Plantaris

A small muscle located in the posterior compartment of the leg, it plays a role in plantarflexion of the foot.

The plantaris is a slender muscle that runs along the posterior side of the leg. It originates from the lateral supracondylar ridge of the femur above the knee joint and inserts into the achilles tendon. Due to its small size, it is often considered a vestigial muscle, meaning that it has lost its original function over time.

Terminologia Anatomica

musculus plantaris

System

Musculoskeletal system

Function

The primary function of the plantaris muscle is to assist in plantarflexion, which is the action of pointing the toes and extending the foot downward. This action is crucial during activities such as walking, running, and jumping, where the feet push off the ground. Although the plantaris muscle is capable of contributing to these movements, it is not essential for normal function, as other muscles, such as the gastrocnemius and soleus, more significantly perform plantarflexion. The plantaris may also play a minor role in knee flexion due to its proximal attachment to the femur, although this function is secondary and less prominent than its role in foot movements.

Location

The plantaris muscle is located in the posterior compartment of the leg, which is situated between the knee and ankle joints. It lies deep beneath the gastrocnemius muscle, which is the larger calf muscle that gives the leg its shape. The plantaris runs along the lateral aspect of the leg just above the soleus muscle. The tendon of the plantaris travels medially and joins the Achilles tendon, which inserts into the calcaneus (heel bone) at the back of the foot. This anatomical positioning allows the plantaris to assist in foot movement while also being closely associated with other significant muscles in the calf region.

Did You Know?

The plantaris muscle is often referred to as the 'freshman nerve' because those studying anatomy commonly struggle to locate it during dissection, leading to the misconception that it is non-essential.
Some people are born without a plantaris muscle, and their walking and physical abilities are not adversely affected, which indicates its non-critical function.
The tendon of the plantaris is sometimes harvested for use in reconstructive surgery, especially for repairing ligaments, due to its similar properties to tendons in other critical areas.