Knee Osteoarthritis (Gonarthrosis): Diagnostic Tests

Obligatory medical device diagnostics.

  • Radiographs of the affected joint [radiographic signs of arthritic joint remodeling: osteophytes (gonarthrosis: initially at the eminentia intercondylica), narrowed joint space, increased subchondral sclerosis and deformity; see below Kellgren and Lawrence score].

Optional medical device diagnostics – depending on the results of the history, physical examination, laboratory diagnostics and obligatory medical device diagnostics – for differential diagnostic clarification.

  • Magnetic resonance imaging (MRI; computer-assisted cross-sectional imaging method (using magnetic fields, i.e., without X-rays); particularly well suited for imaging soft tissue injuries) of the affected joint – allows visualization of cartilage and cartilage matrix changes as well as concomitant knee interior changes of the menisci, ligaments, and bone marrow; indications: especially in cases of cartilage and meniscus damageCaution (note): cartilage defects in the knee are usually more extensive intraoperatively
  • Computed tomography (CT; sectional imaging method (X-ray images from different directions with computer-based evaluation), particularly well suited to the representation of bony injuries) of the affected joint – findings correspond to the X-ray images, but earlier representation possible; better representation of complex structures.
  • Arthroscopy of the knee joint (arthroscopy) – If necessary, small tissue samples of the damaged cartilage or synovial fluid (synovial fluid) are taken and examined in the laboratory. If loose bone fragments or cartilage pieces are found during the examination, they can be removed by lavage (irrigation) during the same procedure.
  • Arthrosonography (ultrasound examination of joints) – this also reveals joint effusions, soft tissue processes and fluid accumulation in the joint. This examination is also performed before a puncture or injection. The joint effusions or fluid accumulations can then be treated with medication – if necessary also by puncture. Does not count among the methods of choice for osteoarthritis!

Kellgren and Lawrence score

Osteophytes Joint space Sclerosis Deformation Points
none or questionable none or questionable narrowed none none 0
unique unique light light 1
large advanced light with cysts distinctly 2
cancelled strong with cyst formation 3

Interpretation

According to the Kellgren-Lawrence score, the radiological expression of osteoarthritis is divided into five grades:

  • Grade 0 = 0 points
  • Grade 1 = 1 – 2 points
  • Grade 2 = 3 – 4 points
  • Grade 3 = 5 – 9 points
  • Grade 4 = 10 points

Grade 1: Minor subchondral sclerosis. No joint space narrowing or osteophytesGrade 2: Minor joint space narrowing and incipient osteophyte formation, indicated irregularities of the articular surfaceGrade 3: Marked osteophyte formation, marked irregularities of the articular surfaceGrade 4: Marked joint space narrowing to complete destruction, deformation/necrosis of the articular partners.

MRI-based definition of “osteoarthritis”

The definition of tibiofemoral osteoarthritis (gonarthrosis) was based on expert consensus:

A) The presence of both definite osteophyte formation (circumscribed new bone formation) and full-thickness (focal or diffuse) cartilage damage or
B) By the presence of any of the features in a) and any of the following structural changes:
  • Subchondral bone marrow lesion or cyst
  • Meniscal subluxation, maceration, or degenerative (horizontal) tear formation
  • Partial-layer focal or diffuse The definition of patellofemoral osteoarthritis requires the simultaneous presence of definite patellofemoral osteophyte and partial- or full-layer patellofemoral cartilage damage.

The definition of patellofemoral osteoarthritis requires the simultaneous presence of definite patellofemoral osteophyte and partial- or full-thickness patellofemoral cartilage damage.