Maximus Gage
The semimembranosus muscle is one of four posterior thigh muscles responsible for extending the hip. It is a long, unipennate type of skeletal muscle that spans the full length of the thigh, from the hip to the knee. The semimembranosus is a relatively large muscle that plays a role in hip extension and knee flexion. It acts synergistically with the popliteus muscle and is part of the hamstring muscle group, along with the semitendinosus and biceps femoris. The muscle is prone to inflammation from overuse, misuse, or trauma, and can be evaluated through specific tests targeting the knee and hip joints.
| Characteristics | Values |
|---|---|
| Origin | Ischial tuberosity |
| Insertion | Medial condyle of tibia |
| Action | Flexes and medially rotates leg at knee joint; extends thigh at hip joint |
| Innervation | Tibial division of sciatic nerve (L5-S2) |
| Arterial Supply | Perforating arteries of deep femoral artery |
| Synergistic Muscles | Popliteus muscle |
| Antagonists | Vastus Lateralis, Vastus Medialis, Vastus Intermedius, and Rectus Femoris |
| Agonists | Gluteus Maximus, Semitendinosus, Biceps Femoris (long head), and Adductor Magnus (posterior part) |
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What You'll Learn
- The semimembranosus muscle is one of four posterior thigh muscles
- It is a hip extensor and a knee flexor/intrarotator
- The muscle is innervated by the L5, S1 and S2 nerve roots
- The muscle is prone to inflammation from overuse, misuse, or trauma
- The semimembranosus is tested by flexing the leg at the knee joint against resistance
The semimembranosus muscle is one of four posterior thigh muscles
The semimembranosus muscle originates from the ischial tuberosity and inserts into the medial tibial condyle. The muscle is innervated by the tibial portion of the sciatic nerve (L5, S1, and S2 nerve roots). The femoral and popliteal arteries give off deep perforating branches that supply the semimembranosus muscle. The proximal tendon of the semimembranosus is long and flat, with a membranous appearance. The muscle fibres travel inferiorly and insert via a rounded tendon onto the medial condyle of the tibia.
The semimembranosus muscle flexes and medially rotates the leg at the knee and extends the thigh at the hip joint. It also provides support to the posterior knee joint through its fibrous extension, the oblique popliteal ligament. The semimembranosus tendon can be palpated by flexing the leg at the knee joint against resistance while lying in the prone position. This muscle is also associated with the semimembranosus insertion syndrome, a condition that causes severe pain when the attachment of the muscle is palpated at the posterior medial condyle of the tibia.
The semimembranosus muscle has a complex distal attachment with multiple arms, including the direct arm, the capsular arm, the oblique popliteal insertion, the anterior arm, and the inferior (popliteal) arm. This complex attachment makes the semimembranosus an important stabiliser of the posteromedial complex of the knee, particularly during knee flexion and internal rotation. Additionally, the semimembranosus works synergistically with the popliteus muscle through its fibrous extension.
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It is a hip extensor and a knee flexor/intrarotator
The semimembranosus muscle is one of four posterior thigh muscles responsible for hip extension. It is also a knee flexor/intrarotator. The muscle originates from the ischial tuberosity and inserts into a groove on the medial surface of the medial condyle of the tibia. The semimembranosus is a relatively long muscle that spans the full length of the thigh, from the hip to the knee. It is deep to the semitendinosus, superficial to the adductor magnus, and medial to the biceps femoris. The proximal part of the muscle is covered by the gluteus maximus and medial to the adductor minimus.
The semimembranosus is a hip extensor, which means it causes extension at the hip, pulling the upper torso into an erect position. It is also a knee flexor, which means it flexes and medially rotates the leg at the knee joint. The muscle is innervated by the L5, S1, and S2 nerve roots, which access the muscle through the tibial division of the sciatic nerve. The femoral and popliteal arteries give off deep perforating branches that supply the semimembranosus muscle, and occasionally, the inferior gluteal artery supplies its proximal part.
The semimembranosus muscle plays a crucial role in stabilising the knee joint, particularly during knee flexion and internal rotation. It also helps protect the medial meniscus from being crushed between the medial femoral condyle and the posterior medial tibial plateau during knee flexion. The distal semimembranosus complex stabilises the posterior capsule through the oblique popliteal ligament, which arises from the distal tendon of the semimembranosus. This ligament and the tendinous insertion of the muscle are prone to inflammation from overuse, misuse, or trauma.
The evaluation of the semimembranosus muscle strength is typically performed with the patient lying prone, with the knee extended. The patient actively flexes the knee while the therapist applies resistance through the distal tibia and fibula in the opposite direction of flexion. To focus specifically on the semimembranosus, it is useful to combine the knee bend with maintaining the tibia in internal rotation.
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The muscle is innervated by the L5, S1 and S2 nerve roots
The semimembranosus is one of four posterior thigh muscles responsible for extending the hip. It is a relatively long muscle that spans the full length of the thigh, from the hip to the knee. The muscle is innervated by the L5, S1, and S2 nerve roots. These nerve roots access the muscle through the tibial division of the sciatic nerve.
The L5 and S1 nerve roots are also referred to as lumbar and sacral nerve roots, respectively. They branch out from the spinal cord at each spinal segment, exiting the spinal cord through small bony openings (intervertebral foramina) on the left and right sides of the spinal canal. The L5 dermatome is an area of skin that receives sensations through the L5 spinal nerve and includes parts of the knee, leg, and foot. Similarly, compression or inflammation of the L5 and/or S1 spinal nerve root can cause radiculopathy or sciatica, resulting in pain, numbness, and weakness in the buttock, thigh, leg, foot, or toes.
The L5-S1 motion segment has a distinctive anatomy and is susceptible to higher mechanical stress and loads. This makes it more prone to traumatic injuries, degeneration, disc herniation, and nerve pain. If the pars of L5 fractures on both sides, it may slip over S1, a condition called spondylolisthesis. This condition is commonly observed in children and adolescents and is usually caused by repetitive stress.
The femoral and popliteal arteries supply the semimembranosus muscle with deep perforating branches. Occasionally, the inferior gluteal artery supplies the proximal part of the muscle. The semimembranosus acts in conjunction with the hamstring muscles and the popliteus muscle. It helps to stabilise the knee during flexion and extension and protects the medial meniscus from being crushed during knee flexion.
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The muscle is prone to inflammation from overuse, misuse, or trauma
The semimembranosus muscle is one of four posterior thigh muscles that are responsible for extending the hip. It is a relatively long muscle that spans the full length of the thigh, from the hip to the knee. The muscle is innervated by the L5, S1, and S2 nerve roots, which access the muscle through the tibial division of the sciatic nerve. The tendon of the semimembranosus appears at the level of the mid-thigh and continues toward the point of insertion at the medial condyle of the tibia.
The semimembranosus muscle is prone to inflammation from overuse, misuse, or trauma. This inflammation can lead to a condition known as semimembranosus insertion syndrome, which is characterized by localized tenderness over the posterior aspect of the medial knee joint and severe pain on palpation of the attachment of the muscle at the posterior medial condyle of the tibia. Overuse of the knee, aggressive exercise regimens, and direct trauma to the posterior knee are common causes of this syndrome.
Athletes are particularly susceptible to semimembranosus musculotendinous injuries (SMTI), and these injuries can result in a longer recovery time compared to other hamstring muscle injuries. The complex structure of the semimembranosus muscle, with its multiple adjacent muscular and neurovascular structures, may contribute to the challenge of treating SMTI.
Semimembranosus tendinopathy is another condition that can affect the muscle, causing chronic knee pain. This condition is thought to be more common in older patients and endurance athletes, and it may be under-diagnosed or inadequately treated due to a lack of understanding. Passive deep flexion of the knee can exacerbate the pain associated with semimembranosus tendinopathy.
To treat semimembranosus tendinopathy, conservative management strategies such as relative rest, ice, and non-steroidal anti-inflammatory drugs (NSAIDs) are typically recommended. However, there is a lack of consensus on the most effective conservative management approach due to limited scientific evidence. In some cases, surgical intervention may be necessary.
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The semimembranosus is tested by flexing the leg at the knee joint against resistance
The semimembranosus is a large, flat, membranous muscle that is one of four posterior thigh muscles, three of which are hamstring muscles. It is wider, flatter, and deeper than the other hamstring muscle, the semitendinosus. The semimembranosus is the most medial of the hamstring muscles and lies deep to the semitendinosus. It is a hip extensor and a knee flexor/intrarotator.
To test the semimembranosus, the patient is positioned in the supine position with the hip and knee extended. One hand is placed over the anterior thigh to maintain full extension throughout the movement. The hip is then flexed until firm muscular resistance to further motion is felt. To emphasise the stretch of the semimembranosus, a little external rotation of the hip and adduction can be added.
The semimembranosus can also be tested by positioning the patient in the prone position with a pillow or bolster under the ankles. A needle is inserted perpendicular to the muscle surface directly into the TrP taut band identified by a flat palpation technique. The leg is then rotated laterally to isolate the distal part of the semimembranosus muscle.
The semimembranosus can also be tested by having the patient perform active knee extension until myoclonus is observed in the hamstring. The patient should be positioned in the supine position with the hip at 90 degrees and the knee extended. The knee is then extended through its full range of motion while the hip is maintained at 90 degrees.
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Frequently asked questions
The semimembranosus is one of four posterior thigh muscles that are responsible for extending the hip. It is a large muscle that spans the full length of the thigh, from the hip to the knee. It is also one of the three muscles collectively referred to as the hamstring muscles.
The semimembranosus muscle flexes and medially rotates the leg at the knee and extends the thigh at the hip joint. It is also a knee flexor and intrarotator.
The semimembranosus muscle originates from the ischial tuberosity.
To stretch the semimembranosus muscle, sit on a firm table or chair with your legs hanging off the edge. Place a ball under your right hamstring, where you feel it is tight. Slowly lift your foot, extending your knee a few times. Then, move the ball onto the next tender spot along the muscle.
