Abstract
Aims: Kinematics of the arthritic knee joint is to date not very well understood, yet this is a significant parameter affecting the results of knee arthroplasties; we studied the axial rotation of the tibia during knee flexion in osteoarthritic knees in order to understand better the kinematics of the arthritic joint.
Methods: Tibial rotation and the screw home mechanism were studied in 55 consecutive patients (31 females and 24 males) with diagnosed knee OA. The assessment was performed by consultant orthopaedic surgeons using the trackers and the software of a navigation system, prior to any soft tissue release. The Student t-test was used for the statistical analysis.
Results: We identified 3 different patterns of tibial rotation during knee flexion.
-
26 knees had normal tibial rotation pattern with the tibia rotating internally during knee flexion (mean rotation: 15.5°).
-
In 22 knees (40%) the tibia was rotating internally and then externally as the flexion was progressing (mean rotation: 6.7°).
-
In 7 joints (13%) a reverse tibial rotation was recorded, the tibia was rotating externally in all flexion increments (mean rotation: 2.2°).
We also recorded that most of the tibial rotation occurs in the first 0–30° of flexion (70%) p< 0.001.
Conclusion: The screw home mechanism and the normal tibial rotation upon knee flexion were absent or distorted in the majority of osteoarthritic knees. We found three distinctive patterns of the tibial rotation (normal, erratic and reversed) during knee flexion.
Correspondence should be addressed to Mr T Wilton, c/o BOA, BASK at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE, England.
