Google search of "tightness and clicking in knee" and found this:
What are the possible causes of clicking and catching of the knee?
• Cavitation. Sometimes the noise you hear is due to tiny air bubbles inside the joint fluid, which build up with changes in the joint pressure. When the bubbles burst, this is called cavitation. Cavitation is typically something that is not worrisome – as long as it is unaccompanied by other symptoms (like swelling or severe pain).
• Ligaments and tendons. Another possible cause of clicking and catching of the knee is when the ligaments and tendons catch as they go over a bony lump – and pop as they snap back into place. Like cavitation, this is also not considered to be a serious problem if unaccompanied by other symptoms.
• Soft tissue. Clicking (and popping) may also be caused by the catching on soft tissue or scar tissue within the knee. Most of the time, these noises are natural and do not necessarily mean that you’ll develop other issues (including arthritis).
• Meniscus tear. If you feel some pain as the clicking/popping occurs, it could be a sign of a meniscus tear, which means there is a small piece of loose cartilage caught in the knee. Treatment for a torn meniscus commonly includes rest, pain relievers and physical therapy. Less commonly, surgery may be required.
• Osteoarthritis. If you’re experiencing painful and persistent clicking/popping, it could indicate osteoarthritis, in which the smooth cartilage has worn down and the bones cause friction when they rub against one another.
• Patellofemoral Pain Syndrome. Another common problem that results in the clicking and catching of the knee is roughness on the undersurface of the patella, which is also referred to as “runner’s knee.” With this syndrome, you may often feel the popping, grinding, clicking or crunching more than you can hear it.
