We describe a rare form of congenital snapping knee. In six knees in four children, the tibia subluxed anteriorly on the femur when the knee was extended and reduced spontaneously on flexion. The abnormal movements were seen and felt as sudden snaps or clunks at about 30 degrees of flexion. All six knees showed similar dysplastic features, although the patients had different clinical syndromes. The mechanism of the subluxation and its management are discussed.

We studied the morphology of the contralateral femur in 10 patients with subcapital fractures, 10 with trochanteric fractures and 10 with unilateral osteoarthritis. We found that the patients with trochanteric fractures had a significantly shorter femoral neck (4.5 +/- 0.5 cm) than patients with subcapital fractures or osteoarthritis (5.4 +/- 0.4 cm). It may be that this difference in femoral neck length is related to the site at which a proximal femoral fracture occurs.

Quantitative polarised light microscopy was applied to sections of unfixed, undecalcified bone taken at operation from patients with two types of proximal femoral fracture, subcapital and trochanteric. Specimens were also taken from the equivalent sites in otherwise normal subjects at autopsy, and from various other sites of traumatic fractures; these two latter groups acted as controls. Analysis of the 57 specimens disclosed changes in the nature of the bone at the site of subcapital fractures, namely the presence of relatively large crystals of hydroxyapatite and a change in the molecular orientation, but not total content, of the acidic proteoglycans of the bone matrix. Our results have confirmed and extended the findings of others on subcapital fractures, and have also shown very similar changes in the trochanteric fractures. It thus appears that the bony changes in the two types of proximal femoral fracture are not as different as has been suggested.

Aspergillus infection of the spine is rare; for it to lead to paraplegia is still more rare. When this does occur it is usually treated by decompression and antifungal agents, but the results have usually been poor. We report two cases of successful conservative treatment of Aspergillus paraplegia in patients with chronic granulomatous disease.