Congenital absence of the quadriceps is an extremely rare condition whose management is not standardised. The objective of this study was to describe the clinical presentation, treatments, and outcomes of a multicentre cohort.

Classification of the type of abnormality at birth helps to guide management decisions.

Fifteen patients (19 knees) were included retrospectively in this multicentre study. Data on joint range-of-motion and management were analysed. We divided the patients into three groups based on whether they had continuous hypoplasia (involving the entire quadriceps), discontinuous hypoplasia (hypoplasia of some of the muscle groups or aplasia of the distal third of the quadriceps), or aplasia (complete absence of the quadriceps with replacement by fat).

Physiotherapy was provided initially to all patients. The main treatment in the 6 patients with continuous hypoplasia was posterior release and biceps femoris lengthening. At last follow-up all 6 patients were able to walk unaided, although 4 of them had persistent knee extension lag. Quadriceps reconstruction and osteotomy to correct knee recurvatum deformity were performed in most of the 11 patients with discontinuous hypoplasia. Among them, 10 were able to walk unaided at last follow-up, and 5 had knee extension lag. The 2 patients with aplasia required knee arthrodesis after multiple surgical procedures. Both were able to walk.

Depending on the classification of the abnormality at birth, different surgical procedures should be considered. Surgery should only be performed after non-operative treatment. The treatment goal is to obtain a normal mechanical axis of the limb with the knee in extension and no extension lag, in order to enable walking.

IV, retrospective observational study.