Objectives Objective: 1. To assess the patterns of US evaluation of Knee joint osteoarthritis. 2. To evaluate the use of US as a tool for quantitative assessment of knee trochlear cartilage thickness 3. To assess whether US changes vary and can be used to stratify early versus advanced osteoarthritis of the knee joint.
Methods 82 patients with OA of the knee (69% female; mean age 66.4 years) and 44 healthy (70% female; mean age 64.5 years) were recruited. The OA stage was determined according to the Kellgren/Lawrence (K/L) radiographic grading system. Knee joint US was carried out to assess for: 1. the cartilage clarity as well as the sharpness of the cartilage-synovial interface. 2. Cartilage thickness measures: the distance between the trochlear notch and the convexity of the medial trochlea was divided into 3 equal divisions and articular cartilage thickness was measured. 3. The presence of osteophytes. 4. synovitis and effusion. 5. medial and lateral meniscus displacement performed with subjects in the supine and standing positions.
To assess for the reliability of US measures, the thickness at the medial and lateral condyles was measured and ICCs were calculated. To assess for the validity: κ was calculated for the agreement between US and radiographs on osteophytes.
Results Five main changes in knee joint OA were identified: reduced sharpness of the anterior cartilage margins, loss of cartilage transparency, medial compartment cartilage thinning, displacement of the medical meniscus and abnormalities of the subchondral bone.
Radiographic abnormalities defined by K-L criteria were: K-L1 =15%, K-L2 =27%, K-L3 =41%, K-L4 =17%. Radiographic osteophytes were present in 44% of subjects. US showed osteophytes that were not seen in X-rays of 29%. whereas joint space narrowing was seen in 27% of the patients (p<0.02). Meniscal displacement and synovitis were significantly associated with higher pain scores (p<0.01).
There was a significant difference (p<0.01) between cartilage thickness at the last third of the medial mensicus in the patients versus controls (p<0.01). There was also significant difference (p<0.01) for both decreased cartilage clarity and sharpness of the cartilage-synovial interface in the patients versus control groups.
Reliability: high kappa values for osteophytes (0.96), cartilage thickness (0.88) and Medial Meniscus Displacement measures (0.83). Validity: when comparing radiograph results with those of the US, the corresponding kappa values were 0.45 on the right and 0.57 on the left; demonstrating moderate agreement.
Patients with early OA had: Indistinctness of the cartilage – synovial interface and loss of the clarity of the cartilage. Moderate OA patients had: moderate cartilage thinning, moderate Medial Meniscus displacement with/without osteophytes up to 2mm in length Advanced OA patients had: 1 and 2 plus severe Cartilage thinning or Medial Meniscus Displacement, osteophyte formation (>2mm in length) and irregularity of the subchondral bone.
Conclusions US scanning can replace plain radiographs in the evaluation of OA of the knee joint in the clinical practice of rheumatology. US not only shows the cartilage changes reliably enough, but also the existence of osteophytes and signs of inflammation e.g. effusion and synovial hyperplasia.
Disclosure of Interest None Declared