jointline

Jointline refers to the boundary formed by the articulating surfaces of adjacent bones in a synovial joint. It is both an anatomical concept and a radiologic reference point used to describe joint alignment and the status of the joint space. In clinical practice, the joint line can be approximated on imaging by drawing a line along the margins of the articular surfaces on standard radiographs or MRI; deviations from the expected position may indicate injury, laxity, or degenerative change.

In radiology and orthopedics, evaluating the joint line helps assess conditions such as osteoarthritis, malalignment, and post-traumatic injury. In the knee, surgeons frequently discuss restoring or preserving the native joint line during total knee arthroplasty or osteotomy, because improper joint line position can alter ligament balance and knee kinematics.

Outside medicine, the term joint line is rarely used; when encountered, it is usually in a figurative sense to describe a seam or boundary in manufactured assemblies. The concept remains most central in medical contexts, particularly in imaging interpretation and surgical planning related to synovial joints. See also joint space, osteoarthritis, and knee arthroplasty as related topics.