Introduction: The factors causing chronic instability, a common sequela of ankle inversion sprains are unclear, despite wide investigation. However, few studies have examined potential factors during the injuring movement. We therefore measured the ability of dancers to control ankle movement during quiet stance and after a perturbation into inversion in a group with chronic instability (N=16) and healthy controls (N=26).

Methods: Control of ankle movement was determined by the magnitude of lateral oscillation at the ankle, measured by a 3SPACE Fastrak. The oscillation was measured during single leg stance (baseline oscillation) for two foot positions, flat and demi-pointe. In both positions, the time taken to return to the baseline oscillation after an inversion perturbation (perturbation time) of 15° for the flat foot and 7.5° for the demi-pointe position was also determined.

Results: The baseline oscillation was significantly smaller (P< 0.005) on the demi-pointe for the sprained group (2.5 ± 0.5 mm) than for controls (4.0 ± 2.3 mm). In addition, the perturbation time for the flat foot was significantly longer (P< 0.05) for the sprained group (2.2 ± 0.4 sec) than for controls (1.8 ± 0.5 sec). However, there was a higher (P< 0.05) failure rate among the sprained group for both the perturbation test with the foot flat and for baseline oscillation on the demi-pointe than among the controls.

Conclusions: Our findings demonstrate altered sensorimotor control in chronically unstable ankles. Those sprainers who successfully completed the tasks “braced” the ankle, allowing a small range of oscillation. The increased perturbation time in the sprained group may reflect a deficit in either detection of inversion movements, peroneal muscle response, or both.

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.