A male infant aged 8 months presented for assessment of popping sounds in the left knee when lying on his back, with onset 2 days prior. The parents expressed it was “as if his knee were coming out”. No evidence of pain or any other associated symptoms.

The physical examination evinced audible clicks and apparent voluntary subluxation with knee flexion and extension (see video in Appendix B). The rest of the physical examination was normal.

Voluntary femorotibial subluxation is a rare condition in the paediatric population, and there are few previous publications on the subject.1,2 It usually manifests in young children, with episodes of audible clicks in one or both knees that usually happen when the child is tired or upset. Although its presentation is striking and tends to scare parents, in most cases it is a benign condition that resolves spontaneously without sequelae. In some cases, the knee needs to be immobilized for a period of variable duration. It is important to know this condition to differentiate it from diseases that do require treatment, such as congenital dislocation of the knee or meniscus injuries or diseases.

Our patient was assessed with a radiograph, which was normal. In the subsequent follow-up, episodes became increasingly infrequent until they disappeared altogether, and there was no need for orthopaedic treatment.