Knee pain from swimming the breaststroke is common. The tendon and ligaments on the inside of the knees get stressed, creating inflammation and pain. Adjustments to your kick may alleviate this problem by decreasing the pressure placed on your knee.
Decreasing the amount of internal rotation -- knees pointing toward each other -- will reduce stress to the insides of your knees. While bending your knees and hips into the breaststroke kick position, avoid turning your knees toward each other.
The second phase of this kick is abduction, which is moving your legs away from each other. According to Joanne Koury, author of "Aquatic Therapy Programming," adjusting this part of your kick by increasing the distance between your legs may decrease stress on your knees by decreasing hip rotation, while allowing for an effective kick.
Ankle eversion, pulling your little toes up toward the surface of the water, increases the medial stress on the knee. You may complete your adjustment by keeping your feet in a neutral position.
Whipping your lower legs quickly back together while increasing your propulsion also increases the force against your knees. Use a smooth, continuous motion rather than an abrupt, quick whip to minimize the stress to your inner knee.