What may be causing tightness in knee area?

Patient: In 2010 I had knee surgery, a scope to fix a torn meniscus in my right knee, they said there was also an old ACL injury they saw, but seemed to be ok. Last week I woke with a tightness in my knee area, from back of hamstring to all around knee area. Movement is limited, not painfull but more of a tight feeling, however I cannot kneel on my knee with any weight as it causes severe pain. Any Advice or thought on what it may be?

Symptoms: Tightness in knee, limited movement, pain when placing weight on knee