Medial compartment arthrosis of the knee.

When the resultant forces on the tibial plateau are displaced medially, compressive stresses cause apposition of bony tissue, thus thickening the dense subchondral bone underlying the medial plateau. Loss of the articular cartilage and an increase in subchondral bone density facilitate the progression of osteoarthrosis. Surgical management is dependent on the presence of a varus deformity; patients with medial compartment disease and varus alignment should be considered for high tibial osteotomy (HTO) or unicondylar or total knee arthroplasty (TKA), depending on their age and activity level. Patients without varus deformity and with mechanical symptoms, only mild joint-space narrowing, and pain less than 1 year are likely to benefit from arthroscopic débridement. Patients without varus alignment but with chronic pain associated with loading and more pronounced joint-space loss should be considered for HTO, or unicondylar or TKA.