Keyboard controlled knee. (QWOP mechanic)

Hiya guys. I am tring to create a human body with fully controllable joints. In the end it probably would look something like this: QWOP (I am also working in 2d)

I am using configurable joint with these settings:

• XMotion : Locked

• YMotion : Locked

• ZMotion : Locked

• Angular XMotion : Limited

• Angular YMotion : Locked

• Angular ZMotion : Locked Low angular XLimit : Limit -70 High angular XLimit : Limit 70

• Rotation Drive Mode : X & YZ

• Angular XDrive: Mode : Position

• Position Spring : 1000

• Position Damper : 200

• Maximum Force : 10

The script to control the movement is this:

     void Update()
 {
     targetAngle += Input.GetAxis("Vertical") * Time.deltaTime * rotateSpeed;
     Quaternion targetRotation = Quaternion.AngleAxis( targetAngle, Vector3.right );
     thisConfJoint.targetRotation = targetRotation;
 }

So THE PROBLEM is basically this - it doesn`t work the way I want to. The value of "targetAngle" can go higher or lower than the angle the leg can bend, and that causes the legs to jump around (if I hold down long enough for targetAngle go from +70 to -70 the wrong way) or a lag between movements (when targetAngle crosses the 70* line, and I have to wait for it to move back).

I am pretty new both to Unity and programming, and can`t seem to find a way to limit targetAngle`s value in the boundaries, or think of alternative solution for this. This is where I come to you guys - could anyone at least hint me the right direction to look at? :)