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Similarities in early flexion kinematics suggest that the anterior cam-post is supporting normal-like anterior-posterior motion in the BCS subjects. Likewise, lateral femoral rollback and external rotation of the femur in later flexion provides evidence for appropriate substitution of the PCL via the posterior cam-post. Being discrete in nature, the dual cam-post mechanism does not lend itself to adequate substitution of the cruciate ligaments in mid-flexion during which anterior cruciate ligament tension is decreasing and PCL tension is increasing in the normal knee.

Clinic records of 37 manipulations in 767 consecutive primary total knee arthroplasties (TKAs) were analyzed to identify any predictors of manipulation outcome. Factors studied were sex, age, body mass index, tibiofemoral alignment, surgical history, smoking history, range of motion before TKA and manipulation, intraoperative lateral release, implant design and manufacturer, and manipulation interval. Measures of outcome were gains in extension and flexion from manipulation and range of motion at 1-year follow-up. Patients gained an average of 4 degrees of extension and 22 degrees of flexion after manipulation, resulting in average extension of 1 degree and average flexion of 105 degrees at 1-year follow-up. Restored flexion was similar to that measured preoperatively. Manipulation was most effective in patients manipulated within 8 weeks, with full extension and <90 degrees of flexion prior to manipulation, and those receiving a lateral release during arthroplasty. Potential for benefit from manipulation appears to be reduced in patients with large flexion contractures but with adequate flexion. Patients with flexion contractures regained only approximately 80% of the extension they lacked before manipulation. Only 12 of 18 patients (67%) with flexion contractures regained full extension. Manipulation is successful at regaining flexion and restoring function for patients of all levels of flexion deficiency. At least 90 degrees of flexion was regained in 20 of 23 patients (87%) who lacked it at manipulation.

The purpose of this study was to characterize the prevalence of taper damage in modular TKA components. 198 modular components were revised after 3.9±4.2y (range: 0.0–17.5y). Modular components were evaluated for fretting corrosion using a semi-quantitative 4-point scoring system. Flexural rigidity, stem diameter, alloy coupling, patient weight, age and implantation time were assessed as predictors of fretting corrosion damage. Mild-to-severe fretting corrosion (score≥2) was observed in 94/101 of the tapers on the modular femoral components and 90/97 of the modular tibial components. Mixed alloy pairs (p=0.03), taper design (p<0.001), and component type (p=0.02) were associated with taper corrosion. The results from this study supported the hypothesis that there is taper corrosion in TKA. However the clinical implications of fretting and corrosion in TKA remain unclear.

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