This study was to evaluate the radiological and clinical mid-term results and the presence of post-traumatic osteoarthritis after osteosynthesis in patients under the age of 50 years undergoing osteosynthesis for distal femur intra-articular fractures (AO/OTA 33-B & C) from high-energy trauma.

Between January 2008 and January 2013, a total of twenty-one patients with more than three years of follow-up were enrolled. Recovery of the alignment of the lower extremity, union period, and the presence of post-traumatic osteoarthritis were confirmed by follow-up radiographs. Clinically, the range of motion, pain on fracture lesion, and Knee Society score (KSS) were evaluated.

The average duration of union was 18.2 weeks (10-28 weeks), and the alignment of the lower extremity was within normal range in all patients. Seven patients showed post-traumatic osteoarthritis at the final follow-up after more than three years. The presence of post-traumatic osteoarthritis was associated with the classification of fractures, coronal plane fracture, and age. The average range of motion, knee score among KSS, and function score at the last follow-up were 128.7°, 86.1, and 85.1, all showing a greater improvement when compared with the one-year follow-up scores.

The mid-term result was radiologically and clinically satisfactory. Furthermore, only 33.3% of patients showed a slight progress of post-traumatic osteoarthritis, which critically effects the prognosis.