Orthopaedic Deformities: Knee Focus

Study Notes

Genu Varum (Bow Legs):
- Occurs when the legs curve outward at the knees, and ankles touch.
- Common in infants and toddlers.
- In genu varum, the anatomic tibiofemoral angle (aTFA) is greater than 173–175°.
- The mechanical axis from the femoral head to the ankle is lateral to the center of the knee joint.
- In infants, genu varum may be developmental and often corrects itself within 4 years.
- In children aged 1.5-2 years, rickets (vitamin D deficiency) is the common cause.
- Treatment for rickets involves addressing vitamin D deficiency.
- In adults, genu varum can be caused by osteoarthritis, mal-united fracture, ligamentous injury, and Paget's disease.
Genu Valgum (Knock Knees):
- Occurs when the knees angle inward and touch.
- Occurs when the mechanical axis from the hip to the ankle passes to the outside of the knee.
- Valgus knee in children under 4 years is usually developmental and often corrects itself by 6-8 years.
- If genu valgum persists, a supracondylar osteotomy of the femur might be necessary.

The normal neck-shaft angle of the proximal femur is 160° at birth, decreasing to 125° in adulthood.
Coxa Vara:
- An angle less than 110° between the head and shaft of the femur.
- Results in leg shortening and a limp.
- Can be congenital or caused by injury.
Coxa Valga:
- An angle greater than 130° between the head and shaft of the femur.
- Both coxa vara and coxa valga can lead to gait disability, spinal pain, and deformity.
- Treatment involves corrective subtrochanteric osteotomy.

Carrying Angle:
- The angle between the long axis of the extended forearm and the long axis of the arm.
- Normal carrying angle is 10-15 degrees of valgus, which allows for carrying objects.
Cubitus Varus:
- Excessive inward angulation (medial angulation) of the distal segment of the elbow.
Cubitus Valgus:
- Excessive outward angulation (lateral angulation) of the distal segment of the elbow.
Deformities are corrected surgically through a wedge osteotomy at the lower humerus.

Bone is a type of connective tissue composed of cells and a matrix.
Bone cells include osteoblasts (bone-forming) and osteoclasts (bone-resorbing).
The bone matrix is called osteoid and contains collagen with deposited calcium salts.
Causes of Bone Softening Diseases:
- Defective osteoid formation (e.g., osteogenesis imperfecta).
- Defective osteoid mineralization (e.g., rickets).
- Increased bone resorption.