A 49-year-old woman presented with left knee pain of insidious onset for 11 months' duration and instability expressed as giving way. She had been diagnosed with autoimmune hepatitis at 33 years old and had been taking prednisolone from 10 to 30 mg per day for 16 years. At 11 months before her first visit, she started to feel knee instability. There was no traumatic event except that she tottered on a bus. Since then, she had repetitive episodes of giving way during activities of daily living (ADL). On physical examination, there was slight swelling of the knee. Lachman test and pivot-shift test were positive. Magnetic resonance imaging (MRI) showed an ACL rupture without other ligament injuries or meniscus tear. There was no evidence of knee OA in radiographs. Stress radiographs with an anterior drawer force of 15 kg revealed 11.9 mm anterior displacement of the tibia compared to that of the contralateral side. Diagnosis was spontaneous ACL rupture and anatomic double-bundle ACL reconstruction was done using autogenous semitendinosus graft. Arthroscopy revealed the ACL rupture but no meniscus tear or cartilage lesion. Two femoral tunnels were drilled within the native ACL femoral footprint through an anteromedial portal, and two tibial tunnels were drilled within the tibial footprint in an outside-in fashion. Two double-folded semitendinosus tendon grafts were prepared. After the femoral fixation with TightRope RT (Arthrex, Inc., Naples, FL), each graft was fixed at the tibial end with a Double-spike plate (DSP; MEIRA Corp., Nagoya, Aichi, Japan) under tension of 20 N at 20  of knee flexion. Range of motion exercise and partial weightbearing with a functional knee brace (Breg, Inc., Carlsbad, CA) was begun 6 days after surgery. Full weightbearing was allowed 22 days after the surgery.
Function and stability of the knee were assessed 1, 2, and 3 years after surgery. At the 1-year postoperative visit, she felt no instability of her knee. On physical examination, range of motion was 0  to 140 . Lachman test and pivot shift test were negative. Laxity measurement with anterior stress radiographs revealed 2.2 mm of side-to-side difference. At 2 years postoperatively, the values for the knee injury and osteoarthritis outcome score (KOOS) subgroups were 92 for pain, 86 for symptoms, 81 for ADL function, 65 for sport, and 56 for knee-related quality of life. On MRI examination 2 years after the operation, the reconstructed graft had a homogeneous low-intensity signal indistinguishable from that of the PCL or patellar tendon on sagittal T2 images, demonstrating matured ligamentization, and there was no evidence of bone tunnel enlargement. The Howell graft signal assessment, which would correlate with graft maturity, was grade II (Fig. 1). Three years later at the last follow-up the patient was free of complaints. Laxity measurement with Kneelax arthrometer of Biodex, using a 132 N load revealed 1.8 mm of side-to-side difference and 1.6 mm difference on anterior stress radiographs. There was no evidence of OA. KOOS subgroups were 92 for pain, 93 for symptoms, 96 for ADL function, 65 for sport, and 75 for knee-related quality of life, indicating improvement from the score at the 2-year visit. Lysholm score was 84, suggesting a good result. Tegner activity score was 3. Informed consent was obtained from the patient.