Often martial arts injuries occur at the knee and these frequently occur as a result of training ignoring the structure of the knee. The knee complex prefers to function strictly as a hinge, with flexion and extension being the primary motions, although a lesser amount of medial-lateral rotation is permissible. Knee damage is not an integral part of martial arts training and need not occur if your martial arts training is sympathetic to the structure of the knee.
If your training practice works against, rather than with, the knee complex structure, debilitating damage can occur over time. Full force kicks into thin air or poor alignment of the supporting leg in round kicks can cause hyperextension at the knee of the kicking leg or excessive rotation of the supporting leg respectively, compromising joint integrity. Put simply, these practices are likely to mess your knee up. Training that works within the parameters of normal knee function allows the joint to survive and thrive. Its common sense really.
Preventing further knee damage
One of the ladies who trains with us has a tough time with her knees. They have never been right from as far back as I can remember. The original knee damage was a result of being a dance student at university. Certain movements, exercises, and techniques cause her knee trouble. Recently she had been complaining about how she was experiencing knee injury pain when posting on one foot and firing strikes from that position. This seemed wrong to me, as the posting action itself should not cause her knees any trouble at all, assuming she was lined up to the target correctly.
Following our recent conversation we agreed to spend a little time analysing her technique. I noticed that after posting on her lead leg she was turning on the ball of her foot. As all of her weight was on the lead leg this turning action at the foot was transferring to the knee and causing pain in the injured joint. It was little wonder she struggling with movement and footwork.
Comparing this observed movement with my own I realised that I tend to make and extra adjustment movement before striking. Initially I shift my weight onto the lead leg but then adjust its position to align with the target by making a tiny step with first the back and then the front foot. These small adjustments not only line you up but act like the larger switch kick movement to prime (or load) the leg muscles plyometrically, thereby adding power to the strike thrown. One explanation and demonstration later combined with practice and things improved!
We spent a lot of time getting to grips with these movements in Primal but they are very similar, if not identical, to the minute adjustment actions good Muay Thai fighters use. These actions ensure a fighter is light-footed while allowing him/her to adjust to their position in relation to the target without causing excessive rotational force on the knee joint.
(Knee) pain without gain
No-one wants to exacerbate an existing martial arts injury and by listening to your body while getting someone to analyse your movement you can avoid this outcome. The moral of the story is to listen to your body and act on what you hear! Rather than fight through discomfort, work something out to avoid further damage to knee joint. In this case there is no gain with pain!