Koenig’s disease or osteochondrosis (osteochondritis) dissecans is a disease in which cartilage that covers bones gradually exfoliates and can even completely separate from the bone. If the cartilage area is separated from the bone, then it will move freely along the knee joint, interfering with movements.
The disease most often occurs in young people (18 to 35 years old), especially in athletes involved in active sports. Localization of the process is more often observed in the area of the inner condyle of femur, that is, only in those areas that are subject to the greatest functional load. Long-term overload and repeated micro injury of the femoral condyles lead to relative insufficiency of blood supply, violation of bone structure with further formation of focus of aseptic necrosis (destruction of the bone and cartilage). In the future, separation is possible of the site of articular cartilage with subchondral bone – the formation of a free bone-cartilaginous body and a defect in the articular surface.
Bone-cartilage defect of the knee joint in Koenig’s disease
The disease has staging, or gradually progresses, and if the course of the disease is not interrupted by surgery, another treatment option or if spontaneous, sudden and unreasonable recovery happens, the area of necrotic subchondral layer and the cartilage covering it will separate and a free intra-articular body will appear, and in the place of the detached fragment, a section of “bare” bone is formed.
Four stages of the disease are distinguished. At the first, initial stage of the disease, the cartilage at the site of lesion becomes softer, but it does not have clear boundaries. The second stage is characterized by the appearance of distinct boundaries of cartilage damage, but cartilage remains motionless. In the third stage, cartilage fragment is already shifted by several millimeters relative to the underlying bone but remains attached to it, and in the fourth stage of the disease, cartilage and subchondral bone fragment are completely exfoliated and begin to move freely in the joint cavity.
Stages of Koenig’s Disease
Koenig’s disease begins with slight discomfort, aching pain and swelling in the knee joint, aggravated by physical exertion. If the disease proceeds for a long time, lameness leads to decreased amplitude of movements in the knee joint and atrophy of the quadriceps femoris muscle (the thigh becomes thinner).To diagnose the disease at this stage, a careful analysis of anamnestic, clinical, radiological and MRI data is necessary, since there are no pathognomonic (specific) symptoms. At the first stage of Koenig’s disease, no significant signs are found on X-rays. Sometimes you can see the so-called signs of “compression damage.” In the second stage of the disease, bone fragment itself appears, but its borders are not distinguished around the entire circumference – it remains firmly connected with the bone. In the third stage of the disease, X-rays show a bone fragment that has clear boundaries around the entire circumference, but the fragment itself is located in its place, i.e. it is retained by the cartilage layer. And finally, in the fourth stage of the disease, the fragment migrates, and a “hole” remains in its place. To exclude damage to menisci and other soft tissue structures, as well as to better visualization of the lesion, MRI is used. Early diagnosis can help reduce the load in time, conduct intensive conservative treatment and stop the development of the disease in young patients.
The treatment for Koenig’s disease depends on the age of a patient and the stage of the disease. In young patients with unclosed growth zones (usually under 20 years of age), conservative, i.e. non-surgical treatment is preferred. Its principle is to give rest to the joint, which will lead to the regression of the disease.
In case of disease progression and separation of the bone-cartilage fragment, the clinical picture becomes brighter. Periodic blockade of the joint adds to the intensified pain syndrome. Conservative treatment at this stage of the process is futile.
The aim of surgical treatment of Koenig’s disease is to restore the congruency of the articular surfaces and improve the nutrition of subchondral bone in the defect zone, which leads to a decrease in pain and is the prevention of osteoarthritis. The option of surgical treatment is determined by the stage of the disease. Fundamentally, there are two options: to fix the fragment back or to remove it, and to perform chondroplasty in the place from which it was separated, i.e. attempt to restore cartilage. Chondroplasty includes tunneling, mosaic chondroplasty, periosteal grafts.
Mosaic chondroplasty of the condyle of the knee joint in Koenig’s disease
The main complication of Koenig’s disease is arthrosis of the knee joint. The likelihood of developing arthrosis of the knee joint depends on the location of Koenig’s disease, fragment size, success, timeliness and adequateness of treatment. However, arthrosis may develop despite adequate and timely treatment. Depending on the size and location of the damage, arthrosis of the knee joint develops in 5-40% of cases.