Genu recurvatum

Updated on Oct 08, 2024

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ICD-10 M21.8, Q68.2		ICD-9-CM 736.5, 754.40

Specialty medical genetics, rheumatology

Genu recurvatum is a deformity in the knee joint, so that the knee bends backwards. In this deformity, excessive extension occurs in the tibiofemoral joint. Genu recurvatum is also called knee hyperextension and back knee. This deformity is more common in women and people with familial ligamentous laxity. Hyperextension of the knee may be mild, moderate or severe.

The normal range of motion (ROM) of the knee joint is from 0 to 135 degrees in an adult. Full knee extension should be no more than 10 degrees. In genu recurvatum (back knee), normal extension is increased. The development of genu recurvatum may lead to knee pain and knee osteoarthritis.

Causes

The following factors may be involved in causing this deformity:

Inherent laxity of the knee ligaments

Weakness of biceps femoris muscle

Instability of the knee joint due to ligaments and joint capsule injuries

Inappropriate alignment of the tibia and femur

Malunion of the bones around the knee

Weakness in the hip extensor muscles

Gastrocnemius muscle weakness (in standing position)

Upper motor neuron lesion (for example, hemiplegia as the result of a cerebrovascular accident)

Lower motor neuron lesion (for example, in post-polio syndrome)

Deficit in joint proprioception

Lower limb length discrepancy

Congenital genu recurvatum

Cerebral palsy

Multiple sclerosis

Muscular dystrophy

Limited dorsiflexion (plantar flexion contracture)

Popliteus muscle weakness

Connective tissue disorders. In these disorders, there are excessive joint mobility (joint hypermobility) problems. These disorders include:

Marfan syndrome

Ehlers-Danlos syndrome

Benign hypermobile joint syndrome

Osteogenesis imperfecta disease

Knee stabilization

The most important factors of knee stability include:

Ligaments of the knee: The knee joint is stabilized by four main ligaments:

Anterior cruciate ligament (ACL). The ACL has an important role in stabilization of knee extension movement by preventing the knee from hyperextending.

Posterior cruciate ligament (PCL)

Medial collateral ligament (MCL)

Lateral collateral ligament (LCL)

Joint capsule or articular capsule (especially posterior knee capsule)

Quadriceps femoris muscle

Appropriate alignment of the femur and tibia (especially in knee extension position )