1. General Principles & Basic Science MCQs

Which of the following muscles is considered the primary driver of limb advancement during the initial swing phase of the normal gait cycle?

A 25-year-old female presents with groin pain. Radiographs reveal a lateral center-edge angle of Wiberg of 12 degrees. How does this structural abnormality alter hip biomechanics compared to a normal hip?

During a normal human walking gait cycle at a standard pace, what percentage of the entire gait cycle is spent in double-limb support?

A 45-year-old active patient undergoes a medial opening wedge high tibial osteotomy (HTO) for medial compartment gonarthrosis. Assuming standard technique distal to the tibial tubercle, what are the most likely expected postoperative changes to the mechanical axis and patellar height?

When planning a lower extremity deformity correction, Osteotomy Rule 2 dictates that the osteotomy is performed at a level different from the center of rotation of angulation (CORA), while the hinge axis is placed directly at the CORA. What is the expected geometric result of this correction?

A patient undergoes a proximal femoral osteotomy that effectively lateralizes the greater trochanter without altering the position of the femoral head. What is the biomechanical effect on the required abductor muscle force and the hip joint reaction force during single-leg stance?

A 65-year-old male presents with a "steppage gait," characterized by excessive hip and knee flexion during the swing phase. This compensatory gait pattern is most commonly necessitated by a deficit in which of the following nerves?

During a normal gait cycle, the ankle joint transitions through varying degrees of dorsiflexion and plantarflexion. At which specific point in the gait cycle does maximal ankle dorsiflexion occur?

A 22-year-old male presents with chronic, mild knee pain. Radiographs reveal an eccentric, sharply circumscribed, osteolytic lesion with a sclerotic rim in the proximal tibial metaphysis.

What is the most characteristic histological finding for this lesion?

Which specific biochemical deficiency is responsible for the clinical presentation of Morquio A syndrome (MPS IVA)?

In a patient with confirmed Camurati-Engelmann disease experiencing significant, debilitating bone pain, what is the most effective first-line medical therapy?

A patient with newly diagnosed Primary Bone Lymphoma of the femur asks about their general prognosis and presentation. Which of the following statements is most characteristic of this disease?

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders. Which of the following features uniquely distinguishes Hunter syndrome (MPS II) from Hurler syndrome (MPS I)?

Morquio A syndrome (MPS IVA) is primarily caused by a deficiency in which of the following enzymes?

Which of the following histological features is most useful in differentiating a Chondroblastoma from a Chondromyxoid fibroma?

A patient with suspected Camurati-Engelmann disease undergoes radiographic evaluation.

What is the hallmark radiographic feature seen in this condition?

What is the most effective medical treatment to alleviate the severe bone pain and improve muscle weakness in patients with Progressive diaphyseal dysplasia (Camurati-Engelmann disease)?

A 35-year-old patient undergoes curettage of a pathologically confirmed Chondromyxoid fibroma of the proximal tibia. What is the standard management to minimize the risk of local recurrence while preserving joint function?