Final answer:
X-ray is the preferred technique for the initial diagnosis of osteoarthritis of the knee.
Step-by-step explanation:
The preferred technique for the initial diagnosis of osteoarthritis of the knee is X-ray. X-rays are commonly used to visualize the bones and joint spaces in the knee and can show signs of osteoarthritis such as narrowing of the joint space and the presence of bone spurs. Other imaging techniques such as MRI or CT scan may be used to further assess the condition of the soft tissues and cartilage in the knee. However, X-ray is often the first-line imaging modality for diagnosing osteoarthritis.