Realignment osteotomy, microfracture and chondroplasty
Knee alignment has a profound effect on the forces going through each compartment of the knee. Varus alignment (bow legs) increases the forces on the medial (inside) half of the knee and valgus alignment (knock knees) increases the forces of the lateral (outside) half of the knee. With progressive arthritis is an isolated compartment, the malalignment worsens, which further exacerbates the arthritic symptoms.
In younger (<60yo), active individuals with isolated arthritis and associated malalignment (usually medial arthritis and bow leg), correction (or slight overcorrection) of the alignment can unload the arthritic compartment and take the weight through the non-arthritic part of the knee. This aims to provide symptomatic relief whilst preserving the native knee and delaying the need for knee replacement in the medium future.
The osteotomy (cut bone) is usually done in the proximal tibia (shin bone), so is known as a high tibial osteotomy (HTO). It involves partially cutting the bone under controlled conditions, correcting the alignment and then fixing the newly created “fracture” with a plate and screws until the osteotomy heals.
Osteotomy is usually combined with simultaneous arthroscopy to assess the wear and tear in the remainder of the knee and treat any associated mechanical symptoms that arise from meniscal tears or loose bodies. Localised cartilage damage can be managed with microfracture (drilling the base of the cartilage defect to stimulate the underlying bone marrow healing response) or chondroplasty (trimming and sealing the edges of localised cartilage damage to attempt to prevent propagation of loose cartilage flaps).