## 3 Results
For the Knee Society Score (KKS), the highest median value was in the aseptic loosening group (84.0, IQR 81.0-88.0) and the lowest median value was in the malpositioning group (56.5, IQR 49.4-66.0). For the range of motion (ROM), the highest median value was in the periprosthetic fracture group (105.0\({}^{\circ}\), IQR 96.0-111.0\({}^{\circ}\)) and the lowest median value was in the infection group (88.5\({}^{\circ}\), IQR 77.5-98.0\({}^{\circ}\)). The [PERSON]'s test (with Bonferroni correction) was used to perform post hoc comparisons (see Supplementary Materials) and determine where the differences lie. For the OKS, the comparisons between the periprosthetic fracture group and the infection group (p.adj = 0.012) and between the aseptic loosening group and the infection group (p.adj \(<0.001\)) were significant. For the EQ-VAS, the comparisons between the periprosthetic fracture group and the infection group (p.adj \(<0.001\)) and between the instability group (p.adj \(<0.001\)) and the malpositioning group (p.adj \(=0.032\)) were significant. Moreover, the comparisons between the aseptic loosening group with the infection group (p.adj = 0.01) and with the instability group (p.adj = 0.005) were also significant. For the EQ-5D-5L, the comparisons between the infection group and the aseptic loosening group (p.adj \(<0.001\)) and between the instability group (p.adj \(<0.001\)) were significant. For the KKS, the comparisons between the aseptic loosening group and the infection group (p.adj \(<0.001\)) and between the instability group (p.adj \(=0.034\)) and the malpositioning group (p.adj \(<0.001\)) were significant. Moreover, the comparisons between the periprosthetic fracture group with the infection group (p.adj = 0.035), and with the malpositiong group (p.adj = 0.002) were also significant. For the ROM, the [PERSON]'s test showed that the comparisons between the infection group with the periprosthetic fracture group (p.unadj = 0.018), and with the aseptic loosening group \begin{table}
\begin{tabular}{c c c} \hline \hline
**Patients Feature** & \(\mathbf{X^{2}}_{\text{KW(4)}}\) & \(p\)**-Value** \\ \hline FU(months) & 3.42 & 0.49 \\ \hline AGE & 4.75 & 0.31 \\ \hline BMI & 1.18 & 0.88 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Demographic features comparison among the preoperative-cause-of-revision groups. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Outcome** & \(\mathbf{X^{2}}_{\text{KW(4)}}\) & \(p\)**-Value** \\ \hline OKS & 22.2 & 0.0002 ** \\ \hline EQ-VAS & 32.9 & \textless{}0.0001 ** \\ \hline EQ-5D & 51.8 & \textless{}0.0001 ** \\ \hline KSS & 47.5 & \textless{}0.0001 ** \\ \hline ROM & 12.0 & 0.0167 * \\ \hline \hline \end{tabular}  
* significance level \(p<0.05\). ** significance level \(p<0.005\).  
\end{table} 
Table 3: Postoperative functional outcomes comparison among the preoperative-cause-of-revision groups. (p.unadj = 0.0016) were significant only at the level of the incorrect \(p\)-value. All other comparisons were not significant (see Supplementary Materials). The group with preoperative diagnosis of aseptic loosening included 25 patients; in this group, according to AORI classification: 0 patients had bone defects classified as AORI I, 6 patients had bone defects classified as AORI IIA, 12 patients had bone defects classified as AORI IIB, and 7 patients had bone defects classified as AORI III. The group with preoperative diagnosis of malpositioning included 24 patients; in this group, according to AORI classification: 16 patients had bone defects classified as AORI I, 8 patients had bone defects classified as AORI IIA, 0 patients had bone defects classified as AORI IIB, and 0 patients had bone defects classified as AORI III. The group with preoperative diagnosis of infection included 20 patients; in this group, according to AORI classification: 0 patients had bone defects classified as AORI I, 7 patients had bone defects classified as AORI IIA, 8 patients had bone defects classified as AORI IIB, and 5 patients had bone defects classified as AORI III.