My mother is 4 months pregnant and is 34 and 3 times already her knee has had times where she cannot walk but the the next day she can what is this?

Let me explain: There are two general types of locked knees. The locked knee can either be caused by a mechanical block to knee motion, or a locked knee can be caused by pain that is too severe to allow knee motion. When a locked knee is caused by a mechanical block to motion, there is something that is physically being caught within the mechanism of the knee. Patients can have locked from pain.