Knee problems in rheumatoid arthritis do not always receive the attention they deserve. The disease is commonly associated with swollen fingers, painful wrists and deformities of the small joints of the hands. The knee is sometimes treated as a secondary concern, although its involvement can have a much greater effect on mobility. Walking, standing, climbing stairs and getting out of a chair all depend on a joint that must tolerate repeated loading throughout the day. When chronic inflammation affects its internal structures, even ordinary movements can become difficult.
Rheumatoid arthritis develops through an abnormal immune response directed against the body’s own tissues. The synovial membrane becomes the main site of inflammation. Its cells proliferate, inflammatory cells accumulate and the production of cytokines increases. TNF, interleukin-1 and interleukin-6 participate in the processes responsible for cartilage degradation and bone resorption. In established disease, the inflamed synovium may form pannus, a layer of proliferating tissue that extends over the articular surfaces and contributes to progressive destruction.
The knee can remain swollen for a long time before major radiographic changes become visible. This is one reason why early assessment is sometimes difficult. The patient complains of stiffness, discomfort and reduced movement, but conventional imaging may show little more than periarticular osteopenia or a small reduction in joint space. The synovial membrane, meanwhile, may already be considerably thickened. Ultrasound can demonstrate this process more clearly, particularly when there is uncertainty about the relative contribution of synovial hypertrophy and joint effusion.
The clinical presentation varies. Some patients have bilateral knee involvement together with active inflammation in the hands and wrists. Others experience recurrent swelling predominantly in one knee. Morning stiffness is common, but its duration and severity are not reliable measures of structural damage. A patient may report less pain than previously while examination reveals persistent synovial thickening and restricted movement. Medication can suppress symptoms without reversing erosions that have already developed.
The orthopedic examination needs to establish what is happening inside the joint and how much its function has changed. Particular attention is paid to effusion, warmth, tenderness, range of motion and ligament stability. Quadriceps strength is equally important. Inflammation and pain can inhibit normal muscle activation, sometimes producing marked weakness even when the patient has not been inactive for very long.
A swollen knee also requires a proper differential diagnosis. Rheumatoid arthritis does not protect against infection, meniscal injury or calcium pyrophosphate crystal deposition. In patients receiving immunosuppressive treatment, septic arthritis may present with relatively modest systemic symptoms. An unexplained acute effusion, particularly when accompanied by increased warmth and pain, may require aspiration for synovial fluid analysis, including microbiological examination and crystal identification. Starting treatment for an assumed rheumatoid flare without considering infection can have serious consequences.
Radiographic assessment becomes particularly important when the disease has been present for several years. Marginal erosions, uniform narrowing of the joint space and loss of periarticular bone density are characteristic findings. Advanced destruction may involve both femoral condyles and the tibial plateau. Osteophytes are generally less prominent than in primary osteoarthritis, although degenerative changes can develop alongside rheumatoid damage. In older patients, separating the two processes is not always straightforward.
One of the changes that deserves more attention is the gradual loss of full knee extension. It may begin with discomfort during the final degrees of straightening. The patient rests with the knee slightly bent, avoids prolonged standing and changes the way weight is transferred through the leg. With persistent inflammation, the posterior capsule and surrounding soft tissues may become contracted. A fixed flexion deformity then develops, sometimes accompanied by shortening of the hamstrings.
The consequences extend beyond the knee. During walking, the joint normally approaches full extension during the stance phase, allowing the limb to support body weight efficiently. When this position is lost, the quadriceps must work harder and the patient may compensate through altered hip and ankle movement. Walking speed decreases. Fatigue appears sooner, particularly when the opposite leg is also affected. In advanced cases, the patient may struggle to stand upright without support.
Ligament damage creates a separate set of difficulties. Chronic synovitis and erosion around ligament attachments can compromise joint stability. The medial collateral ligament may become stretched, while progressive cartilage loss changes the distribution of forces across the knee. Valgus deformity is frequently encountered in advanced rheumatoid disease. Instability can become particularly troublesome when the patient turns, walks on uneven surfaces or descends stairs. A knee that is painful but stable requires a different approach from one with substantial ligament insufficiency.
Treatment begins with control of the autoimmune disease. Methotrexate is commonly used as a conventional disease-modifying antirheumatic drug. Biological agents and targeted synthetic drugs are available when disease activity remains insufficiently controlled. The choice depends on disease severity, previous treatment response and other medical factors. Orthopedic treatment cannot replace this part of management. A corticosteroid injection may reduce persistent inflammation in the knee, but it does not prevent systemic progression. Repeated injections also require consideration of their potential effects on cartilage and infection risk.
Physical rehabilitation has to account for the changing condition of the joint. Quadriceps weakness, reduced extension and loss of general endurance are common problems. Exercises should preserve movement and maintain muscle activity without repeatedly aggravating active synovitis. During an inflammatory flare, the patient may tolerate only gentle mobility work and limited weight-bearing activity. Later, when swelling decreases, strengthening and gait training can be increased. The difficulty lies in maintaining progress when the disease does not follow a predictable course.
Surgical intervention becomes an option when the knee has sustained extensive structural damage and pain or instability continues to restrict daily activity. Total knee arthroplasty is frequently performed in advanced rheumatoid arthritis. The procedure may be complicated by osteopenia, bone defects and damaged collateral ligaments. These findings influence the preparation of the femur and tibia, fixation strategy and choice of prosthesis. Cemented fixation is commonly used when bone quality is poor. Greater implant constraint may be required when the remaining ligaments cannot provide sufficient stability.
The correction of a longstanding deformity also requires attention to surrounding nerves and soft tissues. In a severe valgus knee, correction of alignment can increase tension on the common peroneal nerve near the fibular head. Postoperative assessment of ankle dorsiflexion and sensation over the foot is therefore important. Chronic corticosteroid exposure and systemic inflammation may also affect skin quality and wound healing. These factors need to be considered before surgery, not only after a complication appears.
Medication management around arthroplasty is another area requiring cooperation between specialists. Current ACR/AAHKS recommendations generally support continuing methotrexate during elective hip and knee replacement. Biological agents are usually withheld for one dosing interval before surgery and restarted when wound healing is satisfactory and there is no evidence of infection. The timing must be individualized. An inflammatory flare during the postoperative period can affect joints that are not involved in the operation, particularly the shoulders and wrists. This may interfere with the patient’s ability to use walking aids and participate in rehabilitation.
The first weeks after knee replacement can therefore be physically demanding even when the operation itself has gone well. The patient needs to regain knee movement, restore quadriceps control and learn to walk with the new joint. At the same time, other affected joints may limit the use of a walker or crutches. Reduced muscle mass and prolonged inactivity before surgery can further delay recovery. Rehabilitation cannot be planned around the operated knee alone.
Infection is another concern that remains relevant throughout postoperative follow-up. Patients with rheumatoid arthritis may have an increased risk of periprosthetic joint infection because of the disease itself, immunosuppressive treatment and associated comorbidities. Persistent wound drainage, increasing pain, warmth or unexplained swelling require investigation. A new episode of inflammation around a prosthetic knee should never be assumed to represent an ordinary rheumatoid flare without appropriate assessment.
Modern total knee prostheses have improved the possibilities of surgical treatment, and long-term implant survival in rheumatoid arthritis has become increasingly comparable with that in osteoarthritis. Still, a technically successful replacement does not necessarily restore the patient’s previous level of physical activity. Damage to other joints, longstanding muscle weakness and restricted movement may remain. The knee can be stable and relatively pain-free while walking continues to require considerable effort.
There is a particular difficulty in evaluating these patients over time. Inflammatory activity, structural damage and physical capacity do not necessarily improve together. Laboratory results may become normal while an established contracture remains. Synovitis may settle, but the ligaments may already have lost their supporting function. Even after replacement, the patient may continue to experience limitations caused by other affected joints. These are different aspects of the same disease, although they do not always respond to the same treatment.