The normal AP (Anteroposterior) view of the knee provides a frontal image of the knee joint and its surrounding bony structures. Here's a detailed description of the normal image appearance:

Bony Structures

1. Distal Femur:

   • The femoral condyles appear symmetrical.

   • The cortex is smooth and continuous without any irregularities or erosions.

   • Trabecular patterns within the bone are normal and evenly distributed.

2. Proximal Tibia:

   • The tibial plateau is visible and flat.

   • The medial and lateral tibial condyles appear symmetric.

   • No evidence of sclerosis, fractures, or lytic lesions.

3. Patella:

   • Only partially visible in the AP view, usually projecting over the distal femur.

   • The borders are smooth, with no irregularities or fractures.

4. Fibula:

   • The fibular head is visible lateral to the tibia and distal to the lateral tibial plateau.

Joint Space

1. Femoral-Tibial Joint Space:

   • Uniform and symmetric on both the medial and lateral sides.

   • The space should be free of narrowing, which could indicate cartilage loss.

2. Patellofemoral Joint:

   • Partially visible on the AP view but better evaluated in lateral or sunrise views.

an osteochondroma is present on the lower femur, the appearance on an AP knee X-ray would include the following key findings:

Bony Appearance

1. Exophytic Bony Growth:

   • A bony projection is seen extending from the metaphyseal region of the distal femur.

   • The lesion typically grows away from the knee joint (a hallmark feature of osteochondromas).

2. Cortical Continuity:

   • The cortex of the lesion is continuous with the cortex of the femur, which is a critical diagnostic feature.

   • The medullary cavity of the osteochondroma is also in continuity with the medullary canal of the femur.

3. Surface Characteristics:

   • The lesion may have a lobulated or irregular surface.

   • Calcifications might be visible, especially in the cartilaginous cap (if it is thick enough to calcify).

4. Size and Orientation:

   • The size of the lesion varies but is typically elongated.

   • Its orientation is usually directed away from the growth plate

Joint Space

• The femorotibial joint space remains intact unless the osteochondroma causes mechanical compression or degenerative changes due to its size or location.