1, the extensor muscle strength and flexor muscle strength is severely imbalanced, that is, the flexor muscle strength is too small.
The analysis with biomechanics should consider the force of the link comprehensively. If the effect of gravity is not considered, the conclusion that the knee is hyperextended because the flexors are stronger than the extensors is undoubtedly correct, but on earth gravity must be considered, and gravity is an important cause of knee flexion during walking, which does not require flexor contraction, so this explanation is wrong. Well, this denial is correct. Knee hyperextension is the effect of gravity, not the cause of low flexor muscle strength.
2. Hypertonicity of the knee extensor muscles.
Increased tension of the quadriceps is not the direct cause of knee hyperextension, that is, decreasing the tension of the quadriceps does not improve knee hyperextension. Lower extremity knee spasm is certainly one of the causes of knee hyperextension, and this cannot be denied. The moderator is right to say that it is not a “direct cause”, because high knee extension tension only straightens the knee joint and does not “hyperextend” it, but if you insist on looking at the problem this way, then you can deny all the causes of knee hyperextension.
3. weakness of the knee extensor muscles.
I don’t know why the moderators don’t comment on this? Agree? It is indeed possible to have weak knee extension muscles and take knee hyperextension in order to lock the knee joint. But if you use the owner’s theory of the second point above, this is not a direct cause? How does knee extensor weakness not directly lead to knee hyperextension?
4, triceps hypertonicity/i.e. foot drop, passive inability to cross neutral position.
For example, most patients with knee hyperextension can passively cross the neutral position when lying down, but when walking the knee hyperextension is afraid to cross the neutral position, the point of doing so is to prevent falls. The moderator’s comment is incorrect! It is because the ankle dorsiflexion is limited and the ankle joint cannot reach the neutral position in the standing position or in the supporting phase and the foot must land on the full foot, which is the reason for the knee hyperextension according to the closed chain movement. This is the main factor for knee hyperextension in most hemiplegic patients! The owner’s opinion is correct.
5. It may be related to hip control.
Yes, sometimes knee hyperextension is related to hip control. According to the closed chain theory, the ROM of each joint in the lower extremity in the standing and supporting phase is related, not only the above-mentioned ankle joint is related, but also the hip joint is indeed related, such as patients with high hip flexion tension, hip flexion, increased lumbar lordosis, and forward shift of the center of gravity, bringing about knee hyperextension.
6. Weak quadriceps muscle strength is also a cause of knee hyperextension.
Article 3 says weakness of knee extensor muscles and this one is tautological repetition. I don’t think so. Not much comment.
7, weakness of one knee joint
If this is the cause, then the hemiplegic patient should have weakness of the knee extensor muscle on the affected side and hyperextension on the healthy side, which I have not seen in my ignorance. I have not heard of it either. There is no reason for the explanation of the brother yuan7807 upstairs: a patient with one leg amputation must have knee hyperextension in the other leg? Our knee is self-locking in the extended position, and walking single leg support phase load is about 4 times the weight, which is not a problem at all. The problem you describe is basically a problem on the hyperextended side itself that causes hyperextension, such as triceps spasm, etc.
8, flexor spasm or contracture causing knee hyperextension; are patients with clubfoot and knee hyperextension concomitant?
Yes, the authors are right, triceps spasm or Achilles tendon contracture is indeed one of the causes of knee hyperextension. The moderator’s challenge is unjustified: we are only saying that it is one of the causes, not that it is inevitable. If you look at a patient with clubfoot, is there any gait other than knee hyperextension and hip flexion? Moreover, patients with horseshoe foot have a long period of compensations, while hemiplegic patients with triceps spasm or Achilles tendon contracture have established a trunk-neutral body control pattern, and the most direct form of compensation to maintain this pattern is knee hyperextension.
9. Knee hyperextension is used to compensate for knee collapse gait; what is knee collapse gait?
Knee collapse gait will only result in quadriceps contraction protection and will not result in knee hyperextension.
10, Support phase knee extension spasm; there is no muscle group that spasms only in one phase and is normal in other phases.
The authors mean knee extension spasm after standing, right? Of course, there is no different muscle tone in the walking phase, but it is still very common to see no significant muscle tone in the prone position and a significant increase in muscle tone once standing for support. The explanation is as in point 2.
11, the line of gravity falls in front of the center of the knee joint when the trunk is flexed forward, prompting the knee joint to extend posteriorly to maintain balance.
This is a good point, knee hyperextension basic two reasons: weak knee muscles and trunk forward flexion. Oh, raise a bar: this is not the direct cause either. The direct cause would be the laxity of the joint capsule, tendons and ligaments on the back side of the knee, right? As long as the joint structure is strong, the knee joint will not be hyperextended, right? Haha, I’m just kidding, don’t mind. This is definitely true!