Osteochondrosis dissecans (OD) is a disease that frequently occurs during growth and young adulthood and affects the knee joint in approximately 85% of cases. In the course of this disease, bone death occurs close to the cartilage, whereby a piece of cartilage located above the affected bone region can detach from its bond.
The knee joint is formed by the thigh and lower leg bones and the kneecap. Osteochondrosis dissecans mainly affects the thigh bone (femur condyles) that forms the joint. Mostly the lateral part of the inner (medial) femoral condyle is affected, but also the outer femoral condyle or the rear surface of the patella can be affected.
Causes of Osteochondrosis dissecans
The cause for the development of osteochondrosis dissecans is mostly unknown (idiopathic). One of the existing and most widely accepted theories sees recurrent impulse stress of the knee joint as the cause of the development of osteochondrosis dissecans. According to this theory, it is a mechanical damage to the knee joint, as can occur in sports during recurring stopping or impact movements. Other theories describe a nutritional or circulatory disorder of the knee joint bone, incorrect loading, ossification disorders, and genetic influences. However, no theory can really explain osteochondrosis dissecans.
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Symptoms of Osteochondrosis dissecans
There is no history of osteochondrosis dissecans (anamnesis) that points the way forward. More often, it concerns teenagers and young adults engaged in sports who suffer from the symptoms.
In the early phase of osteochondrosis dissecans, there are no characteristic symptoms and complaints. Initially, the increasing bone mortality is not noticed. Random findings on x-rays of the knee joint are possible.
Later, patients with osteochondrosis dissecans may suffer from stress-related pain in the knee joint. This pain is uncharacteristic and challenging for the patient to describe. Degradation products of the cartilage can lead to inflammation of the mucous membrane (synovitis) and joint effusions. Once a joint mouse has finally formed, symptoms such as entrapment and blocking of the knee joint movement (inhibition of extension and flexion) may occur. The mouse can damage the healthy cartilage of the knee joint. Osteochondrosis dissecans disease is classified as pre-arthrosis, i.e., as a result of this disease, knee joint arthrosis (gonarthrosis) can develop more rapidly than usual with increasing age.
In about 25% of cases, the disease can be bilateral. This does not have to correlate precisely in time.
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For a mostly unknown cause, a gradual bone death occurs in a circumscribed bony area of the knee joint that carries cartilage. In most cases, the circumscribed area is no larger than a cherry or plum stone.
In very early phases of the disease, only very discrete bone changes are detectable. Later, there is a sharp demarcation (demarcation) of the dying bone tissue from the healthy bone tissue, which can be recognized by a bone compaction (sclerosis border). The blood supply is now completely cut off.
Due to the bone dying, the associated cartilage region increasingly loses the bond to its bony underground. If osteochondrosis dissecans progresses further, a piece of cartilage or a piece of cartilage/bone is wholly loosened from the remaining cartilage compound. The dissecant can no longer hold a connection that is initially still connective tissue, which leads to the formation of a free joint body. In this case, one also likes to speak of a joint mouse. The associated dead bone area is called the mouse bed.
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Stages of Osteochondrosis dissecans
Osteochondrosis dissecans is divided into different stages.
These stages are mainly used for diagnostic purposes and are proven by X-ray examinations. For example, if a patient expresses stress-related pain, the X-ray examination can determine whether osteochondrosis dissecans is in its early stages or whether the disease is already more advanced.
A total of three different stages of the disease are distinguished, which are typically passed through one after the other. However, it is possible that a patient may find the first stage to be less severe and, therefore, only consult a doctor in the second stage of Osteochondrosis dissecans. In this case, the disease is diagnosed in stage 2, which does not mean that the first stage has not been completed.
However, stage 1 is known as the so-called slumber stage, as it goes unnoticed by many patients. In this slumbering stage, the disease gradually begins, and an inflammatory process develops in the bone due to poor blood circulation. In this process, the bone cells are attacked. This first stage of osteochondrosis dissecans is described in medicine as osseous demarcation (demarcation between destroyed inflamed bone and healthy bone).
This stage can also be divided into two stages. In this case, stage 1 is considered to be the beginning of the inflammatory process, whereby the bone still appears normal on X-ray, and stage 2 of osteochondrosis dissecans is then the stage of visible osseous demarcation. Assuming a total of 3 stages, the slumbering stage is now followed by stage 2 of Osteochondrosis dissecans. In this stage 2, the x-ray clearly shows that the broken bone separates from the healthy bone and is no longer supplied with blood and is therefore no longer viable.
The cartilage layer may also be affected and may either be slightly swollen (oedematous) or also have damaged parts.
In stage 3 of osteochondrosis dissecans, a hole is then seen in the area where the dead piece of bone was located, the piece of bone itself remains as dead bone fragments.
Authors who assume four stages in osteochondrosis dissecans refer to this last stage as stage 4, and the above-mentioned stage 2 is then regarded as stage 3.
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At the ankle joint
Osteochondrosis dissecans at the ankle joint is a rare disease, only in about 5 percent of all cases the ankle joint is affected, more often the disease occurs at the knee or elbow. Repeated ankle injuries probably cause osteochondrosis dissecans at the ankle joint, i.e., it is triggered by traumatic cartilage and bone damage. Severe sports activities in children or adolescents seem to increase the risk of osteochondrosis dissecans.
In children with osteochondrosis dissecans, immobilization of the ankle for as little as six weeks usually supports natural healing. In adults, it is often unavoidable to perform a surgical refixation or bone transplantation as part of an ankle arthroscopy.
The disease is often first noticed by pain in the depth of the upper ankle joint. The pain typically increases under stress and subsides at rest. Only rarely does osteochondrosis dissecans manifest itself through clearly defined pain or blockages. Sometimes there are no symptoms, and the disease is discovered by chance. The disease increases the risk of developing ankle degeneration (arthrosis), as it causes damage to bone and cartilage. To avoid this, the treatment of osteochondrosis dissecans of the ankle joint should start as early as possible.
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At the talus
Osteochondrosis dissecans of the ankle joint usually affects specific areas of the talus (ankle bone). The talus is a short bone and a component of the ankle and tarsal. It connects the foot to the leg and is located between the ankle fork (malleolus fork) and the heel bone (calcaneus). On the upper side of the talus, there is the trochlea tali (ankle bone roll), which is curved in the middle and has raised lateral edges. Osteochondrosis dissecans affects these upper edges of the talus, with the inner edge being more frequently affected than the outer edge. Since the inner edge is the central weight-bearing part of the joint surface, this indicates that osteochondrosis dissecans at the ankle joint is load-dependent.
Osteochondrosis dissecans at the knee
The knee is the most common site for osteochondrosis dissecans.
The most common site of osteochondrosis dissecans is the knee (about 75 percent of all cases). The weight-bearing parts of the joint surfaces are usually affected, i.e., the lateral (lateral) and medial (internal) condyles of the thigh.
The bone is primarily affected by the disease, as the cartilage is supplied with nutrient-rich synovial fluid from the joint. The cause of the death of a bone close to the joint below the cartilage is probably a temporary circulatory disorder. Disease is often associated with a disturbance in the movement of running and jumping. This results in a short-term rotation in the knee with the subsequent impact of the bones involved in the joint. However, pathological meniscus changes (e.g., a disc meniscus) and childhood rheumatism are also discussed to osteochondrosis dissecans of the knee.
The disease mainly affects children, adolescents, and young adults; also, about twice as many men as women are affected. In about 70 percent of cases, only one knee joint is affected by osteochondrosis dissecans. Symptoms can be very different, often the pain occurs when the affected knee joint is strained, but also joint swelling due to the formation of a joint effusion and movement restrictions of the knee joint are described.
In cases of low severity or young, still growing people, the disease can be treated by physical rest and physiotherapeutic care. Knee arthroscopy is only necessary if there is no cure or if the disease worsens.
The best and safest method of diagnosis is to perform an MRI of the knee.
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At the elbow
Osteochondrosis dissecans of the elbow is probably caused by a circulatory disorder of a part of the elbow bone. Another hypothesis is that osteochondrosis dissecans of the elbow is caused by an overload reaction of the bone as a result of extreme and frequent arm movements (e.g., during throwing movements during sports).
In most cases, osteochondrosis dissecans affects the outer humeral roll (capitulum humeri). However, it can also occur at the spoke head (caput radii) or the inner humeral roll (trochlea humeri). In osteochondrosis dissecans of the elbow, varying degrees of pain is felt in the affected elbow and cracking or rubbing, blockages or entanglements may also occur.
The diagnosis is usually made using an x-ray of the elbow joint. More sensitive is the imaging of the elbow using magnetic resonance imaging (MRI), since it can also show earlier stages of osteochondrosis dissecans.
The course of the disease can vary greatly. In some cases, the osteochondrosis dissecans of the elbow are unproblematic and without consequences, and the disease can also leave severe permanent traces. Osteochondrosis of the elbow has a favorable prognosis, the younger the person affected is, if the growth plate of the outer upper arm roll is still open and the smaller the spatial extent of osteochondrosis dissecans.
Therapy consists of a break from sports, the administration of anti-inflammatory drugs, and, if necessary, a plaster cast for a few days. Surgery may become necessary if the osteochondrosis dissecans at the elbow deteriorates, the affected bone area threatens to detach, or a free joint body (piece of bone that “floats” freely in the joint) has developed.
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An MRI examination is the most reliable way to diagnose osteochondrosis dissecans and helps to classify the stages. An X-ray often shows the typical changes long after the actual circulatory disturbance, which is why the diagnosis is often made late. Before MRI examinations were possible, osteochondrosis dissecans was only discovered when the affected piece of cartilage-bone was detached, as this caused blockages.
Magnetic resonance imaging (MRI) allows the exact location and size of the osteochondrosis dissecans, the depth extension, and, above all, the involvement of the overlying cartilage to be measured. This also allows statements to be made about the stability of the affected joint. MRI is also very suitable for monitoring the course of the disease, but simple X-ray examinations can also be carried out if necessary.
An MRI should always be performed on both sides since osteochondrosis dissecans occurs on both sides in about 40 percent of cases.
Osteochondrosis dissecans in detachment during knee arthroscopy
The diagnosis of osteochondrosis dissecans includes a detailed anamnesis (medical history).
The physical examination excludes other possible diseases (differential diagnosis) as far as possible. There is no specific examination technique with which osteochondrosis dissecans can be reliably diagnosed. Recurring blockage symptoms in advanced osteochondrosis dissecans caused by a trapped joint mouse are indicative. However, the same phenomenon is also found in certain forms of meniscus injury and in free joint bodies of other causes (e.g., chondromatosis).
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Diagnosis by imaging techniques
Sonography (ultrasound) is a readily available and suitable method for detecting knee joint effusion. Depending on the position of a free joint body, this can also be detected.
X-rays can detect advanced osteochondrosis dissecans. Standard a.p. radiographs are usually sufficient. (from the front) and lateral. The tunnel image, according to Frik is also helpful. The typical changes are most frequently found in the lateral part of the inner femoral condyle. The X-ray does not provide evidence of the early stages with beginning bone death. The first signs are an oval bone brightening (dark spot) at the described site, which is later limited by a whitish rim (sclerosis zone). The resulting dissociate can eventually detach itself from its composite as a whole or in several small parts. This can be recognized by the evidence of free joint bodies and a hollow in the knee joint bone.
With the MRI (magnetic resonance imaging) of the respective region (e.g., MRI of the knee, MRI of the ankle or MRI of the elbow, etc.), an early diagnosis of osteochondrosis dissecans is possible. It is also important to exclude almost all other possible diseases from the diagnosis. The stage of bone death can be determined by MRI, as well as the nutritional situation of the dissecate.
The nutritional situation of the dissected bone can also be used to determine the extent to which rejection of the dissected bone is to be feared. However, an exact time cannot be determined by the MRI. Discs that have already been rejected can be reliably detected by MRI.
The most precise examination, however, is possible with a knee joint endoscopy (arthroscopy) if the knee joint is affected. If another joint is present, it can be arthroscopied in the appropriate manner (e.g., ankle joint)
It has the advantage that the stability of the OD region can be reliably checked with a tactile hook (see illustration: Loose OD region, very enlarged), and it can be seen whether the cartilaginous surface structure is still intact or whether it is already damaged. In the same session, suitable operative therapy measures can then be carried out.
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The usual surgical complication possibilities apply:
- Infection, bone infection, wound healing disorder.
- Nerve injuries
- Pulmonary embolism
- Recurrence/failure of the operation = new joint mouse renewed loosening of the cartilage bone fragment
- Early Arthrosis
Osteochondrosis dissecans is a severe disease of the knee joint. If left untreated, osteochondrosis dissecans is considered to be pre-arthrosis, i.e., those factors that lead to the development of early knee joint arthrosis (gonarthrosis). Through the above-mentioned surgical measures, the damage to the knee joint can be reduced to a minimum, and the ability to engage in sports can be regained for the mostly young patients.
Especially in very young patients, the spontaneous course of the disease can be awaited. Spontaneous healing is described in up to 50% of cases.
The prognosis is best if the dissection can be prevented by revitalizing the bone area. All other procedures with refixation of the dissectate or insertion of a replacement tissue have a worse prognosis since the knee joint reacts very sensitively to even the smallest irregularities of the cartilaginous surface structure in the long term.
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