Knee injuries are one of the most common musculoskeletal complaints among veterans. Running, rucking, jumping, kneeling on hard surfaces, and the physical demands of military training and operations place extraordinary stress on the knee joint. Many veterans leave service with knee problems that worsen over the years, but establishing the nexus to service requires more than pointing to the pain.
Common Knee Conditions in Veterans
The knee conditions most frequently seen in VA disability claims include:
- Patellofemoral syndrome. Anterior knee pain caused by irritation of the cartilage under the kneecap. Extremely common in service members who run and ruck frequently.
- Meniscal tears. Tears of the cartilage cushions inside the knee joint, often from twisting injuries during training or operations.
- Ligament injuries. ACL, MCL, and other ligament tears or sprains from acute trauma.
- Degenerative joint disease (osteoarthritis). Progressive cartilage loss and joint deterioration, often the long-term consequence of earlier injuries and cumulative mechanical stress.
- Knee instability. Chronic laxity from ligament damage, separately ratable from the underlying condition.
The Service Connection Challenge
Like spine claims, knee claims face the "normal aging" defense. C&P examiners frequently attribute degenerative changes in a veteran's knees to age-related wear rather than military service. The nexus opinion must establish why the veteran's knee condition is service-connected by connecting specific in-service activities and documented injuries to the current pathology.
The strongest knee claims have documented in-service injuries or complaints in the service treatment records. But even without a specific documented injury, the cumulative physical demands of military service — particularly for combat arms, airborne, and physically demanding MOSs — provide a legitimate basis for a nexus opinion when supported by medical literature on occupational joint disease.
What the Nexus Letter Should Include
- The specific military duties, events, or injuries that placed abnormal stress on the veteran's knees.
- Any documented knee complaints, treatment, or profile limitations during service.
- The current diagnosis confirmed by physical examination and imaging.
- The medical mechanism connecting military service to the current condition.
- An explanation of why the condition exceeds normal age-related wear.
- Supporting medical literature on military-related knee injuries.
The Key Point
Knee conditions are common in veterans and common in the general population. The nexus opinion must differentiate between the two — explaining why this veteran's knee condition is the result of military service rather than ordinary aging. The more specific the clinical reasoning, the stronger the opinion.
Continue Reading: Knee Claims in Detail
Mechanism of Injury: Impact vs. Cumulative Stress
Military knee injuries generally fall into two categories, and the nexus argument differs for each:
Acute Traumatic Injuries
These include ligament tears, meniscal tears, fractures, and dislocations from specific events — a fall during an obstacle course, a vehicle accident, a parachute landing fall, or a sports injury during organized PT. If the injury is documented in service treatment records, the nexus is relatively straightforward: the in-service event caused the injury, and the current condition is the natural progression or residual of that injury.
Even when the acute injury appears to have resolved during service, a nexus opinion can explain how the initial trauma set the stage for accelerated degeneration. A meniscal tear that was treated conservatively during service, for example, alters the biomechanics of the joint and accelerates cartilage wear over subsequent years. The current osteoarthritis is a delayed but direct consequence of the in-service injury.
Cumulative Microtrauma
Many veterans never had a single acute knee injury during service. Instead, their knee condition results from years of repetitive impact — running on hard surfaces, rucking with heavy loads, kneeling on hard ground, climbing in and out of vehicles, and the general physical intensity of military training and operations. This cumulative microtrauma causes progressive cartilage damage, subchondral bone changes, and eventual osteoarthritis.
The medical literature supports this mechanism. Studies of military populations demonstrate higher rates of knee osteoarthritis compared to age-matched civilians, particularly in infantry, airborne, and other physically demanding MOSs. The nexus letter should cite this research and connect it to the veteran's specific service history.
Bilateral Knee Claims
Many veterans have bilateral (both knees) conditions. If the mechanism is cumulative stress from military duties, both knees were subject to the same demands, and both can be service-connected on the same basis. The nexus letter should address both knees individually, noting any asymmetry in findings and explaining it (e.g., the dominant leg bearing more weight during load carriage, or a prior injury to one knee altering gait and increasing stress on the contralateral knee).
Secondary Conditions from Knee Injuries
A service-connected knee condition frequently leads to secondary conditions that can be separately rated:
- Altered gait and contralateral knee or hip pain. Limping or favoring one leg shifts mechanical stress to the opposite knee, hip, and lumbar spine. These secondary conditions can be service-connected under 38 C.F.R. § 3.310.
- Lumbar spine conditions. Altered gait mechanics from knee pain change the biomechanics of the entire kinetic chain, including the lumbar spine. Many veterans with service-connected knee conditions develop secondary back problems.
- Weight gain and associated conditions. Veterans who can no longer exercise at the level they maintained during service due to knee pain often experience significant weight gain. This weight gain can contribute to sleep apnea, hypertension, and diabetes — all potentially claimable as secondary conditions.
- Mental health impacts. Chronic pain from knee conditions can contribute to depression and anxiety, particularly when the pain limits the veteran's ability to work, exercise, or participate in activities they previously enjoyed.
Surgical History and Its Implications
Veterans who underwent knee surgery during service — arthroscopic meniscectomy, ACL reconstruction, or other procedures — have strong documentation of the in-service condition. The nexus opinion should explain how the surgical intervention, while addressing the acute problem, did not restore the joint to its pre-injury state. Post-surgical knees develop osteoarthritis at significantly higher rates than uninjured knees, and this progression is a well-documented consequence of the original service-connected injury.
For veterans who had surgery after separation, the nexus letter should establish that the condition requiring surgery was present during service (or resulted from in-service events) even though the surgical treatment occurred later. Delayed surgical intervention does not negate the service connection — it reflects the natural history of progressive joint disease.
Rating Considerations for Knee Conditions
The VA rates knee conditions under several diagnostic codes, and understanding the rating structure helps ensure the claim captures the full extent of disability:
- Limitation of flexion (Diagnostic Code 5260) — rated based on how far the knee can bend.
- Limitation of extension (DC 5261) — rated based on how far the knee can straighten. Importantly, limitation of flexion and limitation of extension can be rated separately for the same knee.
- Instability (DC 5257) — rated separately from limitation of motion. A veteran with both arthritis limiting motion and ligament instability can receive separate ratings for each.
- Meniscal conditions (DC 5258, 5259) — dislocated or removed cartilage, rated based on symptoms.
The nexus letter should document all manifestations of the knee condition — range of motion limitation, instability, locking, giving way, effusion — to ensure the claim captures every ratable component.