterior cruciate ligament injury compared to the other side. 

Factors that increase the risk of post traumatic osteoarthritis after anterior cruciate ligament injury 

• Older age
• Women are more likely than men 
• High BMI(body mass index) 
• Overweight 
• Smoking 
• Consecutive surgeries in the same joint 
• The time between the onset of injury and surgery 
• Varus position(x-legs) 

Age
When people tear their anterior cruciate ligament at a later age, we observe a narrowing of the joint gap earlier than in younger people. The reason for this is that at older ages there is a disruption in the repair ability of the cartilage compared to younger people. As we age, the cartilage in our joints undergoes changes as a result of a complex interplay between building and breaking down processes. These processes play a crucial role in maintaining healthy cartilage. The ability of cartilage to repair decreases with age. For this reason, we see that later in life, the quality of cartilage due to injury will decline more rapidly. 

Overweight
In people with an increased BMI, we see that osteoarthritis symptoms are more likely to occur, and more specifically, narrowing of the joint gap after an anterior cruciate ligament injury. Being overweight in itself has a major impact on getting osteoarthritis. One of the reasons especially in the knee joint is greater stress on the joint. Another important reason is that fat cells produce inflammatory mediators that can reach various joints in this way. 

Adipokines
In overweight or obese people, fat cells can produce hormones known as adipokines. These adipokines play a role in various inflammatory processes. This inflammatory response is associated with an increased risk of various health problems such as metabolic disorders(diabetes), cardiovascular disorders(cardiovascular disease), as well as joint problems such as osteoarthritis. We also see that inflammatory processes caused by adipokines can also slow down the healing process after injuries. 

Ignition mediators
Inflammatory mediators are molecules involved in inflammatory responses. In particular, these are cytokines. These are proteins whose function is to activate the immune system when there is an inflammatory response. Thus, they act primarily as messengers between different cells and molecules. An inflammatory response is a normal reaction of the body to injury, injury or stress. 

With osteoarthritis symptoms or after an anterior cruciate ligament injury, an inflammatory reaction often occurs as part of the healing process. However, a prolonged inflammatory reaction can also interfere with the healing process and perhaps worsen tissue damage. For this reason, it is important to properly manage and control the inflammatory response. At Physio Fitaal, we are very critical of the first phase after anterior cruciate ligament surgery(0-6 weeks). It is important to properly manage this inflammatory process in the first phase of rehabilitation to get a good start and promote optimal healing. 

In a nutshell, both fat cells and inflammatory mediators affect the body's ability to recover and play a role in both the onset and recovery of injuries, including anterior cruciate ligament rehabilitation. Properly understanding and monitoring these complex processes gives you a head start in the early stages of recovery and can have major implications for the rest of rehabilitation. 

Post-traumatic osteoarthritis after anterior cruciate ligament injury

The reason for the onset of post-traumatic osteoarthritis after an anterior cruciate ligament injury can be looked for in several angles: 

1. Structural factors 
2. Biological factors 
3. Mechanical factors
4. Neuromuscular factors

Structural factors
Along with rupture of the anterior cruciate ligament, we often see other damage occurring during the injury moment. When there is no other damage we speak of isolated injury of the anterior cruciate ligament. When there are multiple structures that are damaged, for example, the meniscus, capsule of the knee or the subchondral bone, we see that post-traumatic osteoarthritis occurs more quickly over time. The more forces are released during the injury moment the greater the chance of further damage in the joint. Especially with damage in the meniscus, which has primarily a protective function in the joint, we see early development of osteoarthritis. 

An anterior cruciate ligament surgery and post-traumatic osteoarthritis

Most people who tear their anterior cruciate ligament and want to return to a similar level of sports often choose to have the anterior cruciate ligament surgically repaired. We call this an anterior cruciate ligament reconstruction. Among other things, the function of the anterior cruciate ligament is to inhibit forward (ventral) shear forces. Among other things, repairing the anterior cruciate ligament provides more inhibition of forward translation and inhibition of excessive rotation in the knee. 

Artrokinematics

Repairing the anterior cruciate ligament can be done in several ways: 

Hamstring graft: In this option, the tendons of the hamstring, usually the semitendinosus and gracilis are used to form the new anterior cruciate ligament.

Quadricepsgraft: The central part of the quadriceps is used as graft material. 

Bone-patella-bonegraft:  As the name implies, this graft uses the patellar tendon and two pieces of bone. These pieces of bone come from the tibia and patella. 

We see that different reconstructions, repairing the anterior cruciate ligament through surgery, affect the arthrokinematics of the knee joint. Arthrokinematics is another word for movement pattern. This change in movement pattern due to reconstruction can cause other parts of the knee to be stressed during movement. Gait analyses show that there is almost always a different movement pattern in the knee and especially in rotational movements relative to the non-surgical leg or compared to non-surgical subjects. 

KCOR - knee center of rotation 

This easily translates to rotation center of the knee in Dutch. This is the point where the rotational movement in the knee occurs when the knee is flexed and extended. The center of rotation is important to properly understand the movements in the knee. Knowledge of this center of rotation is also important when designing knee replacements, for example, and when planning other surgical procedures such as anterior cruciate ligament reconstruction. The position of the KCOR can vary and depends on individual anatomy. A good understanding of the point of rotation helps medical professionals optimize the treatment plan and other interventions to treat knee-related complaints. 

Early detection of post-traumatic osteoarthritis 

Post-traumatic osteoarthritis is a process that will worsen to a greater or lesser degree over time. For this reason, it is important to detect this form of osteoarthritis early. Imaging studies such as X-ray, MRI, CT scans play a major role in this. But also research into various biomarkers in the blood, as explained earlier the cytokines can contribute to early recognition of the onset of osteoarthritis symptoms. 

Taking an X-ray is by far the most common form of imaging examination to make a statement about the quality of cartilage in the knee.But we also see that X-rays are often unable to detect early osteoarthritis. Also, when classifying the degree of osteoarthritis, there is often disagreement between the assessors of the photo, such as doctors or radiologists. Analyzing a photograph is human work and remains subjective. An X-ray also provides no information about, for example, the quality of the meniscus, the condition of the synovium (joint fluid), other ligaments of the knee or the inner part of the cartilage. 

Unlike an X-ray, an MRI is more of a three-dimensional picture of the knee. It can analyze multiple structures and provides much more information about the condition of different aspects in the knee. Some examples include: subchondral damage, bone edema and minimal changes in the cartilage surface. DIt therefore gives more of an overall picture of the knee. Compared to X-rays, an MRI is more expensive and not available everywhere. 

Many different processes play a role in the development of post-traumatic osteoarthritis. Being able to observe certain markers in the blood, for example, could provide valuable information about the actuality of various inflammatory processes in the body. In theory, it could detect osteoarthritis earlier than osteoarthritis can be seen on a photograph.

*Imaging tests are always requested by a physician. Please also leave this to the expertise of your treating physician. The intent of this article is not to encourage additional imaging studies. Leave this to the medical specialists. 

Can we prevent post-traumatic osteoarthritis? 

The most effective form to combat post-traumatic osteoarthritis is to prevent it. Preventing anterior cruciate ligament injuries plays a major role in this. Research shows that programs aimed at improving neuromuscular control, muscle strength training, stability training and educating about risk factors can reduce anterior cruciate ligament injuries. There are several prevention programs for specific sports where Fifa11+ is the best known. Other research shows that in a research group consisting of college-level male soccer players the use of the Fifa11+ program there was approximately a 70% decrease on the number of anterior cruciate ligament injuries. 

There are several explanations for why post-traumatic osteoarthritis develops after an anterior cruciate ligament injury. The more forces are released during the genesis of the anterior cruciate ligament injury, the greater the likelihood of other damage in the joint. This usually involves damage to the meniscus, capsule of the knee or damage to the cartilage itself. Because cartilage is poor at repairing, damage to the cartilage can directly result in osteoarthritis in the knee. 

Another reason is an altered movement pattern in the knee after tearing the anterior cruciate ligament in the knee. After a significant anterior cruciate ligament injury, it is often the case that there is less stability in the knee. As a result, the mechanical load is different in the knee joint. Other parts of the cartilage are stressed much more than normal in this way. After an anterior cruciate ligament injury, we also often see a significant decrease in muscle strength especially in the quadriceps and to a lesser extent the hamstrings. This decrease in strength also causes decreased stability and can contribute to a different walking pattern. Because of the pain and fear of further injury or provocation of symptoms, we see that it is precisely the muscular strength and control of the knee that causes more symptoms. 

In a non-injured weight bearing, the forces that come on the knee in this case are evenly distributed over the cartilage surface during activities such as walking, running and jumping. With an altered movement pattern, on the contrary, we see an uneven distribution of the load on the cartilage and parts become overloaded faster and in the long run can lead to osteoarthritis in the knee. Precisely the balance between load and relief, pressure and no pressure in the joint will ensure healthy cartilage. Is there too much pressure on certain parts of the cartilage will lead to a reduced quality of that cartilage. The loss of stability normally provided by the anterior cruciate ligament is absorbed by other structures in the knee. So these will have to endure more which may lead to strain in the joint and eventually the cartilage. 

Impaired control of the knee can also contribute to osteoarthritis in the knee. The anterior cruciate ligament not only provides passive stability in the joint, but also contains sensors that help provide information to the brain. The loss of this causes less neuromuscular control. This leads to a decrease in strength of muscles around the knee. This decreased strength, in turn, indirectly plays a role on the pressure load on the joint. Which, as explained earlier, plays a role in the faster development of osteoarthritis-related symptoms in the knee.

Conclusion

To minimize the long-term effects of post-traumatic osteoarthritis and prevent early symptoms of osteoarthritis, this form of joint damage must be identified quickly. Unlike osteoarthritis due to aging, post-traumatic osteoarthritis has a clear starting point. Treating quickly after injury plays an important role in preventing future symptoms. This applies to both rehabilitation after surgery or when choosing not to repair the anterior cruciate ligament. A thorough rehabilitation program will help improve neuromuscular control, muscle strength and active stability of the joint leading to improved function of the knee joint. 

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