Radiographic Identification of the Primary Medial Knee Structures

Background: Radiographic landmarks for medial knee attachment sites during anatomic repairs or reconstructions are unknown. If identified, they could assist in the preoperative evaluation of structure location and allow for postoperative assessment of reconstruction tunnel placement. Methods: Radiopaque markers were implanted into the femoral and tibial attachments of the superficial medial collateral ligament and the femoral attachments of the posterior oblique and medial patellofemoral ligaments of eleven fresh-frozen, nonpaired cadaveric knee specimens. Both anteroposterior and lateral radiographs were made. Structures were assessed within quadrants formed by the intersection of reference lines projected on the lateral radiographs. Quantitative measurements were performed by three independent examiners. Intraobserver reproducibility and interobserver reliability were determined with use of intraclass correlation coefficients. Results: The overall intraclass correlation coefficients for intraobserver reproducibility and interobserver reliability were 0.996 and 0.994, respectively. On the anteroposterior radiographs, the attachment sites of the superficial medial collateral ligament, posterior oblique ligament, and medial patellofemoral ligament were 30.5 +/- 2.4mm, 34.8 +/- 2.7 mm, and 42.3 +/- 2.1 mm from the femoral joint line, respectively. On the lateral femoral radiographs, the attachment of the superficial medial collateral ligament was 6.0 +/- 0.8 mm from the medial epicondyle and was located in the anterodistal quadrant. The attachment of the posterior oblique ligament was 7.7 +/- 1.9 mm from the gastrocnemius tubercle and was located in the posterodistal quadrant. The attachment of the medial patellofemoral ligament was 8.9 +/- 2.0 mm from the adductor tubercle and was located in the anteroproximal quadrant. On the lateral tibial radiographs, the proximal and distal tibial attachments of the superficial medial collateral ligament were 15.9 +/- 5.2 and 66.1 +/- 3.6 mm distal to the tibial inclination, respectively. Conclusions: The attachment locations of the main medial knee structures can be qualitatively and quantitatively correlated to osseous landmarks and projected radiographic lines, with close agreement among examiners. Clinical Relevance: The present study identifies medial knee structure attachment sites with use of radiographic landmarks and thus allows for reliable preoperative and postoperative assessments of surgical repairs and reconstructions of the main medial knee structures.