Introduction and Aims: Late degeneration of the ACL injured knee may be in part due to repeat injury, but also due to aberrant kinematics altering the wear pattern at the chondral surface. The aim of this study was to use tibio-femoral contact mapping by MRI to examine kinematic changes due to chronic ACL deficiency.

Method: Twenty subjects with a recent unilateral ACL deficiency (mean 13 months since injury) and 23 subjects with a chronic ACL deficiency (mean 18 years since injury) were recruited. Passive ligament laxity was quantified using a KT1000® device. Subjects performed a closed-chain leg press, relaxed and against a 15 kg weight. MRI recorded the tibio-femoral contact position at 15-degree intervals from zero to 90 degrees of knee flexion. Tibio-femoral contact points were measured at each position. Damage to the knee was recorded for all subjects by MRI, and at arthroscopy.

Results: The tibio-femoral contact pattern of the ACL injured knee was different from the healthy contralateral knee (p = 0.001). The contact pattern of the recently injured knees was different to the chronic ACL deficient knees (p = 0.034). In the recently injured knees the lateral compartment of the knee showed a posterior pattern of femoral contact, and in the chronic ACL deficient knees the medial compartment showed a posterior femoral contact pattern, particularly at zero and 15 degrees of knee flexion (p < 0.01), with the femur two millimetres (mean, SD 3.2mm) posterior on the tibial plateau. There was no difference in passive laxity between the recent and chronic injured knees (side-to-side difference: 5.8mm±2.4 for the recently injured knees, and 4.6±2.8mm for the chronic ACL-deficient knees). Nine of 20 recently injured knees had associated joint damage: three medial and three lateral meniscal tears, two with medial femoral condyle and two with patello-femoral damage. Eleven of 23 chronic ACL deficient subjects had associated joint damage: 15 medial and 16 lateral meniscus tears, 16 with medial and 12 with lateral compartment chondral damage. Greater kinematic changes in the chronic ACL deficient knees were associated with more severe chondral damage in the medial compartment.

Conclusion: ACL injury shifts the axis of rotation of the knee medially. In chronic ACL deficiency the tibio-femoral contact pattern is altered in the medial compartment, where it is associated with joint damage. These findings describe the relationship between aberrant kinematics and wear in the ACL deficient knee.

Introduction and Aims: The chronic ACL deficient knee has a natural history of degeneration and deterioration in function. It is unclear whether reconstruction will prevent this sequela. Reconstruction using hamstrings graft techniques have not been yet been evaluated over the long term. This prospective study used MRI to measure tibio-femoral contact patterns pre-and post-reconstruction.

Method: There were 20 subjects with an ACL injury of three years standing. The diagnosis was clinical and confirmed at surgery. They performed a closed chain leg-press, relaxed and against a 150N load. MRI recorded the tibio-femoral contact position at 15-degree intervals from zero to 90 degrees of knee flexion. Passive laxity was measured with a KT1000, and knee outcomes recorded using a Cincinnati score. Testing was performed pre-operatively, at 12 weeks and two years post-operatively.

Results: KT1000 showed a side-to-side difference of 5.1 ± 2.6mm pre-operatively, 2.5 ± 2.2mm at 12 weeks and 2.1 ± 2.3 at two years. Using Cincinnati ratings five rated ‘fair’, five rated ‘good’, and eight rated ‘excellent’. Tibio-femoral contact patterns loaded were not different loaded or unloaded, but medial and lateral compartments of the knee were significantly different (p< 0.001), demonstrating the longitudinal rotation of the knee during flexion, for healthy and injured knees. Pre-operatively the tibio-femoral contact patterns for the ACL injured knee were different to the healthy knee (p=0.014). At 12 weeks post-operatively the tibio-femoral contact patterns were not significantly different (p=0.117), and at two years the contact patterns were restored to those of the healthy knee (p=0.909). However, there were changes to the lateral compartment contact pattern that affected both the ACL injured, reconstructed and healthy knees over the two-year time period. In the healthy knees and also the reconstructed knees the lateral compartment showed less tibio-femoral rollback at two years.

Conclusion: The knee reconstruction restored the tibio-femoral contact pattern to that of the healthy contralateral knee, but both the healthy and reconstructed knees showed changes over time independent of surgery. One or more of the listed authors are receiving or have received benefits or support from a recognised academic body for the pursuance of the study.

Introduction and aims: Osteoarthritis (OA) of the knee is a widespread problem, yet there is little known about the kinematics of the osteoarthritic knee, and nothing about the tibio-femoral contact pattern. This study aimed to describe the role of tibio-femoral interface events in articular surface wear and degenerative change.

Method: Fourteen subjects with symptomatic OA in one knee, and no pain or injury in the contralateral knee were recruited. The tibio-femoral contact pattern was recorded for both knees, while performing a supine leg-press from 0 to 90 degrees flexion against a 150N load. Severity of osteoarthritis was measured by Kellgren Lawrence grade, bone mineral density (BMD) using Dual Energy X-ray Absorptiometry close to the subchondral bone, diagnostic MRI, and joint damage recorded at knee arthroplasty. Pain and disability was recorded using a WOMAC questionnaire.

Results: Severity of OA in the knees ranged from grade two to four (mode=4) in the symptomatic knee, and from zero to three (mode=0) in the contralateral knee. Contact in the lateral compartment of the knee was more anterior on the tibial plateau than healthy knees (p≤ 0.01), and this was associated with severity of OA (p≤ 0.01). Contact in the medial compartment was also more anterior on the tibial plateau, and this was associated with severity of OA. Abnormality in tibio-femoral contact patterns was associated with disability reported by the WOMAC score (r= 0.54). There was no significant difference in BMD between the OA and contralateral knees. However, the BMD was correlated with pain and physical function of the WOMAC score, that is, as function decreased, bone density increased in the arthritic compartment (r = 0.49 to 0.63; p≤ 0.01).

Conclusion: Severity of osteoarthritis was associated with loss of rollback normally coupled with flexion, especially in the lateral compartment. Consequently longitudinal rotation was lost. In severe osteoarthritis, ACL integrity did not affect the contact pattern. Kinematic abnormalities may explain loss of range of motion, and patterns of wear in osteoarthritic knees.

Introduction Late degeneration of the ACL injured knee may be in part due to repeat injury, but also due to aberrant kinematics altering the wear pattern at the chondral surface. The aim of this study was to use tibio-femoral contact mapping by MRI to examine kinematic changes due to chronic ACL deficiency.

Methods Twenty-three subjects with a history of chronic ACL deficiency (mean 18 years since injury) performed a closed chain leg press, relaxed and against a 15 kilogram weight. MRI recorded the tibio-femoral contact position at 15° intervals from 0° to 90° of knee flexion. Intra-articular pathology was assessed for all subjects by MRI, and at arthroscopy for 10 subjects.

Results The tibio-femoral contact pattern of the ACL injured knee differed from the healthy contralateral knee (p=0.003). This difference was greatest in the medial compartment, particularly at 0° and 15° of knee flexion (p< 0.01), with the femur two millimetres (mean, SD 3.2 mm) posterior on the tibial plateau. Damage to the chondral surface was seen in the medial compartment in 16 subjects and lateral compartment in 12; medial meniscus damage was present in 16 subjects and lateral meniscus in 15. Chondral surface damage correlated with the difference in the tibio-femoral contact pattern between the healthy and injured knee in the medial compartment of the knee. Joint damage was not related significantly to time since injury, or Cincinnati knee score. Joint damage was related to level of sports participation, but probably indicates that as the joint failed, subjects curtailed their activity.

Conclusions The kinematic consequences of chronic ACL injury may in part be responsible for the pattern of degenerative change, especially in the medial compartment of the knee.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Introduction In-vivo study by MRI has contributed to the understanding of knee kinematics for prosthetic design and the impact of knee pathology. The aim of this study was to compare the characteristics of knee motion exhibited by the tibio-femoral contact footprint and centre of the femoral posterior condyles over the tibial plateau during the flexion arc.

Methods Twelve subjects (five males, ages 19 to 42 years) with a unilateral anterior cruciate ligament (ACL) injury performed a supine leg press against a 15 kg load. Sagittal MR images recorded the motion from 0° to 90° flexion of both knees. The tibio-femoral contact points and the position of the posterior condylar centres were measured against the reference of the tibial plateau, at 15° intervals, for both the healthy knee and the ACL injured knee.

Results The tibio-femoral contact points in the healthy knee began anteriorly on the tibial plateau, and progressed posteriorly during the flexion arc. From 0° to 30° the footprints of the medial and lateral compartments are almost parallel. Onward from 30°, the lateral condyle moved further posteriorly than the medial condyle. In the ACL injured knee the footprint was more posterior on the tibial plateau, particularly on the lateral condyle, suggesting the axis of rotation of the knee had shifted medially due to ACL loss. The posterior condylar centres in the healthy knee were positioned over the centre of the tibial plateau in knee extension. The medial condylar centre remained central during the flexion arc, whereas the lateral condylar centre moved back over the tibial plateau. In the ACL injured knee the posterior condylar centres were more posterior than the healthy knees from 0° to 15°, but from 30° to 90° are not significantly different to the healthy knee. The difference in the position of the posterior condylar centres in the ACL injured knee between 0° and 15° indicates the effect of ACL deficiency on the governing axis of the knee in extension, as evidenced clinically by the pivot shift.

Conclusions The tibio-femoral contact patterns describe events at the articular surface whereas posterior condylar centres reflect the movement of the axis of rotation at the knee; two characteristics of knee kinematics. The altered action of the ACL injured knee at the tibio-femoral interface has implications for the development of wear changes in the chronic ACL injured knee.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Aim: A method of analysing the kinematics of the knee has been developed using magnetic resonance imaging (MRI) at regular intervals of knee motion. This method was tested for reliability and applied to normal and injured knees.

Method: MRI scans were used to study knees of 11 healthy subjects and knees of eight patients ACL with injuries. Scans were taken at 15 degrees intervals from 0 degrees to 90 degrees flexion, using a positioning jig to enable scanning with the knees either loaded or unloaded. The tibiofemoral contact points were mapped for each knee position, loaded and unloaded, in the medial and lateral compartments. The data were analysed for repeatability by interclass correlation and compared with known data.

Results: High reliability was achieved using T1 weighted fast spin echo images, scanned into Adobe Photoshop, or gradient echo sequences, downloaded as Dicom files and analysed using Osiris. Gradient echo sequences have advantages in efficiency without loss of reliability. Analysis of ACL-deficient knees confirmed aberrant contact-point behaviour compared with the non-injured side. The results showed that right and left normal knees and loaded and unloaded uninjured knees did not demonstrate significant differences but that medial and lateral condyles did demonstrate significant differences reflecting the longitudinal rotation of the knee during flexion.

Conclusions: The technique of MR imaging of the knee for kinematic analysis has been demonstrated to be robust and reliable. This technique may be applied to assessments of the effect of knee injury on the biomechanics of the knee or the results of surgical and physiotherapy interventions.