The aim of our study is to present osteoid osteoma as a disease in preschool children. O O is a benign inflammatory process that is characterized from osteoid formation. It appears mainly in the second and third decade of life, while before 5 years of age usually as case reports. The clinical and radiological presentation must be differentiated from trauma, osteomyelitis, malignancy and other benign diseases.

We present three patients, aged ranging from 18 months to 4 years old, that were treated surgically for the removal of O O in the tibia and fibula. All patients presented with limping, pain mainly in the night, gradual restriction of activities. The clinical, hematological and radiological investigation revealed the general aspects of the disease. Bone scans were positive in all. CT scan confirmed the diagnosis in all three patients. Surgical treatment was done with fluoroscopic assistance, in order to remove the minimum possible amount of bone. In two patients the lesion was located in the distal metaphysis of the tibia and in one in the distal metaphysis of the fibula.

The diagnosis was confirmed with the typical nidus, in pathological specimens. In one patient the lesion was intracortical and in two in the medullary area. Despite the ages of our patients, there were not misleading findings, in the specimens. After surgery the patients were symptoms free, and with 1–4 years follow up, there are no recurrences.

We conclude that osteoid osteoma must be included in the differential diagnosis, in cases of pain and limping, in preschool children.

We studied the kinematic patterns of knee, performing gait analysis, in diplegic children. Our gait laboratory consists of 4 infrared cameras. We used the Elite program. We studied initially 25 normal children. We constructed our models and developed the linear measurements of the gait. Then we performed measurements of the angles of the knee and ankle joints and the wave forms of the kinematic forms of these joints.

We performed gait analysis in 25 diplegic children aged 4–15 years old. We found two groups of children. In the first group (21 children) the main lesion was in the kinematics of the knee and in the second group (4 children) in the ankle joint.

In the first group, characteristic pattern is the absence of full extension of the knee during stance. Analyzing the kinematics of the ankle joint of this group, we found 12 children with toe strike and 9 children landing in the whole foot. Studding the wave form of the knee in stance and swing, we separated those with spasticity alone from those with fixed contractures of the knee. Our patients were treated either with botulinum injections or with intamuscular lengthening, according to our results.

In the second group, of diplegic children with toe walking, we found increased equinus, both in stance and swing.

Kinematic studies of the knee in frontal and coronal level showed increased adduction of the femur( scissoring) and increased anteversion.

Gait analysis in diplegic children offers an accurate assessment of the gait disorders. We can plan our treatment according the results of the gait analysis.