Pain from the knee joint may be caused by signals from sensory nerves located in the bone itself. In a joint, the ends of bones are covered by a smooth tissue called cartilage. The layer of bone directly beneath this cartilage is called subchondral bone. The nerve supply to this subchondral bone, known as intrinsic innervation, originates from nerves located outside the bone.

These external nerves, along with blood vessels, enter the bone's interior through small openings on its surface called nutrient foramina. By targeting the external nerves before they pass through these openings, it may be possible to interrupt pain signals coming from within the bone. To do this effectively, it is necessary to understand the typical locations of these nutrient foramina. This study of bones aimed to map and measure the distribution of these openings on the lower part of the femur (the thigh bone), which forms the top part of the knee joint. This information could help improve procedures designed to disable nerves for pain relief, a process called denervation.

Researchers used a collection of 19 human thigh bones for this analysis. They took standardized photographs of the lower end of each bone from three different angles: the side facing away from the body (lateral), the side facing toward the body (medial), and the front (anterior). The location of every nutrient foramina at the end of the bone (known as epiphyseal nutrient foramina) was recorded from these images. A software program called ImageJ was then used to precisely measure the distribution of these openings.

The study found that the locations of the nutrient foramina on the lower end of the thigh bone were varied.

On the lateral (outer) side, the area was divided into four equal sections, or quadrants. The foramina were distributed with 11.5% in the first quadrant, 44.7% in the second, 36.5% in the third, and 7.3% in the fourth. This shows a concentration of these openings in the second and third quadrants.

On the medial (inner) side, which was also divided into four quadrants, the distribution was 12.4% in the first quadrant, 40.4% in the second, 35.5% in the third, and 11.5% in the fourth. Similar to the lateral side, the foramina were most concentrated in the second and third quadrants.

When viewed from the front, the area was split into two halves. A significant majority of the foramina, 71.1%, were located on the medial (inner) half, while the remaining 28.9% were on the lateral (outer) half.

The nutrient foramina at the end of the femur are critical channels that allow external nerves to reach and supply the subchondral bone. The findings on the specific locations and distribution patterns of these openings can be used to improve medical techniques like nerve blocks and denervation procedures. This knowledge may help optimize treatments for managing chronic knee joint pain caused by conditions such as osteoarthritis.