Rheumatoid arthritis of the knee

Knee anatomy – what is inflamed in RA

The knee joint consists of the femur, tibia, patella, stabilizing ligaments, menisci and the joint capsule. The inner layer of the capsule, the synovial membrane, produces synovial fluid. In rheumatoid arthritis, this synovial membrane in particular becomes inflamed.

• Synovium: forms synovial fluid, becomes inflamed and thickens (synovitis).
• Cartilage: can be damaged secondarily by inflammatory mediators.
• Bones: Risk of erosion at the edges of the joints.
• Soft tissues: Ligaments and capsule may become lax; Baker's cysts are possible.

What does rheumatoid arthritis of the knee mean?

RA is an autoimmune disease. The immune system attacks the body's own structures, especially the lining of the joints. In the knee this leads to swelling, warmth, effusion and pain. The disease is usually symmetrical and can affect multiple joints; However, in some patients, knee involvement initially appears unilateral.

• Autoimmune mediated: Cytokines such as TNF-α and IL-6 drive inflammation.
• Systemic: fatigue, slight fever, weight loss possible.
• Chronic course: phases with attacks and quieter intervals.

Typical symptoms and course

• Pain and tenderness in the knee, often independent of load.
• Morning stiffness > 30 minutes, improvement over the course of the day.
• Swelling/effusion with a feeling of tension behind the kneecap.
• Feeling of warmth, occasionally redness.
• Loss of function: limping, difficulty climbing stairs.
• Baker's cyst in the back of the knee with pulling in the calf.

If left untreated, cartilage damage, ligament laxity, misalignment and permanent movement restrictions can occur. Early diagnosis and treatment are crucial to prevent structural damage.

Warning signs: When to see a doctor immediately

• Suddenly very painful, hot knee with fever: suspected joint infection - emergency.
• Known RA, now highly acute effusion after minor injury: infection or hemarthrosis possible.
• Severe calf pain/swelling: rupture of a Baker's cyst or deep vein thrombosis - investigate.
• Rapid general deterioration, chills, new skin rashes: medical assessment.

Diagnostics in our practice in Hamburg

We combine clinical examination, imaging procedures and laboratory values. If RA is suspected, diagnostics are carried out in close collaboration with rheumatology. The aim is to document inflammatory activity, rule out other causes and initiate early therapy.

• History: Duration of morning stiffness, relapse pattern, involvement of other joints, previous illnesses, medications.
• Clinical: Swelling, tenderness, range of motion, instability, popliteal fossa (Baker's cyst).
• Laboratory: CRP/BSG, rheumatoid factor, anti-CCP antibodies; Blood count, liver/kidney values ​​as a basis.
• Joint ultrasound: detection of effusion, synovitis, hypervascularization (power Doppler).
• X-ray: exclusion of other causes, assessment of erosions and joint space.
• MRI (if necessary): soft tissue and bone marrow edema, early erosions.
• Joint puncture: Diagnostic and therapeutic; Analysis of cell count, crystals, culture if infection is suspected.

ACR/EULAR criteria, which take into account joint involvement, serology and inflammation values, are often used to classify RA. These serve as orientation and do not replace clinical assessment.

Conservative therapy: the basis of our treatment

Conservative measures are the focus. They aim to relieve pain, reduce inflammation, maintain mobility and ensure joint function in everyday life.

• Activity control: dose the load, plan breaks, avoid overload - complete rest rarely makes sense.
• Cold in the acute phase, warmth in subacute phases – test individually.
• Physiotherapy: Improve mobility, muscular stability (quadriceps, hips), gait.
• Bandage or soft orthosis to control irritation; Cane/sticks temporarily for relief.
• Insoles/shoe advice: Axle steering and damping depending on the findings.
• Weight management: Just a few kilograms less can significantly relieve the strain on the knee.
• Smoking cessation: Smoking increases RA activity and reduces treatment response.
• Pain management: NSAID/COX-2 inhibitors for a limited time and after risk-benefit assessment.

Drug treatment (in coordination with rheumatology)

Long-term control of RA is carried out in accordance with guidelines using disease-modifying anti-rheumatic drugs (DMARDs). This setting is usually carried out by rheumatology. We coordinate local knee treatment and work together as a team.

• Important safety aspects: Regular laboratory checks, note the risk of infection, individual risk assessment.
• Always discuss pregnancy planning with rheumatology in advance (a change of medication may be necessary).

Joint puncture and injections on the knee

A sterile puncture provides relief from effusion, enables diagnosis and can quickly relieve pain. In selected cases, an intra-articular glucocorticoid injection is added to locally calm an attack.

• Indications: pronounced effusion, strong local attack, unclear diagnosis (crystals, infection).
• Implementation: under sterile conditions, with ultrasound support if necessary, short follow-up observation.
• Benefits: rapid pain relief, better range of motion, less capsular tension.
• Risks: rarely infection, bleeding, temporary irritation - information must be provided in advance.

Hyaluronic acid is not recommended as standard in RA; the evidence is inconsistent. Regenerative procedures such as PRP/ACP are not sufficiently proven for RA and should - if at all - only be considered in individual exceptional cases and after detailed information.

Training and physiotherapy: stay mobile

Targeted training reduces pain, improves stability and supports DMARD therapy. What is important is low-stimulation, regular exercise with a gradual increase.

• Mobility: gentle mobilization, active stretching/flexion exercises.
• Strength: Quadriceps, hamstrings, hip abductors – 2-3×/week.
• Endurance: Light load cycling, swimming/aqua fitness.
• Coordination: balance training for gait stability.
• Pacing: reduce intensity on push days and increase intensity on quiet days.

Everyday life and self-management

Your everyday life is part of the therapy. Small adjustments help calm inflammation and protect the knees.

• Adjust the workplace ergonomically: seat height, breaks, alternation between sitting/standing.
• Approach weight loss gradually; Mediterranean-emphasized diet.
• Good shoes with cushioning; If necessary, heel lift/insoles.
• Use heat/cold according to personal preference.
• Plan travel/vaccinations in advance if you are on immunosuppressive therapy (inactivated vaccines preferred, consultation with rheumatology).

Surgical options – only if there is a clear indication

If consistent conservative therapy and adequate DMARD adjustment do not sufficiently control the knee inflammation or if structural damage already exists, operations can be discussed. The decision and timing are individual and interdisciplinary.

• Arthroscopic synovectomy: removal of inflamed synovium in persistent local synovitis; The aim is to reduce inflammation.
• Radiosynoviorthesis (RSO): Nuclear medicine procedure; in selected cases and specialized centers.
• Knee endoprosthesis (TEP): For advanced destruction and failure of non-surgical measures. Realistic goal setting and follow-up care are crucial.

Every operation carries risks (infection, thrombosis, stiffness). We discuss benefits and alternatives together and attach great importance to good follow-up treatment with physiotherapy.

Prognosis, follow-up and goals

Thanks to modern therapy concepts, disease activity can often be significantly reduced. A treat-to-target approach with clear goals (remission or low disease activity) improves long-term prognosis.

• Regular checks: clinic, ultrasound if necessary, functional scores.
• Early adjustment of therapy if control is inadequate.
• Everyday goals: pain-reduced mobility, safe ability to climb stairs and walk, participation in work and leisure time.
• Long-term: Avoidance of structural damage and misalignment.

Differential diagnoses of the knee

Not all knee inflammation is RA. A clear demarcation prevents incorrect treatment.

• Activated knee osteoarthritis (gonarthrosis).
• Crystal arthropathies: gout, pseudogout (CPPD).
• Psoriatic arthritis, reactive arthritis.
• Septic arthritis (joint infection) – emergency.
• Meniscus/ligament lesions with reactive synovitis.

This is how we support you in Hamburg

We offer structured, conservative knee care with clear information and close collaboration with rheumatology. Joint ultrasound, puncture/injection therapy and physiotherapy concepts are fixed components. You can easily get appointments online or by email.