Anatomy of the muscles that move the lower leg and knee joint

As for the muscles that move the knee joint, three of them lie on the front of the thigh; these are the largest muscles located on the thigh itself and their function is to extend the thigh. One of these three muscles seems to be doubled. It has two heads, one of which starts from the large process, and the other from the front of the thigh, and two ends. One of them is fleshy and attaches to the kneecap before turning into a tendon. The other extremity is membranous; it is adjacent to the inner end of the two ends of the thigh.

As for the remaining muscles, one of them is the one that we mentioned among the hip flexors, that is, the muscle growing from the crest of the iliac bone, the other begins from the external process on the thigh. These two muscles converge and connect; from them arises a single wide tendon that surrounds the kneecap and firmly fastens it to the underlying parts. Then it connects to the beginning of the lower leg and extends the knee, extending the lower leg.

The muscle that starts at the junction of the pubic bones is also used for extension. It descends, passing obliquely along the inside of the thigh, then connects to the upper part of the shin bone, which is not covered with meat, and extends the shin, deflecting it inward. Another muscle, as they say in some anatomy books, opposes the previous one on the outside. It starts from the thigh bone and extends obliquely on the outside until it comes to a place not covered with meat. There is no muscle more oblique than this muscle; she extends the lower leg with an outward deviation. When both muscles are extended, extension becomes complete.

As for the flexors of the leg, they belong to a narrow long muscle, starting from the bones of the ilium and pubis, close to the origin of the internal extensor muscle, and from the crest located in the middle of the ilium. Then it passes obliquely to the inner edge of the knee, then goes forward and ends at the protrusion on the meatless part of the knee, adjoining it. This muscle pulls the lower leg upward with the foot deviating towards the groin.

There are three more flexor muscles - internal, external and middle. The outer and middle muscles bend with an outward deviation, and the inner bend with an inward deviation.

The internal muscle begins at the base of the ischium, then it passes obliquely behind the thigh, reaches the meatless place on the lower leg on the inside and is adjacent to it. The color of this muscle is greenish.

Two other muscles also start from the base of the ischium, but only they deviate and connect to the meatless part of the leg on the outside.

In the knee joint there is a muscle, as if hidden in the bend of the knee. It performs the functions of that middle muscle.

Some believe that a part of the double extensor muscle, starting from the septum, sometimes participates incidentally in flexing the knee, and that from the junction of this muscle with the knee there arises a tendon that holds the “box” of the thigh and connects it with adjacent parts.