We encountered a case in which improving limited knee flexion was difficult after surgery for a femoral shaft fracture. A woman in her 20s sustained polytrauma including a femoral shaft fracture. Anterograde intramedullary nailing of the femur was performed at another hospital on the day after the injury, and 75 days later she was transferred to our hospital for rehabilitation. The referral document indicated the fracture was an AO type C2 fracture, and postoperative plain radiographs showed that one of the locking screws in the distal femur was inserted from the anterior to posterior side. She was discharged to home at 90 days post-injury, but knee joint flexion was still limited to 95°, and she complained of pain in the final flexion range where a side-stop screw was inserted at the front of the knee. Imaging and physical findings indicated that knee flexion was restricted by contracture of the suprapatellar supporting tissues, so an approach focusing on these tissues was added to her outpatient exercise regimen. As a result, knee flexion was improved to 150° at 140 days post-injury and she had no interference in activities of daily living.

The infrapatellar fat pad is functionally deformed with joint movement and is involved in adjusting the internal pressure of the knee joint. On the other hand, it can also become a source of anterior knee pain due to inflammation and degeneration. A young female handball player experienced anterior knee pain. No obvious abnormality was observed on basic X-ray and magnetic resonance images. Dynamic observation using ultrasonic diagnostic imaging showed poor kinetics with infiltration of the infrapatellar fat pad into the patellar ligament and the tibial condyle, with the knee joint in extension on the affected side compared with the normal side. Knee joint range of movement (affected side vs. normal side) was restricted to 140° p / 150° flexion and extension - 10° p / 5°, and there was infrapatellar tenderness in the affected region. Patella baja was confirmed compared with the normal side. In addition, the flexibility of the infrapatellar fat pad was reduced. From these findings, it was inferred that the cause of pain was restriction of knee joint extension due to reduced flexibility of the infrapatellar fat pad. Treatment of the infrapatellar fat pad, joint range training exercises, and muscle strengthening training exercises were carried out. Pain and restricted range of joint movements improved and the patient could returned to competitive sports.