Police, firefighters and paramedics were scrambled to Salters Road, just outside Dalkeith, shortly after 4.30pm on Sunday following a crash just before 4pm.
At least one of the cars involved, a white Seat Leon, is thought to have hit the boundary wall of Dalkeith Country Park.
The second car, a dark-coloured Toyota Celica, was nearby.
Police confirmed that the driver of the Seat was taken to hospital with pelvic and abdomen injuries but has since been dischaged.
The driver of the Seat remains in hospital but is due to be released.
“It looks like a pretty nasty smash,” said an eyewitness. “They’d cut the roof off one of the cars.”
Traffic was backed-up along Salters Road as emergency services blocked the carriageway.
The road was closed for over 6 hours following the incident.
Two teenage bike thieves were taken to hospital last month after ploughing into a police van on the same stretch of road.
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