Many dancers have the ability to hyperextend their knees. The position of hyperextension feels straight to the dancer and breaking this alignment habit is hard to do. If you aren't familiar with the differences between hyperextension and straight, look at the pictures below. The same student appears in both pictures, in the one on the left she is standing in what she considers her natural stance (hyperextended), the picture on the right is where she constantly corrects to now that she knows the difference.
Pelvis tilted forward (left)
Pelvis more neutral (right)
Knees hyperextended (left)
Knees neutral (right)
Direction of force is back weighting the dancer (left)
Body is more upright and weight even (right)
Ankles plantar flexed (left)
Ankles more neutral (right)
What can't be seen from this view is that hyperextension will cause a reduction in turnout. To put the knee in the position of hyperextension the femur (thigh bone) and tibia (shin bone) will rotate inwards to "lock" the knee. Since most dance styles work in either parallel or turned out positions (but not turned in), this is counter productive.
The longer a dancer stands or works hyperextended the more difficult it will be to fix this problem. One reason is that the ligaments around the knee lengthen (or are naturally longer or have more slack to them) allowing the knee to bend backwards. The ligaments are part of the form closure of the knee, the inherent structure of support. Ligaments do not have the ability to tighten and return to their ideal length, even after the incorrect movement pattern is discontinued. Once the ligaments are lengthened, it is up to the dancer's muscular system to provide the support needed. This is called force closure (muscle tension / tone is an outside force). In order for muscle memory to kick in automatically and make finding neutral instead of hyperextension the new normal position, about 50,000 repetitions of finding that correct neutral must occur.
Hyperextension not only causes problems at the knee, but as evidenced in the picture above creates compensation both above and below. There are several other deviations which can occur to compensate for the hyperextension of the knees, all with different problems associated. Future blog posts will talk about the more common issues.
Here are some ways you can help your dancer to correct knee hyperextension:
For additional exercises focusing on weight distribution and alignment, check out Pre-Pointe a year long training guide.