Abstract
Background
The cruciate ligaments are important structures for biomechanical stability of the knee. For total knee arthroplasty (TKA), understanding of the exact function of the (PCL) and anterior (ACL) cruciate ligament during walking is important in the light of recent designs of bicruciate TKAs. However, studies evaluating in vivo function of the PCL during daily activities such as walking are scarce. We aimed to assess the role of the PCL during gait by measuring kinematics and kinetics of individuals with PCL deficiency and compare them with individuals with ACL deficiency and healthy young adults.
Methods
Individuals with unilateral PCL deficiency (PCLD; n=9), unilateral ACL deficiency (n=10) and healthy young adults performed (n=10) 10 walk trials (5 for each leg) in which they walked over a force platform. Motion analysis (Vicon Motion Capture System) was used to calculate joint angles and internal moments around the knee, hip and ankle in the sagittal plane. Joint angles and moments of the injured knee (in PCLD and ACLD) or left knee (in HYA) were compared between groups at weight acceptance, mid-stance and push-off phases (see Fig. 1). Clinical assessment included passive knee laxity (Kneelax) for anterior (in 20–30° knee flexion) and posterior tibia translation (in 70–90° knee flexion) and Lysholm questionnaires.
Results
Lysholm scores were significantly lower in PCLD and ACLD individuals compared to HYA (p's ≤ .001). PCLD subjects had more passive anterior (p = .001) and posterior tibia translation (p = .041) compared to HYA, but no significant differences were found in both directions between ACLD and HYA (p's > .10). During gait, knee angles at weight acceptance, late stance and around toe-off were not significantly different between the PCLD and HYA, and between ACLD and HYA (all p's > .06). However, the knee extension moment during mid-stance was significantly lower in the PCLD group when compared to the HYA group (p = .001; Fig. 2). Interestingly, the knee moment in the PCLD group remained positive (i.e. extension moment) throughout the stance phase, whereas HYA and ACLD groups created a substantial flexion moment around the knee at this instant. We did not observe any significant differences in hip and ankle joint angles and moments between groups.
Discussion
We observed a difference in gait pattern in individuals with PCL deficiency compared to HYA, that was confined to an absence of knee flexion moments during the mid-stance phase. We hypothesize that this difference reflects a compensation strategy employed by individuals with PCL deficiency to avoid external knee (hyper)extension moments. Gait adaptations related to PCL deficiency might also have implications for design of total knee prosthesis and calls for careful evaluation of gait patterns after TKA with a specific focus on the role of the PCL.
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