Development of a hyaline cartilage thickness map of a normal knee joint and in knee varus and valgus deformity

Aim. Estimation of the average thickness of hyaline cartilage on the basis of magnetic resonance imaging for its further evaluation in standard radiography of the normal knee joint.

Methods. The study included 66 magnetic resonance imaging scans of healthy knee joints (30 right and 36 left joints) from 32 females and 34 males aged 35 to 59 years (mean age 47±8.1 years) with different limb axis deviation. All scans were processed manually using Syngo fastView programs to create a 3D model of the distal femoral epiphysis and the proximal tibial epiphysis, and also to differentiate between cartilage tissue and bone. The next step was measurement of hyaline cartilage thickness on the created models made at intervals of 2 mm to create a «thickness map» which later would make it possible to estimate the cartilage thickness on the basis of standard knee radiograph.

Results. The hyaline cartilage thickness varies depending on the sex and limb axis deformation. Thus, the largest thickness of cartilaginous tissue was observed on the articular surface of the femur in males 1.5-2 cm above the attachment site of the anterior cruciate ligament, and the average thickness on the femur was 1.90±0.425 mm. The largest thickness of the cartilage on the articular surface of the tibia in males was observed in the lateral side, and the average thickness was 1.64±0.434 mm. The cartilage thickness in the medial joint was significantly less in varus deformity than in valgus deformity.

Conclusion. The hyaline cartilage «thickness map» of the knee joint allows assessing its state by standard radiographs without performing magnetic resonance imaging; modification of hyaline cartilage «thickness map» in pathology will improve the treatment results for local defects and more reliably perform preoperative planning for needed knee replacement.