The muscles of the thigh

Quadriceps and hamstrings: the four heads that extend the knee, the three muscles that flex it and extend the hip.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Quadriceps: what is it?
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Rectus femoris and vastus lateralis, medialis and intermedius, joining on the patella and tibia.
It is the only knee extensor.
A sprinter feels a sharp pain at the back of the thigh mid-stride. Which group is probably injured?
- The hamstrings
- The quadriceps
- The adductors
- The sartorius
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The hamstrings
They brake the leg eccentrically at the end of the swing; the biceps femoris is the most often injured.
Rectus femoris: what is it?
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The only quadriceps head crossing the hip: it extends the knee and flexes the hip.
It crosses two joints.
Why is the rectus femoris less effective at extending the knee when sitting bent forward?
- It does not cross the knee
- The flexed hip already shortens it
- It is a knee flexor
- The flexed hip already stretches it
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The flexed hip already shortens it
A two-joint muscle shortened at both ends loses force: active insufficiency.