Introduction and purpose: Femoral osteochondritis dissecans (OCD) is a process of unpredictable clinical course and uncertain aetiology (vascular, post-traumatic or microtraumatic). Its prognosis is based on diagnostic imaging (MRI and scintillation scanning) and age (Multicentre EPOS OCD Study). In our study we analysed the influence of the alignment of the lower limbs in femoral OCD.

Materials and methods: From 2000–2004 we studied 22 cases in 19 patients with femoral OCD. We carried out a tele-radiographic study of the lower limbs with weight-bearing, recording the location of the OCD according to Cahill, the femorotibial angle (n=87.5° ±2°) and the mechanical axis of the limb, which was considered normal when it went through the two tibial spines (Cahill zone 3).

Results: The mean age was 13.4 years (r: 10–28). The OCD was located in the medial condyle in 16 cases and the lateral in 6. We found changes in the femorotibial angle in 12/22 (55%) and of the mechanical axis in 18/22 (82%). In the cases with worst prognosis and loose bodies (7 cases), 100% showed changes in the mechanical axis.

Conclusions: There is a strong relation between OCD and changes in the lower limb alignment. The most sensitive radiological measurement is the mechanical or weight-bearing axis. This finding confirms the good prognosis of the lesion in children, since they undergo physiological changes in the femorotibial angle and constant changes of the mechanical axis until growth is complete.