A method to improve the calculation of knee configuration angles in clinical and sport biomechanics

Abstract

Knee injuries are quite common in sports activities. Biomechanical analyses seek to improve understanding of the mechanisms that produce injury, and to find ways to reduce the incidence of injury. The calculation of knee torques and knee configurations requires the establishment of three-dimensional reference frames attached to the thigh and to the shank. Most clinical biomechanics researchers use the methods proposed by Kadaba et al. (1990) and by Davis and al. (1991). The calculation of the resultant knee joint torques and of the knee joint deformation is hampered by an important methodological problem. The problem is that usually no distinction is made between knee configuration angles and knee deformation angles. The primary purpose of this study was to look for a solution to this problem. Ten male subjects and four female subjects were recruited to participate in the investigation. The subjects performed three types of tests. In the first type the subject performed slow flexions and slow extensions of the right knee in unloaded conditions. In the second type of test they performed a series of 4 straight runs. In the third type of test they performed a series of 4 trials in which they ran forward and executed a cutting maneuver to the left. The trials of types 2 and 3 were given in random order. Three-dimensional leg segment orientations and joint angles were calculated from the landmark location data. v The results support the measurement of angles in unloaded trials to provide adjustments for the raw ab/adduction angles of loaded activities. On the other hand, such an approach is not currently possible for the internal/external rotation angles due to the large intra-subject variability of the internal/external rotation angles in the unloaded trials. The adjusted ab/adduction angles generally reached less extreme values than the unadjusted ones. The standard Kadaba/Davis methods do not include such adjustments. Therefore, the ab/adduction angles calculated with those methods are inflated. In summary, the present project demonstrated a new method for improving the calculation of knee configuration angles. These results can be applied in both clinical and sport biomechanics in ways that will ultimately be of benefit in the future study and treatment of knee injuries.