Observed kneeling ability after total, unicompartmental and patellofemoral knee arthroplasty: perception versus reality

Kneeling is an important function of the knee, but little information is available on ability to kneel after different knee arthroplasty procedures. Previous work has asked patients about their kneeling ability; in this study it was objectively assessed. One hundred and twenty two patients - 38 having had total knee replacement (TKR), 53 unicompartmental knee replacement (UKR), 31 patello-femoral replacement (PFR) - were observed trying to kneel at 90 degrees on a chair, at 90 degrees on the floor, and at 120 degrees on the floor. Only 37% of patients thought they could kneel, whereas 81% were actually able to kneel ( p<0.001). Ability to kneel on the chair and on the floor at 90 degrees was significantly better than perceived ability for all prosthesis types ( p<0.001). Kneeling at 120 degrees showed no difference between perception and reality except for the PFR group ( p<0.05). In all positions, increased range of movement significantly improved kneeling ability ( p<0.001). Kneeling ability in men was significantly better than in women ( p<0.001). Patient-centred questionnaires do not accurately document kneeling ability after knee arthroplasty.