A decrease or relaxation in tension of the knee ligaments.

Common causes may include the following:

• injuries,

• trauma,

• disease,

• genetic conditions,

• autoimmune disorders,

• repetitive overuse,

• excess weight-bearing stress, and

• normal aging. 

The following symptoms may occur:

• instability,

• subluxation,

• dislocation,

• weakness,

• decreased range of motion (ROM), and

• joint aching.

With injury there may be bleeding into the joint, swelling, bruising, or fracture.

Physical examination may be performed to include: inspection; palpation; stability testing; and range-of-motion (ROM) testing. X-ray, magnetic resonance imaging (MRI), and arthroscopy to confirm a diagnosis may be performed. Laboratory tests may be needed to evaluate non-mechanical disorders such as arthritis.

In the event of injury, initial treatment may include application of ice, elevation of the limb, and pain medication. Following initial treatment after injury heat may be applied, nonsteroidal anti-inflammatory drugs (NSAIDs) may be given, and mobility may be initiated with supportive devices such as a brace or splint to maintain stability. Physical therapy for strengthening exercises may be needed, or surgery may be indicated.

The potential for ligament tearing and repeated injury to other knee structures exists. The development of arthritis is possible. There may be a need to modify activities of daily living (ADL).

• Congenital or developmental defects refer to normally static, structural or inherent body abnormalities which are typically present at birth and are generally incapable of improvement or deterioration.  These include but are not limited to vertebral anomalies. Congenital or developmental defects are not diseases or injuries within the meaning of applicable legislation as outlined in 38 CFR 3.303(c) and 38 CFR 4.9. The M21-1 includes a section devoted entirely to this subject (Service Connection (SC) for Congenital, Developmental, or Hereditary Disorders). Diseases of congenital, developmental, or familial, hereditary origin may be subject to SC if they first manifest in service, pre-exist service but progress at a high rate during service, are presumptively related to service, or for disabilities resulting from an overlying injury or disease of a congenital defect.

• 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)).

• A meniscal disability may be rated separately under 38 CFR 4.71a, DC 5258/5259 apart from 38 CFR 4.71a, DC 5257 for manifestations of the knee disability other than recurrent subluxation and instability.

• See VAOPGCPREC 9-2004, VAOGCPREC 09-98, and VAOPGCPREC 23-97

• Instability, as referred to in 38 CFR 4.71a, DC 5257, includes patellar instability due to recurrent patellar subluxation or patellar dislocation, and/or any other instability or laxity of the knee that involves other stabilizing structure of the knee such as the collateral or cruciate ligaments. Subluxation refers to partial or incomplete dislocation of the knee joint (tibiofemoral dislocation/subluxation) or tendency for the patella to dislocate from its track (patellar dislocation/subluxation).

• For patellar instability, the patellofemoral complex consists of the quadriceps tendon, the patella, and the patellar tendon.

• A surgical procedure that does not involve repair of one or more patellofemoral components that contribute to the underlying instability shall not qualify as surgical repair for patellar instability (including, but not limited to, arthroscopy to remove loose bodies and joint aspiration).