What causes knock knees?

The medical term is genu valgum. When standing with the knees together, the lower legs angle outward and the ankles remain apart. The appearance may come from the alignment of the thigh bone, shin bone, or both rather than from the knee joint alone.

Leg alignment changes naturally as children grow, and a symmetrical knock-kneed phase can occur without disease. It usually becomes less noticeable as development continues. Family body shape can also influence alignment.

A pronounced, worsening, one-sided, or persistent deformity may be related to altered growth around the knee, a previous fracture or growth-plate injury, or a disorder affecting bone strength or development. In adults, joint wear or an old injury may change the leg axis. Alignment cannot be explained reliably from appearance alone.

If a child is comfortable, active, and the alignment looks similar on both sides, observe how it changes over time rather than repeatedly correcting the child's stance. Shoes, insoles, or exercises do not straighten a bone that is growing at an altered angle.

Physiotherapy can address strength, balance, movement skills, or discomfort when those are concerns, even though exercise may not change the underlying bony alignment. A clinician may examine standing posture, walking, hip rotation, leg lengths, and growth pattern before deciding whether imaging or specialist review is useful.

Arrange assessment if the angle is clearly different between the legs, becomes more noticeable rather than less, begins after an injury, or is accompanied by pain, swelling, limping, frequent falls, reduced activity, or short stature relative to the child's established growth pattern.

Prompt care is needed when a new deformity follows significant trauma, the child cannot bear weight, or the leg is severely painful or swollen. Adults should seek evaluation for newly changing alignment, especially with worsening knee pain or loss of function.

Ask whether the alignment fits the expected developmental pattern, whether both legs are affected equally, what changes should be monitored, whether an underlying bone or growth problem needs investigation, and what treatment would target.