A 6-year-old boy presented to the orthopaedic clinic, referred from his general practitioner after his mother noted an apparent shortening of the left leg, in toeing of the left foot and a waddling gait. No sinister symptoms were described. On examination there was a half-centimetre shortening in the femoral component of the left leg.

An X-ray of the pelvis and left femur revealed multiple lucent lesions in the left hemipelvis and the femoral metaphysis and diaphysis with a predilection for the lateral bone (figures 1 and 2). The left hemipelvis lesion demonstrated the characteristics of large chondroid lesions with thinning of the lateral cortex. The left femur contained multiple lucent lesions and a ‘celery stalk’ appearance of the lateral distal metaphysis, valgus deformity and thinning of the lesser trochanter cortex. A radiographic skeletal survey revealed further lesions of the proximal left tibia (figures 3 and 4), with an additional lucent lesion in the ipsilateral third metatarsal (figure 5).