## 4 Discussion
only KAM2 of the involved side was found to be significantly smaller compared to healthy controls (approximately 33%) and the non-involved side (25%), as was found by [PERSON] et al [36]. A significantly lower KAM2 indicates a medial-to-lateral shift in the knee load [14; 16] and might lead to increased degenerative cartilage wear. The load in the non-involved hip joint was slightly higher compared to the involved hip joint, as was found in preoperative hip OA patients [13; 14]. Although these differences were not significant, they might be due to a learned gait pattern to reduce the load on the OA side. The significant differences compared to the healthy control group confirmed the extra load on the non-involved side. The question of whether leg alignment and femoral parameters explain the pathological joint adduction moments in unilateral hip OA patients has not been answered before. The clinical leg parameters FO, HKA, NSA, and FMA showed a significant correlation (or a trend toward significance) with the knee adduction moments. The positive correlation between the KAM and the FO means that a larger FO implicated a larger KAM, and vice versa. The negative correlation of the KAM with the NSA, the HKA, and the FMA means that a varus leg (a smaller HKA) led to higher knee adduction moments. A larger NSA, and therefore a more valgus leg, was associated with a decreased KAM. Indeed, varus malalignment has been known to be a predictor for the peak knee adduction moments in patients with knee OA [22], and leg malalignment is thought to be one of the main risk factors contributing to the progression of knee OA [5]. [PERSON] et al. [17] showed that the hip and pelvic anatomy had an influence on the occurrence of medial and lateral knee OA. A decreased NSA, which leads to a more varus leg, was associated with medial knee OA. These results were supported by the present results, as a smaller NSA increased the knee adduction moments during gait. The clinical leg parameters explained 61% of the variance in KAM1 and 50% of the variance of KAM2. For the hip adduction moments, no correlations were found with the clinical leg parameters. In the previous literature, the effect of the FO on gait was discussed. A lower FO led to an asymmetrical gait pattern with a reduction in the knee RoM [37]. [PERSON] et al. [38] showed that with a smaller FO, the abductor muscle force must increase to preserve a normal gait pattern. These results agree with [PERSON] et al. [37], who reported that a reduction in the offset was related to a reduction in the abductor muscle strength (moment-generating capacity) of the operated hip. As was found in clinical studies [39; 40], the gait pattern is more influenced by a decrease than by an increase in the FO. The effect of the NSA on the hip moments has recently been shown in patients after a THR [41]. In this research, we also studied whether the clinical leg parameters in combination with the gait kinematics were better associated with the pathological hip and knee adduction moments. Till now, only the gait kinematics have been related to the pathological adduction moments in unilateral hip OA patients: [PERSON] et al. [14] found a significantly more outward rotation of the foot in their patients, where the FPA, together with the knee RoM, explained 39% of the KAM2 alterations. In the present study, no correlation between KAM2 and the FPA was found. The severity of OA might explain the lack of correlation between KAM2 and the FPA. [PERSON] et al. [42] found that only for asymptomatic and mild-to-moderate knee OA patients, the FPA was associated with alterations in the knee adduction moments. In the present study, all patients were symptomatic and severely affected. In the present study, a significant reduced knee RoM during gait was found in the involved limb compared to the non-involved limb and healthy controls.