paralysis of muscles of the following would make an individual unable to flex the knee?
478543
hamstring muscle group
892696
There are many different reasons why one would display hyperextension of the knee.  Some of it is genetic tendency to ligamentous laxity.  It can also occur as a compensation due to tightness in the achilles tendon or due to weakness of the quadriceps muscles.  Prolonged hyperextension can lead to failure of the ligaments of the knee in some cases.  The point here is that if you are having pain, time to see an orthopedist.  Orthotics, and/or physical therapy may be inorder to address whatever is driving the hyperextension.
186728
See;  Guillain-Barre.com, also check into  nih.gov (National Institute on Health), &  cdc.gov  .  Rapid onset weakness, sometimes paralyzing legs, arms, face, breathing muscles or, creating strage sensations in those areas.  It's not known what causes it.  I'm a Nurse though I no longer work....I've seen one case of it myself. I renewed my info on it at the above websites.
952414
Bag of frozen peas or something similar. If unable to weightbare or move limbs or extremities then see your GP.
175967
your muscle is shrinking because of lack of use or because of disease.
244015
Most people's legs aren't even, but if there's a significant issue, it can be attributed to several things. Polio could cause that, but you'd know if (s)he had contracted it somewhere down the line. It could just be some sort of genetic mutation.\n\nIf it poses a problem in his/her ability to function, see a doctor about surgery.\n\nYou should see a doctor regardless.
1181672
Extended position or Position of posterior flexion.
1056327
a pinched nerve perhaps?
320531
if you can't move them, it's probably because you don't have any muscles.  You need to work out.
1182544
It depends on the healing of the bones.  If the bones healed incorrectly, it is possible for the arm movement to be limited.  Another possibility is muscle atrophy .  This occurs when certain muscles haven't been used in a while.  Physical therapy and/or can correct this problem.\n\nIn either case, talk with a doctor who can give you specifics on the case in question.
316321
not sure but .... Spondylolisthesis can cause spasms that stiffen the back and tighten the hamstring\nmuscles
1058028
Be sure to talk to your doctor about this.  You may need some physical therapy to strengthen the knee.  If you are not happy with your doctor, seek another for a second opinion.  Life is short and you do not need to be slowed down by this disabling condition.
157743
There are no truly "double-jointed" people. Some people have tendons and ligaments that are not nearly as tight as others, and some have done enough stretching and bending to loosen their ligaments and tendons. The key is going slowly. Ligaments and tendons can separate, tear, and literally snap if you go too far too fast. Slow, smooth repeated motions that gradually extend your range of motion (like yoga) are probably best. You have some genetic limits that are related to how your own particular body is constructed. Someone else may have genetic limits that are greater or less than yours. You can however, in almost every case, improve your flexibility within the limits that your body type imposes.
172534
squats, leg lifts, basically tightening the muscles around the knee\nhttp://www.knee-surgery-info.net
148205
So bad that either:\n\n1. You will feel extreme pain if there is slight movement;\n\n2. You will not feel anything at all because you will be paralyzed.
416976
Probably the same reason a quadrapalegic feels disabled.
653891
in the knee there are four ligaments, the anterior cruciate, the posterior cruciate, the lateral collateral and the medial collateral ligaments.  injuries to these can include a partial sprain or a complete rupture.  Typically when injured there is a lot of swelling and considerable pain in the area.  the severity of the sprain is described using degrees.  1st degree would be a minor sprain, which would still allow for walking and use of the limb, but there would be some pain and a little bit of inflammation.  A second degree sprain can range from moderate pain and swelling to a more serious amount of pain, swelling and joint instability.  The person may or may not be able to walk, or would need crutches or a walking aid to get around.  Rehabilitation may include surgery or strengthening of the surounding musculature.  A third degree sprain is a rupture of that ligament.  this would result in instability of the joint and surgery would be required to safe guard the knee.