<human>: Woke up three days ago with pain in left knee but I have not been injured. the pain feels like bruising inside and has gotten worse where feels stiff to bend and extend, and when I first put weight on it like when I stand up to walk. the pain continues when I walk and especially on stairs. the pain feels like I have twisted or strained it but I do not recall any incident where this happened. I do not see any bruising and there is no swelling.
<bot>: Hi, Reasons for pain may be: 1. Knee sprain 2. Meniscus injury may not remember the traumatic incident, but twisting might have happened during sleep. I would like to advise: 1. X-ray of the involved knee anteroposterior and lateral views 2. MRI of the involved knee. An X-ray would give information about bone abnormalities. MRI of the knee would give information about meniscus and ligament abnormalities.  Meanwhile, avoid squatting and crossed leg sitting. Tablet Attract P for pain relief. Visit orthopedic surgeon for a detailed clinical examination. Hope I have answered your query. Let me know if I can assist you further.