Definition of Tricompartmental Arthrosis
Tricompartmental arthrosis (or tricompartmental osteoarthritis) is degenerative joint disease affecting all three compartments of the knee: the medial tibiofemoral, lateral tibiofemoral, and patellofemoral compartments, characterized radiographically by joint space narrowing, osteophyte formation, subchondral sclerosis, and cyst formation across the entire joint. 1
Anatomical Components
The knee joint consists of three distinct compartments that can be affected by osteoarthritis 2:
- Medial tibiofemoral compartment: The space between the medial femoral condyle and medial tibial plateau, which bears 70-80% of joint load during gait and is the most frequently affected compartment 1
- Lateral tibiofemoral compartment: The space between the lateral femoral condyle and lateral tibial plateau, which is relatively protected compared to the medial compartment and affected in only approximately 10% of isolated knee OA cases 3
- Patellofemoral compartment: The articulation between the patella and femoral trochlea, which is one of the most commonly affected compartments and frequently a source of symptoms 4
Radiographic Features
Tricompartmental disease demonstrates pathological changes across all three compartments simultaneously 1:
- Joint space narrowing: Loss of cartilage thickness visible as reduced distance between bone surfaces in all compartments 1, 2
- Osteophyte formation: Bony outgrowths at joint margins present across multiple compartments 1, 2
- Subchondral sclerosis: Increased bone density beneath the articular cartilage 2
- Cyst formation: Subchondral bone cysts visible on radiographic imaging 2
Disease Conceptualization
Research demonstrates that tricompartmental arthrosis represents both a multicompartmental disease process and compartmental disease processes occurring simultaneously 2:
- Multicompartmental factor: Radiographic features across the entire joint show associations, suggesting a generalized disease process affecting the whole knee 2
- Compartmental factors: Each compartment also demonstrates specific associations among features within that compartment, indicating localized disease processes 2
Clinical Significance
The presence of tricompartmental disease has important treatment implications 1:
- Surgical management: Total knee arthroplasty (TKA) is indicated for tricompartmental degenerative changes, as demonstrated in the AAOS clinical practice guideline case example of a 67-year-old woman with moderate to severe tricompartmental disease 1
- Distinction from unicompartmental disease: Unicompartmental knee replacement is appropriate only for isolated compartmental disease with intact anterior cruciate ligament, not for tricompartmental involvement 5
- Disease severity: At the time of surgery, 17% of patients have tricompartmental disease, and most patients with Kellgren-Lawrence grade >3 demonstrate involvement of multiple compartments 6
Common Risk Factors
Multiple factors increase the risk of developing tricompartmental arthrosis 1:
- Age: Nearly one in two people develop symptomatic knee OA by age 85 years 1
- Obesity: Elevated body mass index significantly increases risk 1
- Trauma: Previous knee injury contributes to development 1
- Genetic predisposition: Hereditary factors play a role 1
- Occupational factors: Certain occupations increase risk 1