Total knee arthroplasty (TKA) is the preferred intervention to treat end-stage knee osteoarthritis (OA). Over 600,000 TKA procedures were performed in 2011, and that number is expected to increase to 3.5 million per year by 2030. Although TKA is generally considered successful at relieving the pain associated with knee OA and restoring function, suboptimal outcomes including difficulty with stair climbing do occur. Patients with TKA tend to navigate stairs slower than healthy adults and only about ¾ of patients are satisfied with their pain relief when climbing stairs. Therefore, the goal of my dissertation is to determine the factors that are associated with stair climbing ability before and after TKA, and how we can improve a patient’s likelihood of achieving better postoperative stair climbing function, which will ultimately result in a better quality of life.

Stair climbing performance is often measured by the stair climbing test (SCT), where patients who ascend and descend a full flight of stairs faster are considered to have better function. Since stair climbing is a more demanding activity than level ground walking, the SCT gives a better estimation of a knee pathology patient’s maximal function capabilities. However, how climbing stairs faster alters stair climbing biomechanics, how stair climbing biomechanics are related to clinical function scores, and the effect that surgical technique has on postoperative stair climbing ability are currently unknown.

3D motion capture technology and an instrumented 3-step staircase were used to describe stair climbing biomechanics. SCT time, knee extension strength, and self-reported function were also collected in the knee pathology population. During the TKA procedure, the surgeon used a custom surgical navigation and stability device to measure knee stability and passive kinematics before and after insertion of the prosthesis.

To define the relationship between stair climbing biomechanics and stair climbing speed, a convenience sample of 30 healthy individuals performed stair ascent and descent trials at 3 different self-selected speeds. The findings suggest that in healthy subjects, the hip is the greatest contributor when modulating stair climbing speed, while additional knee contributions do not appear necessary to increase speed.

In the OA and TKA populations, SCT time was not associated with stair climbing knee biomechanics;​ consequently, patients with faster SCT times do not necessarily have different biomechanics compared to patients with a slower SCT times. There was an association between trunk lean and perceived instability suggesting that increasing trunk lean may be an adaptation used to combat instability.

Intraoperative measures of anterior-posterior (AP) passive kinematics and AP laxity were not associated with stair climbing biomechanics before or after TKA. Nevertheless, AP laxity was a significant contributor in a linear regression model exploring the best model to predict SCT time six months after surgery, suggesting that the use of quantitative measurements may improve the probability of good functional outcomes. Being able to predict postoperative stair climbing ability may have implications regarding the decision to have TKA, the best time to undergo TKA, help set functional expectations after surgery, and guide patient specific rehabilitation.

The biomechanics of stair climbing in OA and TKA populations compared to heathy populations are well defined, yet, to our knowledge, no study to date has investigated the effects of TKA on stair climbing biomechanics longitudinally. Preliminary findings suggest that sagittal plane knee, hip and trunk biomechanics are unchanged after TKA. These results indicate that prosthesis design advancement is still needed in order to achieve more normal biomechanics after surgery. The results also have implications for rehabilitation and the need to address movement patterns and neuromuscular control. Clinicians may want to focus decreasing the amount of trunk lean in patients with TKA to promote more normal kinematic and kinetic patterns.

The results of this dissertation provide an important step towards understanding the clinical and biomechanical factors that affect stair climbing ability in knee OA and TKA populations. The methodology presented in these studies lays the groundwork for future research to determine the necessary steps in achieving good stair climbing function after TKA, and, more importantly, improve overall quality of life in populations with knee pathology.