Original may be seen here:
http://www.tjq.hk/forum.php?mod=viewthread&tid=42
陈瑜老师讲习练太极拳时如何预防膝盖痛
Chen Yu Laoshi speaking about how to prevent knee pain during the
practice of taijiquan.
许多太极拳友曾经对我讲过，自己在开始习练太极拳时，有时会隐隐约约地感觉到膝盖痛，并随着练拳次数的增加，这种痛觉会不断加重。那么造成膝盖痛的原因是什么呢？如何预防呢？在此以陈式太极拳为例，我来谈谈自己的看法，希望能对大家有所帮助。
Many taijiquan friends have said to me, when I start to practice taijiquan, sometimes I become faintly aware of knee pain. And, indeed, it increases the longer I practice. This type of pain is likely to continually get more serious. So, what is the reason for the emergence of knee pain? How does one prevent it? Taking Chen-style taijiquan as an example, I'll speak a bit on my own views, and hope that it might be of some help to everyone.
首先造成膝盖痛的原因主要有以下几点：
First, the reasons for the emergence of knee pain are mainly in the following few points:
原因一：各种运动都离不开肌肉、骨骼和关节的活动。而陈式太极拳对全身各部位的协调要求更为细致。如:中正不偏，含胸拔背，沉肩坠肘，尾闾中正等等。同时还对裆、胯、膝也提出了明确的要求：屈膝松胯。即：强调在习练每一招势时都要屈膝、圆裆、开胯。陈式太极拳运动量相应较大，加之屈膝、圆裆、开胯，所以腿部要支撑全身活动的重量，而以膝关节负担的重量更为明显，因此膝盖必须有力、灵活。动步出腿时，则始终轮流以一足支撑重心，一足提起蹬出。太极拳的动作又是慢速度进行的，因此膝关节的担负比其他拳种要大得多。如果不得要领，必然会造成膝盖痛。
Reason 1: Of all the various movements, none can be separated from the activity of the muscles, the bones, and the joints. Moreover, the coordination of all the parts of the whole body is even more intricate. Like: being erect without leaning, han xiong ba bei, sink the shoulders drop the elbows, tailbone erect, etc. At the same time, as to the crotch, the kua, and the knees, this brings up clear-cut requirements: bend the knees, relax the kua. That is, it must be emphasized that when practicing any of the postures, one must bend the knees, round the crotch, open the kua. The amount of movement in Chen-style taijiquan is relatively large. Add to that bending the knees, rounding the crotch, and opening the kua. So, the legs must support the weight of the activity of the whole body. Moreover, the weight borne by the knee joints is even more obvious. Because of this, the knee must be strong and flexible. When the legs step out, from beginning to end, each in turn, one leg in turn supports the center of gravity, and one leg is raised and steps out. Taijiquan movements are also executed slowly. Therefore, what the knee joints bear is greater than other forms of boxing. If one fails to grasp the main points, the emergence of knee pain is inevitable.
原因二：有的拳友错误地把放松误认为就是一味地向下蹲，这时劲变为了抽劲。重心便落在了膝关节上，为了站稳，势必会身体前倾，膝盖向前跪，结果膝盖超过脚尖，这样便加大了膝关节的重量。长期以往便会出现膝盖痛的感觉。
Reason 2: Some boxing friends mistakenly consider fang song to invariably be sitting down. At this time, jin is changed to chou jin. The weight then drops to the knee joints. In order to stand steady, the posture must be the body leaning forward, the knees kneeling forward, resulting in the knees extending past the toes. This way easily increases the weight on the knee joints. In the long term then, knee pain is likely to appear.
原因三：在陈式太极拳中有许多转脚、转身的动作。我经常发现有的拳友只转脚，而膝盖并不随之转动，那么这时力就会压在膝盖上。这也是导致膝盖痛的原因
Reason 3: In Chen-style taijiquan there are many movements involving turning the feet and turning the body. I often discovered that some boxing friends only turn the feet, and the knees do not follow the movement, so then the force is likely to put pressure on the knees. This is also a reason leading to knee pain.
原因四：许多拳友误认为五指抓地，脚心空就是用自己的脚趾尖抠住地，这样重心就会落在前脚掌上，从而无形当中便加大了对膝关节的压力。致使身体失去了灵活性。这样也很容易造成膝盖的疼痛。
Reason 4: Many boxing friends mistakenly think that the toes grasping the ground and the arch (掌心) empty means that they dig into the ground with their toes. This causes the weight to fall to the front of the sole and thus invisibly facilitating an increase of pressure on the knee joint. This causes the body to lose its agility. This is another way that it's easy to create knee pain.
习练太极拳本应起到养身的作用，但因不得要领却起到了相反的作用。要想预防膝盖痛，我认为要注意以下几点：
Practicing taijiquan should have the effect of nourishing the body, but failing to grasp the main points has the opposite effect.
If you want to prevent knee pain, I think you should pay attention to the following points:
1、对于初学者来说，架式要放高一些，这样可以减轻对膝关节的压力。
1. As for beginning students, the form must be done a bit higher, thus lightening the pressure on the knee joint.
2、迈步时要先提起大腿，使力聚膝关节来带动脚跟提起。做踢腿或独立动作时，膝盖上提的高度要与胯平。
2. When stepping you must first lift the thigh, such that the force gathers in the knees joints to provide impetus to the raising of the heel. When kicking with the leg or standing on one leg, the height of the lifted knee should be level with the kua.
3、放松时气下沉，手放远，跨根同时沉下去。定势时，膝关节要有微向里合之意，同时配合胯根撑开撑圆，把裆劲合住，裆要圆
3. During fang song, the qi sinks, the hands are placed at a distance, the kua gen sinks simultaneously. When in a stable stance (ding shi), the knees must have the intent of closing inward slightly. At the same time, coordinate the kua gen supporting its openness and roundness. Close the crotch energy. The crotch must be round.
4、前足弓出踏实时，膝盖不要过脚尖，以免失去平衡，从而加大膝关节的承受力；也不宜膝尖与小腿成垂直线，以免影响下一动作的灵活性。只需略向强伸便可。
When in stepping out to the front in a bow step, the knees must not extend beyond the toes, in order to avoid losing balance, thereby increasing the tolerance of the knees; it is also not advisable for the point of the knee and the lower leg to form a vertical line, in order to avoid affecting the flexibility of the next move. It only needs a little stretching and that's acceptable.
5、转脚时，同时膝盖也要随之转动，这样膝盖不会感到太大的压力，因此膝盖不会出现痛的感觉。
When turning the feet, the knees must also follow in the turning movement, this way the knee is not likely to feel too great a pressure. Because of this, it is not likely that pain would appear in the knees.
6、在练拳时，重心要放在脚心和脚后跟的中间位置上，并用脚趾头肚轻微抓住地。
6. When practicing, the center of gravity must be positioned in the middle between the arch and the heel of the foot, and use the toes to lightly grip the ground.
古人云：“功到自然成”，不要误解为盲目的练，求数量；而应是要按照严格的要求，循序渐进，反复练习，发现并纠正错误，才能真正起到强身健体的作用。
The ancients said: “Skill will naturally lead to success”. Don't take this to mean blind practice, seeking quantity. Rather it should be seen as depending on strict requirements, proceeding gradually step by step, discovering and correcting one's mistakes. Only in this way can can one's practice truly rise to the purpose of strengthening and invigorating the body.
以上是我在多年的习练和教授陈式太极拳过程中，针对膝盖痛这一现象自己的一些见解，愿拿出来与大家共同讨论，仅供参考。
These are my personal views regarding knee pain developed over the years in the process of practicing and teaching Chen-style taijiquan. I present them as reference for everyone to discuss.
[translated by John Warriner taijitu@cox.net]