Radiological evaluation of the proximal tibiofibular joint in knees with severe primary osteoarthritis

The proximal tibiofibular joint (PTFJ) can be considered to be the fourth compartment of knee joint. Although degenerative diseases of the knee joint may also have detrimental effects on the PTFJ until now, details of arthritic affection of PTFJ in the elderly who have severe femorotibial arthritis have not been described. Convenience samples of knees of elderly patients with Kellgren–Lawrence grade III–IV primary osteoarthritis were investigated further in order to determine the X-ray findings of PTFJ. Sixty knees in 34 patients with an average age of 71 years (61–86 years) were examined. Both knees were examined in 26 patients. On the radiographs, 23 joints were grade IV, 14 were grade III, and 23 were grade II. At most, only minor differences were seen between knees on the same patient in terms of lower extremity alignment, grade of TFJ degeneration, grade of PTFJ degeneration, and type of PTFJ. Interobserver correlation was good for radiographic evaluation of PTFJ (κ = 0.557). By intraobserver analysis with McNemar test, there was no statistically significant difference between the radiographic evaluations of PTFJ (p = 0.167). Arthritic grades of PTFJ and tibiofemoral joints were strongly correlated (Pearson coefficient r = 0.58, p < 0.001). No significant relation was found between type of PTFJ and grade of arthritis (χ² test, p = 0.42). In the light of these findings, the proximal tibiofibular joint should be evaluated for arthritic findings that may be responsible for lateral knee pain before a total knee arthroplasty operation is considered. The type of PTFJ is not related to the degree of this joint arthritis.