Cartilage survival of the knee strongly depends on malalignment: a survival analysis from the Osteoarthritis Initiative (OAI)

Abstract

Purpose Progression of osteoarthritis over time is poorly understood. The aim of the current study was to establish a timeline of “cartilage survival rate” per subregion of the knee in relation to mechanical alignment of the lower extremity. The study hypothesized that there are differences in progression of osteoarthritis between varus, valgus and physiologic lower extremity alignment. Methods Based on hip‐knee‐ankle standing radiographs at baseline, 234 knees had physiologic (180° ± 3°, mean 179.7°), 158 knees had varus (< 177°; mean 174.5°) and 66 knees valgus (> 183°; mean 185.2°) alignment (consecutive knees of the OAI “Index Knee” group, n = 458; mean age 61.7; 264 females). The Osteoarthritis Initiative (OAI; a multi‐center, longitudinal, prospective observational study of knee osteoarthritis [30] using MRIs) defines progressive OA as a mean decrease of cartilage thickness of 136 µm/year and a mean decrease of cartilage volume by 5% over 1 year (DESS sequences, MRI). A Kaplan–Meier curve was generated for osteoarthritis progression based on OAI criteria. Results Osteoarthritis progression based on volume decrease of 5% in varus knees occurred after 30.8 months (medial femoral condyle), after 37 months (medial tibia), after 42.9 months (lateral femoral condyle) and 43.4 months (lateral tibia), respectively. In a valgus alignment progression was detectable after 31.5 months (lateral tibia), after 36.2 months (lateral femoral condyle), after 40.4 months (medial femoral condyle) and 43.8 months (medial tibia), respectively. The physiological alignment shows a progression after 37.8 months (medial femoral condyle), after 41.6 months (lateral tibia), after 41.7 months (medial tibia) and after 43 months (lateral femoral condyle), respectively. Conclusion Based on data from the OAI, the rate and location (subregion) of osteoarthritis progression of the knee is strongly associated with lower extremity mechanical alignment. Level of evidence Level I (prognostic study).

Osteoarthritis year in review 2019: imaging

“…Studies have investigated potential risk factors for the progression of knee OA. Factors found to be associated with the progression of tibiofemoral OA include frontal plane malalignment on Xrays 29,30 , decreased bone mineral density on DXA 31 , effusion and synovitis 32e34 , mucinous changes in the anterior cruciate ligament (ACL) 35 , bone marrow edema lesions 34 , elevated cartilage T2 relaxation time 34 , trabecular microstructure deterioration 31 , and increased thigh muscle fat 36 on MRI, quadriceps muscle weakness 37 , hip abductor muscle weakness 38 , and knee pain39. Factors found to be associated with the progression of patellofemoral OA include frontal plane malalignment on X-rays 29 , patella alta 40 , tibia tuberosity to trochlear groove distance 41 , superolateral Hoffa's fat fad edema 42 , and meniscus tear and extrusion 43 on MRI, and quadriceps muscle weakness 44 .…”

Which Knee Phenotypes Exhibit the Strongest Correlation With Cartilage Degeneration?

“…Articular degeneration and the development of osteoarthritis are associated with a large social and economic burden, and they can cause physical and psychologic disability [31]. Although hip-knee-ankle angle measurements [1, 19] are commonly used to assess alignment abnormalities in the frontal plane [1, 5, 14, 19, 29, 37, 41], little is known regarding the specific effects of limb axis deformities and progression of osteoarthritis. Using Hirschmann et al’s [24, 25] classification system of different knee phenotypes to assess the FMA and TMA, rather than solely relying on hip-knee-ankle angle measurements, we aimed to find the exact association between the various phenotypes and articular degeneration.…”

“…Although current evidence relies solely on the hipknee-ankle angle to differentiate among neutral, valgus, and varus knees, recent studies have reported extreme variability in the native knee's alignment [2,8,10,22,24,25,34]. Although abnormal alignment of the limb segments in the frontal plane, among others [1,19], is commonly associated with the progression of knee osteoarthritis [5,14,29,37,41], the exact relationship between limb axis deformities and osteoarthritis remains poorly understood.…”

Lateral Knee Osteoarthritis

“…Stability maneuvers show laxity of the medial ligaments and shortening of the lateral ones, these are essential elements to be taken into account for treatment. [14,15] Radiography is of great help for the diagnosis, but it is important to remember that osteoarthritis is an entity in which the clinical and imaging features are not linear and symmetrical, hence there may be patients with marked degenerative changes on radiographs and have few symptoms or vice versa. On plain radiographs Fujisawa point should be calculated to determinate osteotomy and evaluate limb alignment after surgical procedures.…”