Angular, rotational and gait variants — formative SAQs

SAQ 1 (10 marks) — The bowlegged two-year-old

Stem: A mother brings her two-year-old son to the clinic because his legs are still bowed and his feet turn in when he walks. He walked at eleven months, he is otherwise well, and his growth and milestones are normal. On examination the bowing is symmetric, painless, and the intercondylar distance is four centimetres; his feet intoe and the thigh-foot angle is negative. Outline your assessment, the developmental basis, and your management. [1] [4]

Model answer

Assessment and placement on the developmental curve (3 marks). This child has two overlapping normal variants — physiologic genu varum resolving and internal tibial torsion. The Salenius and Vankka curve shows the leg is bowed at birth, straightens to neutral around two years, then develops physiologic valgus peaking at three to four years. A symmetric, painless bowing at age two with a normal gait onset sits on the curve. The negative thigh-foot angle locates the intoeing at the tibia, the typical site for the toddler, and the rotational profile places the torsion on the limb. [1] [3]

Red-flag screen (2 marks). I screen for the features that move a bowleg off the developmental curve: progression after two years, asymmetry or unilateral bowing, pain, short stature, dysmorphism, and a delayed walking. This child is symmetric, painless, walked on time, and has normal growth and milestones, so the screen is negative. A positive screen would redirect to a weight-bearing radiograph and the measurement of the proximal tibial metaphyseal-diaphyseal angle to exclude infantile Blount disease, and to biochemistry if rickets were suspected. [4] [9]

Management (5 marks). The management is observation, reassurance, and a safety-net. No brace, no special shoe, and no orthotic is indicated, because the contemporary evidence confirms these devices do not speed the correction of intoeing. I counsel the family on the developmental curve and the expected timeline, I measure and document the intercondylar distance and the thigh-foot angle with a photograph for follow-up, and I review in six to twelve months. I teach that sitting cross-legged is encouraged for the tibial torsion. I give a clear safety-net to return if the bowing worsens, becomes asymmetric, or if any pain or limp emerges. [3] [4]

SAQ 2 (10 marks) — The progressive asymmetric bowing in a three-year-old

Stem: A three-year-old boy is referred because his bowing has worsened over the past year and is more marked on the left. He walked at ten months and his body mass index is above the ninety-fifth centile. He is otherwise well. On examination the left tibia bows progressively below the knee. Outline your assessment, the differential, the investigation, and your management. [9] [11]

Model answer

Assessment and the red flag (3 marks). This is not a physiologic variant. The bowing is progressive, it is worse after the age of two when the physiologic varus should be resolving, and it is asymmetric. The early walking, the obesity, and the progressive unilateral bowing are the recognised risk factors and presentation of infantile Blount disease, the pathologic mimic that the bowleg assessment exists to catch. The red-flag screen is positive on progression, asymmetry, and unilateral involvement. [9] [3]

Differential and investigation (4 marks). The leading diagnosis is infantile Blount disease. A weight-bearing anteroposterior radiograph of the lower limbs is the first-line investigation, and I look for the medial proximal tibial beaking, the fragmentation of the medial growth plate, and the metaphyseal-diaphyseal angle above about eleven degrees that supports the diagnosis. I measure the mechanical axis and compare the two sides. I consider rickets in the differential, and if the stature is short or the dietary history suggests a deficiency, I check the calcium, phosphate, alkaline phosphatase, parathyroid hormone, and vitamin D, and I review the physes for the widening and cupping of the metabolic bone disease. [9] [11]

Management (3 marks). I refer to the paediatric orthopaedic surgeon. The early Blount disease may be treated with a knee-ankle-foot orthosis, and the progressive disease is treated with a proximal tibial osteotomy to correct the mechanical axis and prevent the permanent deformity. The adult-function study confirms that the late-treated Blount disease leaves a lasting burden, so the early recognition and referral are the key. If rickets is confirmed, I involve the endocrine team for the correction of the metabolic defect alongside the orthopaedic management. I counsel the family honestly on the diagnosis and the plan. [9] [3]