Semitendinosus

The semitendinosus is one of the three muscles in the hamstring group, located in the posteromedial compartment of the thigh. It is a slender muscle with a long, cord-like tendon.

Name origin:

The semitendinosus originated from Latin, in which

‘Semi’ means partially
‘Tendinosus’ means tendon-like

It got this name because the muscle belly transitions into a long, round tendon approximately two-thirds of the muscle length, making it appear to be partly tendinous.

Anatomy:

Proximal attachment:

The semitendinosus proximally attaches to the ischial tuberosity, along with other hamstring muscles.

Distal attachment:

Distally, it joins with the sartorius and gracilis as the pes anserine tendon (goose foot tendons) and attaches to the anteromedial surface of the proximal tibia.

Nerve innervation:

The semitendinosus gets its innervation from the sciatic nerve (L5-S2), especially the tibial component.

Blood supply:

Arterial supply:

For the proximal one-third: inferior gluteal artery
For the middle one-third: Deep femoral artery (profunda femoris artery)
For the distal one-third: popliteal artery

Venous drainage:

Inferior gluteal vein, deep femoral vein, and popliteal veins

Function

Being a two-joint muscle (crossing the hip and knee joints), the semitendinosus has action in both joints.

Concentric (shortening) action:

Standard mover action:(distal attachment moving towards proximal)

At the Knee joint:

The semitendinosus muscle flexes the leg at the knee joint, along with other hamstring muscles.
Being the medial hamstring, it is also capable of producing the medial rotation of the tibia, relative to the femur, when the knee is flexed.

At the Hip joint:

The semitendinosus contributes to hip extension.
It can adduct the thigh and additionally rotate the thigh at the hip joint by producing internal rotation of the hip.

Reverse mover action:(proximal attachment moving towards distal)

At the Knee joint:

The semitendinosus can flex the thigh at the knee joint along with other hamstring muscles when the leg is fixed (example: Bringing the body up from the Nordic curl). The reverse mover action at the knee joint is uncommon yet essential in certain situations.

At the Hip joint:

The Semitendinosus helps produce posterior pelvic tilt at the hip joint.

Eccentric (lengthening) action:

The semitendinosus contributes to the control and deceleration of the knee joint extension. Example: during the swing phase of a sprint, Nordic curl.
It slows down the flexion at the hip joint. Additionally, it also contributes to the controlled anterior pelvic tilt.

Isometric function:

The semitendinosus helps to stabilize the hip joint and the pelvis. It also helps stabilize the knee joint medially, along with the semimembranosus and the pes anserine tendons.

Purpose:

The main purpose of the semitendinosus (along with other hamstrings) is to help with walking, and mainly during sprinting, jumping, and climbing.
During activities like walking, sprinting, when the leg swings forward, it contracts eccentrically to slow the thigh and prevent the knee from overextending while the heel strikes the ground. This helps in deloading the ACL ligament and preventing its injury.
The semitendinosus helps in providing stability to the pelvis by maintaining a posterior pelvic tilt, and it also provides posteromedial stability to the knee joint, along with the semimembranosus.
Of the three hamstring muscles, the semitendinosus tendon is the common choice as a graft for ACL reconstruction surgery. This is attributed to the following reasons,
- It has a strong and long tendinous part.
- It is easily accessible as the tendon lies superficially at the pes anserinus, which makes it easy to harvest with relatively small incisions.
- Taking the semitendinosus tendon for ACL graft will have minimal functional deficit, as its role can be compensated by other hamstrings (biceps femoris and semimembranosus)

Azarudheen

Azarudheen is a passionate physiotherapist and exercise prescriptor with a deeply rooted belief in the transformative power of movement and education. His journey began in 2013 as a first-year physiotherapy student, balancing academics with part-time work to support his ambitions. Early in his career, he sought practical experience and began working at a fitness center, eventually transitioning into roles that expanded his knowledge and skill set in both clinical practice and teaching.

Driven by a relentless curiosity and desire for growth, Azarudheen took on an anatomy tutor position, believing in the value of continuous learning. A pivotal turning point came with his experience in cardiopulmonary rehabilitation at PSG Hospitals, where he worked closely with lung transplant patients. This experience emphasized the life-changing impact of functional movement and patient education, inspiring him to dive deeper into respiratory and cardiovascular physiology.

With strong support and belief in his vision, Azarudheen pursued a Master’s in Exercise and Sports Science at Manipal University—choosing it over conventional MPT programs to focus more on biomechanics, exercise physiology, strength and conditioning, and lifestyle health. His dedication was evident as he spent late nights at the library, worked part-time in gyms and cricket academies, and honed his craft through practical application.

In 2022, despite initial doubts, he opened his first clinic in his hometown—an act of courage and self-belief supported by his family and mentors. Built from the ground up, this clinic marked the start of a new era. Today, Azarudheen leads a growing team of 21 physiotherapists across two thriving clinics in Chennai and Coimbatore. His philosophy centers on patient education, movement optimization, and professional growth, and he continues to evolve both as a clinician and a leader.

Azarudheen’s journey reflects the power of perseverance, vision, and lifelong learning. He is not only a practitioner but also a mentor and advocate for a more thoughtful, movement-centered approach to healthcare.