Background: Hip osteoarthritis (OA) is a musculoskeletal condition that makes walking difficult due to pain induced by weight-bearing activity. Treadmills that support body weight reduce the load on the lower limbs, and those equipped with a lower-body positive pressure (LBPP) device, developed as a new method for unweighting, significantly reduce pain in patients with knee OA. However, the effects of unweighting on gait kinematics remain unclear in patients with hip OA. Therefore, we investigated the effects of unweighting on kinematics in patients with hip OA during walking on a treadmill equipped with an LBPP device.
Methods: Fifteen women with hip OA and fifteen age-matched female controls wore a three-dimensional motion analysis system and walked at a comfortable speed on the LBPP treadmill. Data regarding hip pain using a numeric rating scale under three different unweighting conditions (100%, 75%, and 50% bodyweight) were collected. Sagittal plane lower-limb kinematics under each condition were calculated and compared.
Results: In the hip OA group, numerical rating scores at the unweighted condition were significantly decreased compared to the 100% bodyweight condition, and sagittal kinematics in the hip and knee joints significantly decreased compared to the healthy controls. In both groups, unweighting significantly decreased the peak hip flexion angle and increased the peak ankle plantarflexion angle during walking.
Conclusions: Although unweighting by LBPP decreased pain in the hip OA group, gait kinematics did not improve despite less load on the hip joint. Therefore, clinicians should consider the benefits of pain reduction, rather than improved gait, when considering LBPP treadmill for patients with hip OA.