Section 01 of 20
Introduction
Semitendinosus lies superficial to semimembranosus on the inner back of the thigh. It is named for its unusually long, thin tendon, which begins about halfway down the thigh and continues to the inner side of the upper tibia, making the tendon roughly as long as the muscle belly itself.
Its tendon joins those of sartorius and gracilis to form the pes anserine (goose-foot) on the upper medial tibia, just below the knee. Along with biceps femoris and semimembranosus, it is one of the three hamstring muscles that cross both the hip and the knee.
Section 02 of 20
Origin
| Origin | The ischial tuberosity, by a tendon shared with the long head of biceps femoris. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 03 of 20
Insertion
| Insertion | The upper medial surface of the tibia, as part of the pes anserine, together with sartorius and gracilis. |
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An anatomical image for this section will be added when verified source media becomes available.
Section 04 of 20
Actions
| Primary action | Hip extension and knee flexion. |
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| Secondary actions | Medial rotation of the flexed knee and pelvic control. |
| Movement at the joint | Hip joint and knee joint. |
| Heads / fiber groups | Single muscle with a long cord-like distal tendon. |
| Functional examples | Walking and running (driving the leg back); climbing stairs; bending forward at the hips; decelerating a kick. |
Hip extension
Extends the thigh at the hip, as in driving the leg backward when walking or running.
Knee flexion
Bends the knee.
Medial rotation of the flexed knee
With the knee bent, helps rotate the lower leg inward.
Pelvic control
Helps control forward tilting of the pelvis during standing and movement.
Section 05 of 20
Nerve Innervation
| Nerve | Tibial division of the sciatic nerve, roots L5–S2. |
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The sciatic nerve runs beneath the hamstrings for most of the thigh. Pain that shoots down the back of the leg, or numbness and tingling in the leg or foot, may reflect nerve or disc involvement, not only muscle tightness.
Section 06 of 20
Blood Supply
| Blood | Perforating branches of the profunda femoris (deep femoral) artery, with the inferior gluteal artery supplying the upper part. |
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Section 07 of 20
Pictures and Visual Anatomy
An anatomical image for this section will be added when verified source media becomes available.
Section 08 of 20
Functional Movement
Semitendinosus is active in walking, running, climbing stairs, and bending forward from the hips. It helps decelerate the swinging leg before the foot strikes the ground and, through the pes anserine, helps steady the inner knee during activities that involve twisting or side-to-side movement.
Section 09 of 20
Synergists and Antagonists
Synergists: semimembranosus and biceps femoris (hip extension and knee flexion), and gluteus maximus (hip extension). Antagonists: the quadriceps (knee extension) and iliopsoas and rectus femoris (hip flexion).
Section 10 of 20
Palpation and Location
Client position and technique
Position the client prone with the knee slightly bent and supported. Locate the ischial tuberosity, then follow the medial hamstring mass down the thigh. The long, thin, cord-like tendon of semitendinosus becomes easy to feel in the lower third of the thigh, more superficial and rounder than the broader semimembranosus beneath it. Ask the client to bend the knee against light resistance to feel it tighten.
Protect nearby structures
The sciatic nerve runs through the middle of the back of the thigh, and the popliteal vessels and tibial nerve lie behind the knee. Avoid deep or sustained pressure directly behind the knee, use moderate pressure over the muscle belly, and stop if the client reports tingling, numbness, or sharp pain down the leg.
Section 11 of 20
Massage Therapy Relevance
The hamstrings, including semitendinosus, are commonly tight or strained in runners and sprinters, and its tendon contributes to pes anserine pain at the knee. Hamstring and knee symptoms have many possible causes, so careful assessment matters.
Section 12 of 20
Dysfunction: What Happens When Movement Goes Wrong
Changes in how a muscle works can change how a joint moves. The points below describe possibilities that may be associated with altered muscle function; they are not diagnoses, and one muscle is never assumed to be the sole cause of a problem.
When the muscle is weak
Weakness may reduce hip extension and knee flexion strength and may be associated with more work by the other hamstrings and gluteus maximus.
When it is tight or shortened
Tightness may be associated with limited hip flexion with the knee straight and a pulling sensation in the back of the thigh.
When it is overused
Repeated sprinting and deceleration may overload the muscle and tendon and may contribute to posterior thigh or knee pain.
When it is strained
A strain may cause sudden pain in the back of the thigh with sprinting or overstretching; sciatica and hip problems can look similar.
When it is inhibited or others compensate
Reduced activation may be associated with reduced control of knee flexion and more load on the knee ligaments.
When it does not coordinate well with synergists and antagonists
Poor coordination with the other hamstrings and gluteus maximus may alter hip and knee control and may be associated with hamstring or knee symptoms.
Section 13 of 20
Conditions, Pathologies, and Pain Relationships
Hamstring strain
Sprinting, sudden deceleration, and overstretching can strain semitendinosus, causing pain in the back of the thigh, sometimes with bruising.
Proximal hamstring tendinopathy
Overload of the shared tendon at the ischial tuberosity may cause deep buttock pain that is worse when sitting or during hip flexion with the knee straight.
Pes anserine pain syndrome
Pain and tenderness on the upper inner tibia below the knee may involve the pes anserine tendons, including semitendinosus, and their bursa.
Differential considerations
Sciatica, lumbar disc problems, hip joint disease, and medial meniscus or ligament injury of the knee can all cause pain in this region.
Section 14 of 20
Example Clinical Relationship
A soccer player reports tenderness on the inner side of the upper shin just below the knee that is worse after practice. The pes anserine tendons, including semitendinosus, may be involved, and the pattern may be associated with pes anserine pain syndrome, but knee joint and nerve problems can look similar. Gentle work along the medial hamstring may support comfort, while a sudden pop with bruising or a swollen warm leg needs referral.
Section 15 of 20
Massage and Treatment Approaches
For healthy, non-acute tissue, position the client prone with the knee slightly bent and supported. Begin with broad effleurage from the knee toward the buttock, then use gentle kneading and slow longitudinal strokes along the medial hamstring mass, avoiding direct pressure behind the knee and over a tender pes anserine.
| Movement | Use gentle passive knee extension and hip flexion stretches within comfort; do not force range or bounce. |
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| Regional work | Consider semimembranosus, biceps femoris, gluteus maximus, gracilis, and sartorius when assessment supports it. |
| Avoid | Deep pressure directly behind the knee, over an acute strain, near the ischial tuberosity if tender, or over a tender pes anserine. |
Section 16 of 20
Precautions and Contraindications
Precautions and contraindications
- Acute strain, suspected tear, or recent thigh or knee injury or surgery.
- Use caution with anticoagulant use, easy bruising, or varicose veins.
- Avoid deep pressure over the popliteal fossa (back of the knee).
- Stop if pressure causes sharp pain, numbness, or tingling down the leg.
Section 17 of 20
Red Flags and When to Refer
Red flags and referral
- Sudden severe thigh pain with a pop, bruising, and a palpable gap, or inability to bear weight (possible tear or avulsion).
- A swollen, warm, red, or painful calf or leg, especially on one side (possible blood clot).
- Numbness in the saddle area or bladder or bowel changes with back or leg pain.
- Progressive leg weakness, or thigh pain with fever or unexplained weight loss.
Section 18 of 20
Study Summary
Attachments
Origin: ischial tuberosity (shared with biceps femoris long head). Insertion: upper medial tibia (pes anserine).
Actions
Hip extension and knee flexion, with medial rotation of the flexed knee.
Supply
Tibial division of the sciatic nerve (L5–S2); perforating branches of the profunda femoris artery.
Section 19 of 20
Instructor Narration
Open narration transcript
Semitendinosus is a long, slender medial hamstring with an unusually long, cord-like tendon.
It arises from the ischial tuberosity, sharing a tendon with the long head of biceps femoris, and inserts on the upper medial tibia as part of the pes anserine, together with sartorius and gracilis.
It extends the hip and flexes the knee, and helps rotate the bent knee inward. Semimembranosus and biceps femoris help it, and the quadriceps and hip flexors oppose it.
The tibial division of the sciatic nerve supplies it, from L5 to S2, and perforating branches of the profunda femoris artery provide its blood.
Palpate with the client prone, follow the medial hamstring mass down the thigh, and feel the long, rounder cord-like tendon in the lower third, more superficial than semimembranosus. Avoid deep pressure directly behind the knee.
Hamstring strain, proximal tendinopathy, and pes anserine pain are common, and sciatica, disc, and knee joint problems can overlap. Refer a sudden pop with bruising and a gap, a swollen warm leg, saddle numbness, or progressive leg weakness.
Remember: ischial tuberosity to the pes anserine on the upper medial tibia; hip extension and knee flexion; tibial division of the sciatic nerve.
Section 20 of 20