There are two muscle groups of the thigh that act to move the knee joint.
Learn Muscle Anatomy: Knee Joint Group
Posted on 1/14/14 by Courtney Smith
As I sit here, typing, I've got my legs crossed. My chiropractor would probably throw something at my head if he knew. Oh well. Is YOLO still a thing? Because YOLO.
Where my legs are crossed (at the knees) there are several muscles of the lower limbs in play. And of course there are—do you know how many anatomical structures it takes to move your knee? Probably more than you think.
The muscles of the knee joint are incredibly important. They move when you do—when you walk, run, dance, stretch your legs, or make any action you can think of that involves bending the knees.
There are two muscle groups that act on the knee joint: the quadriceps femoris and the posterior compartment of the proximal leg. In addition to these groups are the plantaris, articulus genu, semiteninosus, semimembranosus, and popliteus.
Bursae are fluid-filled sacs that can be found anywhere skin rubs over bone, and where a muscle, ligament, or tendon glides directly over the periosteum (outer surface) of a bone. The synovial fluid in the bursae linings provides lubrication, enabling freedom of movement between contiguous connective tissue surfaces.
The bursae found in the knee include the superficial prepatellar, superficial and deep infrapatellar, medial and lateral gastrocnemius, suprapatellar, and quite a few more.
So, I'm still sitting with one knee crossed over the other and somewhere my chiropractor just became flushed with rage and has no idea why. If I stand, however, I will be straightening, or extending, my knees.
Extension increases the angle between body parts. Flexion decreases the angle. Stand up for a moment and keep your legs perfectly straight—this is extension.