Table 2. The interpretation of those deviations from the mean knee function represented by each PC illustrated in Fig 2.

Component	Interpretation
PC1- Overall Magnitude:	A larger positive score (i.e. similar to younger group) indicated a change in frontal plane alignment towards a less abducted/more adducted position and a more externally rotated and anteriorly positioned tibia through to terminal stance. A large score also indicates a greater relative magnitude in adduction and external rotation in mid-stance.
PC2-Flexion and secondary joint motion and coupling:	A larger negative score (i.e. similar to middle-age group) indicates a more flexed knee in mid-stance and greater relative knee adduction in early versus later stance as well as a more externally rotated and anteriorly positioned tibia through-out stance.
PC3- Relative early and late stance magnitude:	A larger negative score (i.e. similar to younger group) indicated a smaller difference in the relative magnitude of the knee flexion and knee ab/adduction in early stance and late stance. In addition, a larger negative score corresponded with a more internally rotated and posteriorly positioned tibia relative to the femur.
PC5-Early flexion and secondary motion coupling:	A larger positive score (i.e. similar to middle-age group) indicates a more extended/less flexed knee at heel-strike and early mid-stance, greater knee adduction/less abduction in early mid-stance vs later mid-stance, and an internally rotated but more anteriorly positioned tibia in mid-stance through toe-off.
PC6- Detailed features of the movement:	This component describes the inflexions within curve including knee flexion and tibial external rotation at heel strike and local maxima in early stance for both the knee adduction and int/external tibia rotation.