A 60-year-old woman (body weight: 45 kg, body mass index: 20.4 kg/m2) with severe PD presented with left knee pain. She was diagnosed with PD 12 years prior, and she had been medicated with several anti-PD medications. The symptoms of PD waxed and waned frequently. She often experienced the wearing-off phenomenon. Using a cane, she managed to remain standing and walk leaning the body to her left side. She had Pisa syndrome and scoliosis that were postural deformities of the trunk as symptoms of her PD (Figure 1). She required partial assistance throughout her daily life. Her Hoehn-Yahr scale was grade IV.
Her medical history included L1-L4 PLIF for lumbar degenerative spondylolisthesis and scoliosis to get rid of her leg pain, which was performed in another hospital one month prior to the gradual onset of her left knee pain (Figures 2(a) and 2(b)). Her hip joints showed bilateral acetabular dysplasia without pain. Two months after the gradual onset of left knee pain, she visited an orthopedic clinic. Knee joint punctures and intra-articular hydrocortisone injections were performed several times. Betamethasone sodium phosphate was injected at the first visit, and triamcinolone acetonide was injected at the second one. Despite conservative therapies, her knee pain worsened. She was barely able to crawl to the bathroom. Two weeks after the final injection, she presented to our hospital in a wheelchair.
The painful knee felt warm without swelling. A radiograph revealed moderate lateral osteoarthritis of the knee (Kellgren-Lawrence classification grade II) (Figure 3(a)). The range of motion preoperatively was 20 to 110 degrees. After repeated swelling and subsidence of the knee, the radiograph revealed progression to Kellgren-Lawrence grade IV in only 1 month (Figure 3(b)). Her white blood cell count and levels of C-reactive protein and procalcitonin were within normal limits. The erythrocyte sedimentation rate at the time of 60 minutes was 17 mm. Bacterial culture of the synovial fluid was negative. Candida and tuberculosis tests were also negative.
Magnetic resonance imaging (MRI) revealed partial depression of the joint surface including shredded ossicles and substantial amounts of synovial fluid. The T2-weighted coronal image revealed diffuse high-signal intensity, which suggested extensive spreading edema of the bone marrow and soft tissue (Figure 4). The change was considered to be caused by a SIF.
Bone mineral density measured at the femoral neck was 0.41 g/cm2. The T-score was very low (-3.5), suggesting severe osteoporosis.
Based on the physical findings, laboratory data, and imaging findings on admission, rheumatoid arthritis and pyogenic arthritis were ruled out. Although there are few reports about Charcot spine and Charcot foot associated with PD, to the best of our knowledge, no publications have reported Charcot joint of the knee related to PD. It was therefore very difficult to arrive at the hypothesis that PD was the basal disease causing Charcot's joints. Yamamoto and Bullough concluded that SIF is the primary event leading to spontaneous osteonecrosis with histopathological study. Moreover, the histopathological findings of SIF are similar to those of spontaneous osteonecrosis. However, the destruction of the joint surface was too rapid to enable the diagnosis of spontaneous osteonecrosis of the knee.
Finally, we diagnosed her with SIF of the knee on the basis of rapidly progressing destructive osteoarthritis within only a month. The MRI findings also supported the diagnosis of SIF. The SIF was also considered to be an initial symptom of steroid arthropathy because it occurred after intra-articular hydrocortisone injection. Steroid arthropathy was first described by Chandler et al. and is characterized by rapidly destructive osteoarthritis. Hydrocortisone induces cartilage degeneration and bone atrophy. Pain relievers cause lack of perception feedback, due to which excess loads are often applied to knee joints. Steroid arthropathy of the knee is understood to occur as a result of pathological osteochondral fractures caused by increased mechanical stress. Steroid arthropathy needs to be identified with idiopathic osteonecrosis clinically and histopathologically. In this case, we did not perform the histopathological examination and could not certify the mechanism of SIF. However, rapid destructive steroid arthropathy might be conceivable to make the SIF.
Osteotomy or bone grafting would not have sufficiently reduced the pain and osteochondral remodeling because the joint surface was extensively destroyed and there was severe valgus alignment. Considering the patient's age, the level of activity, and the advanced stage of PD, total knee arthroplasty (TKA) was performed under general anesthesia.
TKA was performed using the medial parapatellar approach under general anesthesia. More bone than usual was resected because there was a severe extension contracture. Because the extension gap was tight on the lateral side, iliotibial band resection was added. There were severe bone atrophy and fragility in the medial epicondyle of the femur. The surface of the cartilage easily depressed under finger pressure. The cartilage of the lateral joint surface was scooped out and partially eburnated (Figure 5(a)). TKA was performed using a stemmed semiconstrained prosthesis (Attune Revision, DePuy Synthes, Warsaw, IN) because of concern for the failure of the medial collateral ligament caused by severe bone fragility in the medial epicondyle of the femur (Figures 5(b) and 5(c)). There were a satisfactory intraoperative implant gap, joint balance, and patella tracking. Prior to surgery, the poor mobility in her hip joint was thought to be affected by rigidity related to her PD. However, the poor mobility did not improve under general anesthesia. Her adductor longus tendon was resected because there was a hip adduction contracture. There was no particular restriction after treatment.
Her gait posture improved; however, postural deformities remained. There were no complications during hospitalization. There has been no early loosening of the prosthesis at the final follow-up: fifteen months after TKA.
She was able to walk with a cane and without knee pain. Her preoperative visual analogue score of 100 mm changed to 0 mm postoperatively. The preoperative range of motion was 25 to 110 degrees. This improved to 5 to 130 degrees postoperatively. A mild flexion contracture remained. The total alignment of the lower extremity improved dramatically after TKA and resection of the adductor longus tendon of the hip. The preoperative hip-knee-ankle angle (HKA angle) (-16 degrees while standing) was corrected to postoperative HKA angle (-2 degrees; positive values indicate the varus direction) (Figure 6).