To investigate the correlation of joint line (JL) with different reference points after total knee arthroplasty (TKA) on clinical evaluation of knee joint function.

Cases of total knee arthroplasty treated with measurement osteotomy (MR) and PCL retained knee prosthesis in the orthopedic department of East Anhui people’s Hospital, Chuzhou, Anhui province, from May 2015 to May 2017 were retrospectively analyzed. JL changes were measured with fibular head, femoral adductor attachment and tibial tubercle as reference points, and the KSS score, ROM, and Feller patella score were evaluated before and 12 months after surgery. Correlation analysis between JL changes and KSS score changes, ROM changes and Feller patella score changes were conducted.

Compared with preoperative, KSS score, ROM and Feller patella scores were significantly increased after TKA (P<0.05). There was a positive correlation between the JL changes measured by the fibular head and the femoral adductor attachment (r=0.874, P<0.01). At 12 months after surgery, the JL changes measured with the tibial tubercle as the reference point has negative correlations with the changes of KSS scores (r=-0.521, P<0.01) and the Feller patella scores (r=-0.493, P<0.01).

JL changes measured with tibial tubercle as a reference point is negatively correlated with changes in knee KSS score and Feller patella scores after TKA, so measuring JL changes with tibial tubercle as a reference point may better evaluate the clinical function of knee joint after TKA than with fibular head or the femoral adductor attachment.