Knee pain and front split

Everytime i do front split, the moment when my front leg lock/extend my knee starts to hurt and i can barely hold the position. I know that the knee is connective tissue between the calve muscle and the quad and the hip, so i stretch these muscles before i do the split, but the pain is still there. I would appreciate any advices and tips how to get rid of this.

Can you describe the pain better? Specific location, motions that aggravate, positions where it is absent or ameliorated, nature of the pain, etc.

A lot of people have difficulty describe pain. Please put in some effort. You will be better for even having made the description. Try to discriminate between pain and related sensations like the typical discomfort of stretching and exercise.