- Type I is nonbony ankylosis of the joint, with the fossa and condyle clearly seen but with scattered callus.
- Type II is lateral bony ankylosis of the joint, with bony fusion on the lateral side of the joint. The medially displaced condyle, residual disc, and fossa form a pseudarthrosis.
- Type III is complete bony ankylosis of the entire joint with a radiolucent line inside the fusion area but no recognizable condyle and fossa.
- Type IV is extensive bony ankylosis, with complete disappearance of the joint and with no radiolucent line.
