A 15-year-old with Chronic, Intermittent Knee Pain
- Define the structural problem in osteochondritis dissecans
- List the common presenting complaints and radiographic findings in osteochondritis dissecans
- Appreciate the need for early diagnosis and treatment in osteochondritis dissecans
A 15-year-old girl presents with a three-year history of intermittent right knee pain. The pain began insidiously, at first occurring only after vigorous dance routines, but more recently occurring even with prolonged walking or standing. She cannot recall any history of knee injury or significant joint swelling. She denies catching, locking, or giving way. There is no history of other joint problems. She has been evaluated for right knee pain on two occasions in the past, but in each case the knee exam was negative and X-rays were not obtained. Her past medical and surgical history is otherwise negative. She is not on any medications.
Physical examination reveals a healthy, athletic appearing 15-year-old female who walks favoring her right leg slightly. Examination of the right knee demonstrates full range of motion and a trace effusion. The ligamentous exam is negative and there is no joint line tenderness. McMurrays testing is negative, but there is slight tenderness over the anterior aspect of the knee just medial to the patellar tendon. The left knee is unremarkable on examination.
Further evaluation is pursued with imaging as shown below.
Figure 1: Radiographs demonstrate closing growth plates and a defect in the weight-bearing portion of the medial femoral condyle. These findings are classic for osteochondritis dissecans (OCD).
Figure 2: An MRI obtained to further evaluate the lesion reveals it to be intact with no loss of cartilage and no gross instability of the fragment.As the patient was near skeletal maturity, arthroscopic retrograde drilling was performed. A 0.062-inch k wire was drilled into the base of the lesion to penetrate the sclerotic rim and to promote vascular ingrowth and bone healing. Approximately ten such penetrations were made. This was done in a way that did NOT cross the growth plate and did NOT damage the joint surface.
Figure 3: This image demonstrates the use of fluoroscopy to confirm that drilling of the sclerotic base of the OCD lesion has been accomplished. Once visualized, the pins are removed. Postoperatively, the patient was placed on crutches for 6 weeks and followed with X-rays at 3 and 6 months to assess healing.
Juvenile osteochondritis dissecans (OCD) of the knee is a condition that causes a segment of articular joint cartilage to lose its bony support. The cartilage is normal in the early stages of OCD, but if spontaneous healing does not occur, the cartilage will crack and ultimately become a flap or even a loose body. This can result in the loss of a significant portion of the weight-bearing surface of the femur and contribute to late arthritis of the knee. The goal is to diagnose the condition as early as possible when treatment is most likely to be successful.
In the early stages of OCD, symptoms are typically mild, non-specific, or even absent. Examination may reveal slight tenderness over the involved condyle and a small effusion. The diagnosis can only be made with radiographs or MRI. For this reason, as in this case, the diagnosis is often delayed. While not every child presenting with knee pain should have X-rays, those with persistent symptoms or symptoms that return even after a few months of activity modification or rest should be evaluated with plain radiographs. Radiographs are also indicated when an effusion is noted on examination or the patient gives a history of catching or locking.
When OCD of the knee is suspected, an AP and lateral radiograph is not sufficient. Lesions often lie on a part of the condyle that can only be seen on an AP when the knee is flexed, thus tunnel and patellar views should also be obtained.
Once the diagnosis is made, two important diagnostic tasks remain. First, radiographs of the opposite knee must also be obtained as the disease is bilateral in about 30% of cases. Second, an MRI is often indicated to assess the stability of the lesion. Breaks in the articular surface, cysts, and fluid beneath the lesion are all signs of instability.
The main determinates of treatment are patient age (i.e. growth remaining) and lesion stability.
1. Young patient with a stable lesion: Such a patient will have no symptoms of catching or locking and may even have had the diagnosis made through X-rays obtained for unrelated trauma. Children less than 10 years old may undergo spontaneous healing. For asymptomatic children in this age group, observation and follow up X-rays in 6 months may be adequate. The use of crutches with restriction to non-weight bearing for 6 to 8 weeks is often used for those with knee pain or who do not go on to heal with time. These children should be followed with repeat films at 3 and 6 months. If healing does not occur, surgery is necessary.
2. Patient with an unstable lesion: This patient will generally have mechanical symptoms and is often closer to skeletal maturity or has reached adulthood. Unstable lesions cannot heal spontaneously. As a result these patients require surgery to stabilize the fragment. Depending on the situation, biodegradable nails, metal screws, and bone graft may be needed. This treatment has greater morbidity and a lower success rate than simple drilling of a stable lesion.
Figure 4: This arthroscopic view of the lateral femoral condyle demonstrates a defect where the articular cartilage has broken free and become a loose body (not seen in this image).
Figure 5: This view after arthrotomy demonstrates fixation of the cartilage fragment in the defect of Figure 4 with restoration of the joint surface.
3. Patient nearing skeletal maturity with a stable lesion Recent literature has strongly supported the value of retrograde drilling of stable lesions prior to skeletal maturity. Furthermore, this technique seems to work best when there is considerable growth remaining. Thus the trend has been to operate on more stable lesions, and to do so at an earlier age. The rationale is that good results can be obtained in a high percentage of patients with a small arthroscopic procedure of low morbidity.
Figure 6: In a patient similar to figure 3, these images show the resolution of an OCD lesion of the medial femoral condyle 6 months following drilling.
4. Salvage procedures: For individuals unfortunate enough to have lost a portion of the joint surface through failed attempts at fixation or delay in diagnosis, a restoration of the surface can be attempted. Transplantation of plugs of adjacent cartilage can be successful, but creates some morbidity at the plug donor site. The use of allograft tissue addresses this issue, but donor cartilage viability has not been definitively proven. Finally, transplantation of autologous chondrocytes harvested arthroscopically has also been advocated.
Juvenile osteochondritis dissecans is a problem that begins in the subchondral bone of young people and can result in a cartilage fragment that catches or even breaks free as a loose body. Loss of articular cartilage has been shown to increase the likelihood of late arthritis. The goal is to preserve native cartilage if at all possible. Late salvage techniques are of value, but generally the best results are obtained with early diagnosis and treatment of stable lesions that are amenable to non-weight bearing conservative management or arthroscopic drilling.
- The healing potential of stable juvenile osteochondritis dissecans knee lesions. Wall EJ et. al. J Bone Joint Surg AM 2008 Dec: 90 (12): 2655-64
- Juvenile versus adult osteochondritis dissecans of the knee: appropriate MR imaging criteria for stability. Kijowski R et al Radiology 2008 Aug: 248(2) 571-8
- Extraarticular drilling for stable osteochondritis dissecans in the skeletally immature knee. Donaldson LD et al. J Pediatr Orthop. 2008 Dec; 28(8): 831-5
- Surgical management of juvenile osteochondritis dissecans of the knee. Trinh TQ et al. Knee Surg Sports Traumatol Arthrosc. 2012 Feb 11 (e pub ahead of print)