This term refers to knee hyperextension, also called back knee.

Knee hyperextension may be caused by injury to the cruciate ligaments; dashboard injury; joint disease; trauma; muscle weakness; hypermobility syndrome; or fracture.

Manifestations of the condition may include: pain; swelling; weakness; effusion; deformity; or instability.

Diagnostic measures involve a physical examination to include: stability testing; x-ray; magnetic resonance imaging (MRI); and range of motion testing, such as Lachman's test (normal range of motion for the knee is from 0 to 130° degrees for flexion, and from 120° to 0 degrees for extension). In addition, laboratory tests may be done to rule out non-mechanical disorders.

Conservative treatment involving initial immobilization with bracing, followed by mobilization, rehabilitation, and anti-inflammatory medications may be implemented. Surgery may also be indicated.

If the knee is stabilized, a return to pre-injury activity level may be possible. A long-term secondary or chronic instability of the knee may result if serious injury is untreated. Degenerative changes may occur.

• The rating schedule for musculoskeletal was updated on February 7, 2021. Protection still does apply and should be considered with existing evaluations (38 CFR 3.951(a)).

• When evaluating genu recurvatum, which involves hyperextension of the knee beyond 0 degrees of extension, under 38 CFR 4.71a, DC 5263

  • do not also evaluate separately under 38 CFR 4.71a, DC 5261, but

  • DO evaluate separately under other evaluations if manifestations that are not overlapping, such as limitation of flexion under 38 CFR 4.71a, DC 5260, are attributed to genu recurvatum, and

  • do not evaluate separately under 38 CFR 4.71a, DC 5257; however, if instability is manifested from genu recurvatum evaluate based on the criteria that will provide the highest evaluation.

• None.