The human foot is an intricate structure, designed for supporting body weight, enabling movement, and absorbing impact. It comprises 26 bones, 33 joints, and over a hundred muscles, tendons, and ligaments, all working in concert. Understanding the individual bones, like the navicular, helps to appreciate the foot’s overall functionality and mobility.
Locating the Navicular Bone
The navicular bone is situated on the inner side of the foot, forming part of the midfoot region. It is found just above the arch, on the medial (inner) aspect, in front of the ankle bone, the talus. This bone is located behind the three cuneiform bones and next to the cuboid bone on the outer side of the foot. A prominent bump, called the navicular tuberosity, can often be felt on the inferomedial (lower-inner) aspect of the navicular bone, slightly in front and below the inner ankle bone (medial malleolus).
Understanding the Navicular Bone
The navicular bone is one of the seven tarsal bones found in the foot. Its name, derived from the Latin “navicula,” refers to its characteristic boat-shaped or pyriform appearance. This shape is evident in its concave surface articulating with the talus. The navicular bone has articular facets on its anterior surface that connect with the three cuneiform bones: the medial, intermediate, and lateral cuneiforms. It also articulates proximally with the head of the talus.
Function of the Navicular Bone
The navicular bone plays a significant role in the biomechanics of the foot, particularly in maintaining its structural integrity. It is described as the “keystone” of the medial longitudinal arch, which is the arch running along the inner side of the foot. This positioning allows it to help distribute weight and forces across the foot during various activities.
The bone’s involvement in the medial longitudinal arch is important for shock absorption when walking, running, or standing. It acts as a structural link, connecting the hindfoot to the forefoot. The tibialis posterior tendon, which is the only muscle to attach directly to the navicular bone, further supports the medial arch and aids in foot stability.
Common Conditions Involving the Navicular Bone
Several conditions can affect the navicular bone, sometimes causing pain and limiting mobility. A navicular stress fracture is a tiny crack in the bone often caused by repetitive stress, common in athletes due to activities like running and jumping.
Accessory Navicular Syndrome involves an extra bone or piece of cartilage, known as an accessory navicular, present next to the navicular bone. This accessory bone is congenital, meaning it is present from birth, and while often asymptomatic, it can cause pain if irritated by trauma, chronic friction from shoes, or excessive activity. Symptoms typically include a visible bump, redness, swelling, and pain on the inner side of the foot, especially during or after activity.
Kohler’s Disease is a rare condition primarily affecting children. It involves a temporary disruption of blood supply to the navicular bone, leading to its temporary softening or flattening. This can cause pain, swelling, and a limp, as the child may try to walk on the outer side of the foot to alleviate discomfort.