What is osteochondritis dissecans of the knee in children?

Osteochondritis dissecans (OCD) is an acquired condition affecting a portion of the bone just beneath the articular cartilage in the knee. It is believed that one of the reasons for the development of OCD is repetitive microtrauma, resulting in stress fractures of the bone and subsequent softening of the adjacent articular cartilage. Due to repetitive stress, the fractured area fails to heal, leading to necrosis of the bone. Over time, the affected bone, along with the overlying cartilage, becomes unstable within its bed or even detaches, forming a loose body within the joint. Perhaps because boys are more involved in sports activities, OCD of the knee occurs four times more frequently in boys than in girls. Sometimes OCD develops simultaneously in both knees. If OCD of the knee is not recognized and treated in a timely manner, it can lead to further deterioration of bone and cartilage in the joint, eventually resulting in improper alignment of joint surfaces and the development of osteoarthritis.

How to diagnose osteochondritis dissecans of the knee in children?

The clinical presentation of OCD of the knee in children is nonspecific. Children typically complain of activity-related pain or restricted knee mobility with occasional swelling. Sometimes, children report a sensation of something “moving” in their knee, which may be a piece of detached cartilage moving within the knee. During the clinical examination by a pediatric orthopedic surgeon, tenderness over the site of OCD is usually found if palpable. Tests assessing the range of motion in the knee may reveal catching during movement. If OCD of the knee is suspected, X-ray imaging in two planes, with additional tunnel views of the knee, should always be performed. On X-rays, OCD appears as a detached elongated bone fragment in the concave bed, Figure 1. In addition to X-ray imaging, when OCD of the knee is suspected, the child should undergo magnetic resonance imaging (MRI) of the knee. The most critical information observed in knee MRI includes the condition of the articular cartilage (whether it is intact or disrupted), the state of the bone beneath the cartilage (presence of cystic formations and intramedullary fluid), the stability of the OCD, and the identification of any associated knee pathology. For example, an irregular, discoid meniscus often causes OCD in the knee.

How to treat osteochondritis dissecans of the knee in children?

The choice of treatment for OCD of the knee in children depends largely on the extent of bone and cartilage damage on one hand and the child’s skeletal maturity on the other. Therefore, correctly assessing the child’s skeletal maturity, i.e., estimating the remaining growth potential, is crucial. In younger children with open growth plates, there is a significant chance that OCD can heal conservatively without surgery. In such cases, sports activities or any repetitive trauma to the knee should be prohibited for six months to a year, with monitoring through new MRI scans. During this period, vitamin D supplementation is recommended. However, if a follow-up MRI reveals unstable OCD in the bed or a loose fragment within the joint, or if the child is skeletally mature, a surgical procedure should be considered. The current standard of treatment is the arthroscopic fixation of an unstable OCD using screws or the debridement of the OCD bed with repair of cartilage defects, such as microfracture. During knee arthroscopy, the stability of the meniscus should be assessed, and if unstable, it should be sutured. Postoperative rehabilitation includes partial weight-bearing with crutches and gradual leg loading. In cases involving meniscus repair, there is a gradual increase in the range of motion. The overall prognosis is generally good for children after the stabilization of the OCD fragment due to their considerable healing potential. A full return to sports activities is expected after six months.

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