Transosseous Endoscopy for Bone Grafting of Proximal Tibial Bone Cysts

Case: A 43-year-old man with a history of previously treated Lyme arthritis presented with persistent right knee pain for 2 years.Imaging demonstrated synovitis and large subchondral cystic lesions in the proximal tibia and distal femur, suggestive of postinfectious Lyme arthritis (PILA).He underwent right knee arthroscopic synovectomy and transosseous endoscopic bone grafting.Notable improvements in knee pain and range of motion were observed at 1 year postoperatively.Conclusion: Transosseous endoscopic bone grafting of subchondral bone cysts can improve symptoms and restore periarticular bone stock without compromising intact cartilage at the time of arthroscopic synovectomy for PILA.Level of Evidence: V Case Report. Postinfectious Lyme arthritis (PILA) is a late manifestation of Lyme disease, which results in joint pain, synovitis, and eventually chronic erosive disease of the large joints, including the knee. 1 For patients with PILA, arthroscopic synovectomy can be used to reduce knee inflammation and pain.However, patients with structural damage to the cartilage and subchondral bone in the distal femur and proximal tibia may have less improvement after arthroscopic synovectomy because these structural abnormalities can be a potential source of ongoing pain, abnormal subchondral loading, and knee dysfunction. 2urthermore, the underlying bone loss can subsequently lead to complications such as intraoperative fracture and aseptic loosening in the event of a total knee arthroplasty (TKA). [3][4]4][5] Therefore, reconstitution of large subchondral cysts of the distal femur and proximal tibia with bone grafting may be used to improve pain and potentially reduce the risk of future complications of TKA.This report presents the case of a patient with persistent subchondral cyst formation of the proximal tibia and distal femur in the setting of PILA, who was treated with arthroscopic synovectomy and transosseous endoscopic bone grafting.