Thank you for your query No, Icthyosis vulgaris does not cause knee pain. The stress of pregnancy and weight could cause it. Gradual Weight reduction would go a long way to help alleviate your symptoms. Have you checked your thyroid function or lipid profile recently? May explain the weight gain If the pain is severe I would recommend consulting your doctor before starting any exercise regimen. make sure you have good supportive shoes to avoid further strain or injury to your knee. Low impact exercises like walking, swimming and elliptical will help you lose weight without much strain to your knee hope this helps. wish you good health