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| the joint of the leg that allows for movement between the femur and tibia and is protected by the patella |
| a large, triangular muscle covering the joint of the shoulder, the action of which raises the arm away from the side of the body |
retractor re·trac·tor (rĭ-trāk'tər)
n.
A surgical instrument used to hold back organs or the edges of an incision.
A muscle, such as a flexor, that retracts an organ or a part.