The pes anserine is an anatomical structure located on the inner aspect of the knee, below the joint line. It plays a role in knee movement and stability. This area can be a source of pain and discomfort.
Anatomical Overview
The pes anserine is found on the anteromedial (front and inner) surface of the proximal tibia (shin bone), approximately 5 cm below the medial knee joint line. It is a conjoined tendinous insertion, formed by the merging of tendons from three muscles: the sartorius, the gracilis, and the semitendinosus. The term “pes anserine” is Latin for “goose’s foot,” named for the web-like, three-pronged appearance of these conjoined tendons.
The sartorius tendon is most anterior, followed by the gracilis in the middle, and the semitendinosus most posterior. These tendons lie superficial to the medial collateral ligament (MCL) of the knee. Beneath these tendons lies the pes anserine bursa, a fluid-filled sac that reduces friction and cushions the bones, tendons, and muscles, allowing for smooth movement.
Function and Importance
The sartorius, gracilis, and semitendinosus muscles, through their insertion at the pes anserine, contribute to lower limb movements. They primarily flex the knee (bend the knee joint) and contribute to hip adduction (bringing the leg closer to the midline).
The pes anserine complex also assists in internal rotation of the tibia. Beyond movement, these muscles and their conjoined tendon are important for knee stability. They resist valgus forces (forces that push the knee inward), helping prevent a “knock-knee” appearance. This arrangement also helps stabilize the pelvis over the knee joint during movement.
Common Conditions
The pes anserine region can be affected by several conditions, often involving inflammation. Pes anserine bursitis is inflammation of the bursa beneath the conjoined tendons. This condition typically causes pain and tenderness on the inner side of the knee, usually 2 to 3 inches below the knee joint. The pain often develops gradually and may worsen with activities such as climbing stairs, getting up from a seated position, or during physical activity.
Pes anserine tendinopathy is inflammation or degeneration of the tendons. Distinguishing between bursitis and tendinopathy can be challenging due to their close proximity; “pes anserine syndrome” often encompasses both. Factors contributing to these conditions include:
- Overuse from repetitive knee movements (e.g., running, cycling)
- Direct trauma to the area
- Tight hamstring muscles
- Certain medical conditions (e.g., osteoarthritis, obesity)
- Abnormal knee alignment (e.g., knock-knees)
Management Approaches
Management for pes anserine conditions typically focuses on non-surgical methods to reduce pain and inflammation. Initial approaches involve rest from aggravating activities and applying ice for 15-20 minutes, several times daily, to reduce inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) can also be used to alleviate pain and swelling.
Physical therapy is often recommended, focusing on exercises to stretch and strengthen knee muscles, particularly hamstrings, quadriceps, and hip adductors. Activity modification, adjusting movements or training techniques, is also important to prevent recurrence. If conservative treatments are insufficient, corticosteroid injections may be considered. These deliver anti-inflammatory medication directly into the bursa or around the tendons for targeted pain relief, often with ultrasound guidance for precision.