Contributions of proximal and distal moments to axial tibial rotation during walking and running

Abstract

The purpose of this study was to determine the cause and effect relationship between tibial internal rotation and pronation of the foot during walking and heel–toe running. This would allow predictions of orthotic effectiveness in reducing knee pain related to excessive internal tibial rotation. Kinematic and force plate data were collected from twenty subjects performing ten running and ten walking trials across a force plate. Using a least-squares algorithm, attitude matrices for each segment in each frame were obtained and the angular velocity vector of the tibia was calculated. The intersegmental moment at the ankle was calculated from ground reaction force and kinematic data, and the power flow from foot to tibia associated with axial tibial rotation was calculated. In walking, all subjects exhibited a clear power flow from tibia to foot during most of the stance phase, indicating that the foot was following the body. This suggests that the use of foot orthoses to reduce knee pain associated with tibial rotation during walking will not be successful. During running, power flow was also mainly proximal to distal, but there were brief periods of opposite power flow. There was more variability between subjects during running, with five subjects having large distal to proximal power flow peaks. These observations may explain and support previous work that has found variable clinical effects of orthoses between patients.

Introduction

It has been suggested that certain knee injuries are caused by excessive internal tibial rotation. (Clement et al., 1981; James and Jones, 1990; Tiberio, 1987) or a delayed external tibial rotation (McClay and Manal, 1997). As external rotation is linked to knee extension, excessive internal rotation during the stance phase of walking or running may delay the natural external rotation as the knee begins to extend. This has the potential to increase torsional joint stresses at the knee or within the tibia and in turn cause knee injury. For further comprehension of this potential injury mechanism, it is essential to understand where the cause of tibial rotation is located.

Tibial internal rotation is coupled to eversion of the foot through the ankle joint complex. The anatomy of the ankle joint complex can be modelled as two separate hinge joints, at the talocrural joint and one at the subtalar joint. The subtalar joint between talus and calcaneus is approximately 45° inclined from the horizontal. As the calcaneus everts, this mechanism should transfer into a similar amount of tibial internal rotation (McClay and Manal, 1997; van den Bogert et al., 1994). Experimental work has verified this coupling between the internal rotation of the tibia and the eversion of the foot. Nigg et al. (1993) found that the coupling of the eversion of the foot to the internal rotation of the tibia had an extremely high correlation of r²=0.991 for running. If tibial rotation is linked to knee injuries and is coupled to eversion of the foot this may imply that controlling eversion with foot orthoses could reduce tibial rotation and thus knee pain. The assumption in this is that foot eversion causes internal tibial rotation. However, if tibial rotation originates proximally to the tibia, and the foot merely follows the tibia, controlling eversion may increase the resistance against tibial rotation and cause more stress on the tibia and knee. One could use an analogy between the tibia and the driveshaft in an automobile. If the brakes are used when the engine is powering the vehicle, stress in the driveshaft will increase. If the brakes are used when the engine is slowing down the vehicle, for instance when going down a steep downhill slope, stress in the driveshaft will decrease.

Clinically, orthotics are a common treatment for patients with knee pain due to running injuries. Orthoses used in conjunction with conventional therapies such as rest, medication, and physiotherapy are more effective than conventional treatments alone (Kilmartin and Wallace, 1994). Yet, there is evidence in the literature to suggest that eversion may not always cause the internal rotation of the tibia. Studies of orthotic effectiveness on controlling the lower limb have found varying results on tibial rotations and negligible effects on knee kinematics (Kilmartin and Wallace, 1994). The effect of orthoses on knee range of motion has been found to be related to the type of activity being performed (Eng and Pierrynowski, 1994) and the effect of orthoses on tibial rotation shows large intersubject variability (Cornwall and McPoil, 1995). Lafortune et al. (1994) found that changes in tibial internal rotation due to orthotic intervention were not matched with changes in knee internal rotation thus implying compensation at the hip joint.

These conflicting clinical and biomechanical conclusions about orthotic effectiveness and the widespread use of orthoses suggest further questions. Research is needed to examine whether eversion causes tibial rotation in walking and running or if tibial rotation is caused proximally for some patients during all or some parts of the support phase of the locomotion and foot eversion is a result of this. In the latter case, orthotic therapies may not be effective. It is the purpose of this study to determine the cause and effect relationship between tibial internal/external rotation and forces acting on the foot during walking and heel–toe running in the normal population.