INTRODUCTION

Accurate knowledge of knee joint kinematics following total knee arthroplasty (TKA) is critical for evaluating the functional performance of specific implant designs. Biplane fluoroscopy is currently the most accurate method for measuring 3D knee joint kinematics in vivo during daily activities such as walking. However, the relatively small imaging field of these systems has limited measurement of knee kinematics to only a portion of the gait cycle. We developed a mobile biplane X-ray (MoBiX) fluoroscopy system that enables concurrent tracking and imaging of the knee joint for multiple cycles of overground gait. The primary aim of the present study was to measure 6-degree-of-freedom (6-DOF) knee joint kinematics for one complete cycle of overground walking. A secondary aim was to quantify the position of the knee joint centre of rotation (COR) in the transverse plane during TKA gait.

ACL reconstruction is successful in restoring sagittal stability of the knee but has been less consistent in restoring rotational stability. Increasing coronal graft obliquity improves rotational constraint of the knee in cadaveric biomechanical models. The purpose of this study was to determine whether there is a correlation between coronal graft alignment and tibial rotation during straight line activities.

Seventy-four patients who had undergone ACL reconstruction using a transtibial technique were evaluated. They came from three distinct time periods during which the operating surgeon had deliberately changed the position of the femoral tunnel to progressively achieve a more oblique graft alignment in the coronal plane. Post-operative radiographs were analyzed for the coronal graft orientation and femoral and tibial tunnel positions. Tibial rotation was measured during level walking (n=74) and single-limb landing (n=42) tasks using a motion analysis system. Radiographic measurements of graft and tunnel orientation were correlated with rotational excursion of the knee recorded during these tasks. No correlations were found between knee rotational excursion and either the coronal tibial tunnel angle or the coronal graft angle during level walking. For the single-limb landing task, a significant negative correlation was observed between the coronal angle of the tibial tunnel and rotational excursion (r=−0.3, p=0.05) i.e. increasing tunnel obliquity was associated with decreasing rotational excursion. For the coronal angle of the ACL graft, the correlation was also negative, but was not significant (r=−0.24, p=0.12).

Increases in graft obliquity in the coronal plane were associated with reduced tibial rotational excursions during single limb landing. These findings support the notion that ACL graft orientation may play a role in rotational kinematics of the ACL reconstructed knee, particularly during higher impact activities.

Most people have not returned to their pre-injury level of sports participation 12 months following anterior cruciate ligament (ACL) reconstruction surgery. Twelve months may be too early to assess return to sport outcomes accurately. The purpose of this study was to evaluate the mid-term return to sport outcomes following ACL reconstruction surgery.

A self-report questionnaire was used to collect data from people at 2 to 7 years following ACL reconstruction surgery regarding pre-injury sports participation, post-operative sports participation and subjective knee function. The main inclusion criteria were participation in regular sports activity prior to surgery and the attendance of routine surgical follow up appointments.

A total of 314 people were included at a mean 39.6 ± 13.8 months following ACL reconstruction surgery. At follow up, 45% of people were playing sport at their pre-injury level and 29% were playing competitive sport. Of those playing competitive sport prior to injury, 46% were playing competitive sport at follow up. Ninety three percent of people had attempted sport at some time following their ACL reconstruction surgery. People who had not attempted their pre-injury level of sport by 12 months following surgery were just as likely to have returned to pre-injury level by 39 months after surgery as those who had played sport by 12 months (risk ratio, 95% CI = 1.1, 0.76–1.6).

Less than 50% of people had returned to either their pre-injury level of sport or competitive sport when surveyed at 2 to 7 years following ACL reconstruction surgery. Sporting activity at 12 months was not predictive of participation at 2 to 7 years, suggesting that people who return to sport within 12 months may not maintain their sports participation.

Increased knee flexion is seen as a primary goal in achieving a better functional outcome following TKR. However, the relationship between passive knee flexion and biomechanical outcome remains unclear. The aim of this study was to compare kinematic outcomes in TKR patients and controls during high flexion activities.

A three dimensional motion analysis system and two force platforms were used to collect kinematic and kinetic data from 40 patients who had undergone total knee replacement at least 12 months previously and 40 controls who were matched to the patients for age and gender. Participants completed the following activities six times: standing from a seated position, squatting, and lunging with each leg leading. Peak knee flexion angles and moments were compared between groups using t-tests and the correlations between passive knee flexion and functional knee flexion were calculated using ‘Pearson's r’.

For both squatting and lunging, peak knee flexion in the TKR group was significantly less than in the control group. There was no difference between the two groups for the sit to stand activity as peak flexion for this activity was primarily determined by the chair height.

Squat: control 124, TKR 91 (p<0.001) Lunge - op. forward: control 100, TKR 81 (p<0.001) Lunge - op. trail: control 106, TKR 84 (p<0.001) Sit to stand: control 87, TKR 85 (p=0.5)

Although there were significant correlations between functional and passive knee flexion in the TKR group for the squatting and lunging activities, the patients used only approximately 70 to 75% of their available flexion during these activities. As anticipated, there was only a weak correlation between passive and functional flexion for the sit to stand activity.

Percentage of passive flexion used: squat: 77%, lunge - op. forward: 68%, lunge - op. trail: 70% Sit to stand: 71%, Correlations: squat: 0.50, lunge - op. forward: 0.57, lunge - op. trail: 0.50, Sit to stand: 0.27

Normal sagittal knee kinematics during high flexion activities was not restored following TKR. Patients did not or were unable to use their available range of flexion to achieve a normal kinematic pattern. The cause of this important functional deficit remains to be established but may be amenable to targeted rehabilitation.

High tibial osteotomy (HTO) is an established treatment for medial compartment osteoarthritis of the knee; the aim being to achieve a somewhat valgus coronal alignment, thereby unloading the affected medial compartment. This study investigated knee kinematics and kinetics before and after HTO and compared them with matched control data.

A three dimensional motion analysis system and two force platforms were used to collect kinematic and kinetic data from eight patients with medial compartment knee osteoarthritis during walking preoperatively and 12 months following HTO (opening wedge). Nine control participants of similar age and the same sex were tested using the same protocol. Sagittal and coronal knee angles and moments were measured on both the operated and non-operated knees and compared between the two time points and between HTO participants and controls. In addition, preoperative and postoperative radiographic coronal plane alignments were compared in the HTO participants.

The point at which the mechanical axis passed through the knee joint was corrected from a preoperative mean of 10% tibial width from the medial tibial margin to 56% postoperatively. Stride length and walking speed both improved to essentially normal levels (1.57 m and 1.5 m/s) ostoperatively. In the coronal plane the mean peak adduction angle during stance reduced from 14.3° to 5.2° (control: 6.8°). Mean maximum adduction moments were similarly reduced to levels less than in control participants, in keeping with the aim of the surgical procedure: peak adduction moment 1: pre 3.8, post 2.7, control 3.6 peak adduction moment 2: pre 2.5, post 1.7 and control 2.6.

In the sagittal plane, both mean maximum flexion and extension during stance increased postoperatively—extension to greater than in control participants and flexion to almost control levels. The maximum external knee flexor moment during stance also increased to near normal postoperatively.

High tibial osteotomy appears to achieve the intended biomechanical effects in the coronal plane (reduced loading of the medial compartment during stance). At the same time there were improvements in sagittal plane kinematics and kinetics which may reflect a reduction in pain. The net effect was to reduce quadriceps demand.