Semimembranosus

The semimembranosus is part of the hamstring group of muscles, located in the posteromedial compartment of the thigh. It is a broad, flat, and membranous muscle located beneath the slender semitendinosus.

Name origin:

The word ‘semimembranosus’ originated from Latin, in which

‘Semi’ means partially
‘Membranous’ means membrane-like.

As the name suggests, this muscle has a broad and membranous tendon in contrast to the semitendinosus tendon, which is long, round, and slender.

Anatomy:

Image Created By: Malathi

Proximal attachment:

The semimembranosus proximally attaches to the superolateral facet of the ischial tuberosity, along with other hamstring muscles.

Distal attachment:

Distally, the semimembranosus attaches to the posteromedial aspect of the medial tibial condyle.

Nerve innervation:

Nerve innervation for the semimembranosus comes from the tibial component of the sciatic nerve (L5-S2).

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

The semimembranosus crosses both the hip and knee joints, making it a two-joint muscle, and so, it has action in both joints.

Concentric (shortening) action:

Standard mover action:(distal attachment moving towards proximal)

At the Knee joint:

The semimembranosus muscle flexes the leg at the knee joint, along with other hamstring muscles.
Being the major part of the medial hamstrings, it rotates the tibia medially relative to the femur when the knee is flexed.

At the Hip joint:

The semimembranosus produces extension at the hip joint.
Additionally, it internally rotates the thigh at the hip.

Reverse mover action:(proximal attachment moving towards distal)

At the Knee joint:

The semimembranosus can flex the thigh at the knee joint, along with other hamstring muscles, such as the biceps femoris and semitendinosus. The reverse mover action at the knee joint is uncommon yet essential.

At the Hip joint:

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

Eccentric (lengthening) action:

The semimembranosus contributes to the control and deceleration of the knee joint extension.
It controls and slows down the flexion at the hip joint. Additionally, it also contributes to the controlled anterior pelvic tilt.

Isometric function:

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

Purpose:

The semimembranosus (along with other hamstrings) plays a vital role during walking, and mainly during sprinting, jumping, and climbing.
During activities like walking and sprinting, the semimembranosus contracts eccentrically during the swing phase to prevent the knee from overextending as the heel strikes the ground. This reduces the load on the ACL ligament by helping to control the anterior translation of the tibia, thereby preventing ACL injury.
The semimembranosus helps stabilize the pelvis, hip, and knee as well. It stabilizes the pelvis by maintaining a posterior pelvic tilt. It provides posteromedial stability to the knee joint through its tendinous expansions that reinforce the posterior knee joint capsule.
Of the three hamstring muscles, the semimembranosus tendon directly plays a role in the knee joint stability, as the distal tendon diverges into several ligaments, capsule, and fascia.

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.