Purpose: The proximal tibiofibular joint (PTFJ) is a rather unknown articulation. There is little understanding of its anatomy, physiology, and functional role. The objectives of this research are to describe the normal kinematics of the PTFJ and its relation to the ankle and knee movements.
Methods: Fourteen knees of seven adult fresh frozen whole body cadavers were studied. The proximal tibiofibular joint and ligaments were identified, after which we sequentially sectioned the anterior proximal tibiofibular ligament (APTFL), the posterior proximal tibiofibular ligament (PPTFL), and the interosseous syndesmotic membrane. Models with intact and sectioned ligaments were compared, while the unloaded lower limb was manually mobilized in a pre-defined sequence of combined movements of knee, ankle, and proximal tibiofibular joints. The PTFJ spatial displacement was measured by analyzing the length of a distance vector between two 3D coordinate systems settled over the tibia and fibula.
Results: On the unaltered PTFJ, direct grasping of the head of the fibula with the hip in 45° of flexion and the knee in 90° of flexion was found to produce an average displacement of 7 mm. Knee movements caused the greatest spatial displacements, almost ten times the ones produced by ankle flexion/extension. Flexion/extension of the knee caused 1.8 times more displacement than single rotations with the knee flexed to 90°. It was found that the APTFL was an important stabilizer of the PTFJ when this joint is tensioned accommodating the movements of ankle extension and foot eversion. The APTFL was not a significant stabilizer of the PTFJ during direct manipulation of the fibular head when imprinting a manual force with posterior direction. The PPTFL was an important accommodator of ankle flexion, foot inversion and knee flexion. The interosseous syndesmotic membrane also proved to be a significant PTFJ stabilizer in rotational movements of the ankle and knee.
Conclusions: This is the first cadaver study to illustrate the PTFJ normal spatial displacement, thereby contributing to a deeper insight of this joint. The contribution of each ligament for PTFJ stability was described and, based on these findings; a new mechanism of injury was suggested. Surgeons can translate the results of this study into the clinical practice.
Keywords: 3D kinematics; Knee; Proximal tibiofibular joint; Tibiofibular instability.