MSK - Posterior Thigh Muscles Flashcards
What are the three muscles that form the hamstrings?
- Biceps Femoris
- Semitendinosus (most superficial)
- Semimebranosus
What is the origin of biceps femoris?
- Long head = Ischial Tuberosity
- Short head = Linea aspera of the femur
Where does biceps femoris insert?
Heads converge to form a tendon that attaches at the head of the fibula
What is the arterial supply of biceps femoris?
Deep femoral artery and perforating arteries
What are the actions of biceps femoris?
- Flexion of the leg at the knee
- Lateral rotation of the knee when flexed
- Long head = extension of the leg at the hip
What is the origin of semitendinosus?
Ischial tuberosity
Where does semitendinosus insert?
Posteriomedial surface of the tibia
What is the innervation of semitendinosus?
Tibial part of the sciatic nerve (L5-S2)
What is the arterial supply of semitendinosus?
Inferior gluteal artery and perforating arteries
What are the actions of semitendinosus?
- Flexion of the leg at the knee
- Extension of the leg at the hip
- Some medial rotation
What is the innervation of biceps femoris?
- Long head = tibial part of the sciatic nerve (L5-S2)
- Short head = fibular part of the sciatic nerve (L5-S2)
What is the origin of semimembranosus?
Ischial tuberosity (but is superior to other muscles)
Where does semimembranosus insert?
Medial tibial condyle
What is the innervation of semimembranosus?
Tibial part of the sciatic nerve (L5-S2)
What is the arterial supply of semimembranosus?
- Profunda femoris
- Gluteal arteries
What are the actions of semimembranosus?
- Flexion of the leg at the knee
- Extension of the thigh at the hip
- Medial rotation of the leg at both the knee and hip joints
Describe a hamstring strain. When are these most likely to occur?
- Excessive stretching/tearing of the muscle fibres
- Seen in athletes involved in running/kicking sports
What can happen as a result of a hamstring strain?
Muscle damage can rupture the surrounding blood vessels which causes a haematoma that is contained in the fascia lata to form
What is an avulsion fracture? What happens with an avulsion fracture of the ischial tuberosity?
- The breaking away of a small part of a bone from its main body
- Hamstrings tear off a piece of the ischial tuberosity usually during an activity that requires rapid contraction/relaxation of the muscles e.g. football
