The muscles used to bend the knee, also known as knee flexion, include several muscles located in the posterior compartment of the thigh and leg. These muscles work together to allow you to flex your knee joint.
Knee Flexor Muscles
These muscles are collectively known as knee flexors.
- Hamstrings: This is a group of three muscles located on the back of the thigh:
- Biceps femoris
- Semitendinosus
- Semimembranosus
- Gracilis: This muscle is located on the inner thigh.
- Sartorius: The longest muscle in the human body, it runs diagonally across the front of the thigh.
- Gastrocnemius: This is one of the major calf muscles.
- Plantaris: A small muscle that runs along the back of the knee.
- Popliteus: This muscle is located at the back of the knee joint.
According to the reference, the hamstrings, gracilis, sartorius, gastrocnemius, plantaris, and popliteus muscles are responsible for flexing the knee joint. In addition to knee flexion, these muscles also play a role in the internal and external rotation of the knee.
| Muscle | Location | Primary Function |
|---|---|---|
| Hamstrings | Back of the thigh | Knee flexion, hip extension |
| Gracilis | Inner thigh | Knee flexion, hip adduction |
| Sartorius | Front of thigh (diagonal) | Knee flexion, hip flexion, abduction |
| Gastrocnemius | Calf | Knee flexion, ankle plantarflexion |
| Plantaris | Back of the knee | Knee flexion, ankle plantarflexion |
| Popliteus | Back of the knee joint | Knee flexion, internal rotation |
