The lateral joint line opening: a radiographic indicative parameter for high grade varus knees

Abstract

Purpose It is usually assumed that the severity of varus osteoarthritis (OA) of the knee is correlated with the axis deviation of the limb. Despite this, there is currently no clear radiographic definition to define a so-called ‘high degree’ varus knee, which is characterized by a pronounced lateral ligamentous laxity. The purpose of this study was to radiographically determine if the lateral joint line opening (LJLO) is an indicative parameter when defining so-called high grade varus knees. Methods Two hundred forty Full length radiographs of patients with end-stage varus osteoarthritis who were scheduled for Total knee arthroplasty (TKA) were evaluated. The Hip-knee-ankle-angle (HKA-angle), Joint-line-convergence-angle (JLCA) and the lateral joint line opening were measured. The lateral joint line opening is the shortest distance between the lateral tibial plateau and the deepest point of the lateral femoral condyle. Linear regression models were used to investigate the relationships between the radiographic measurements. Results Hip-knee-angle-angle, joint-line-conversion-angle, and lateral joint line opening were all positively correlated (p < 0.001). An increase of 1 mm lateral joint line opening causes an increase of 0.6° joint-line-conversion-angle (p = 0.029) below a cut-off point of 4.7 mm. For lateral opening values beyond 4.7 mm, the gradient increased to 1.2 (p < 0.001). A lateral joint line opening of 4.7 mm corresponds to a hip-knee-ankle-angle of 6.0° (95% CI [5.5; 6.5]). Conclusion A lateral joint line opening of more than 5 mm in end-stage OA knees is indicative of increased lateral joint laxity. Those knees can be radiographically classified as so-called ‘high-grade’ varus knees. Level of evidence Therapeutic study, Level III.

Postoperative patient‐reported outcome measures after medial open‐wedge high tibial osteotomy was improved by decreased joint line convergence angle

“…Thus, the effect of ΔJLCA on long-term clinical outcomes requires further investigation. Finally, the JLCA is affected by the severity of osteoarthritis [4], target alignment [24,30] and intraoperative treatment of medial collateral ligament and pes anserinus [1], which may change the outcomes in different populations.…”

Is the Surface Anatomy of the Popliteal Crease Related to Lower Extremity Alignment or Knee Osseous Morphology? A Radiographic Study

“…The MPTA was defined as the angle of the medial side between the central axis of the tibia and the proximal tibial joint line, and the mLDFA was defined as the angle of the lateral side between the mechanical axis of the femur and the distal femoral joint line [14,18]. The JLCA was defined as the angle between the proximal tibial joint line and the distal femoral joint line, which is the positive value when the lateral was opened [19]. In addition, the angle between the transepicondylar axis (TEA) which connects both femoral epicondyles and the line connecting the most distal part of both femoral condyles in the Rosenberg view was measured to include radiologic parameters reflecting the mid-flexion state, and this was referred to as the mid-flexion condylar axis (MFCA)/TEA [20,21].…”