Sciatica can cause knee pain in some cases, as the sciatic nerve runs through the lower back and down the back of the legs, and can be compressed by a herniated disc or other spine issues which can cause pain, numbness, or weakness in the legs and knee. This is called referred pain, which means the pain originates from a different source but is felt in another area. The knee pain experienced with sciatica is usually a dull ache and might be accompanied by numbness or tingling in the knee.