1. Effusion in a joint will be defined as a hypoechoic area within the hyperechoic joint capsule. Such anechoic intra-articular fluid will be displaceable by pressure of the US probe. This helps distinguish joint fluid from intra-articular hyaline cartilage, which is also anechoic to hypoechoic in appearance but is not displaceable by pressure of the probe. The distension of the joint capsule will be measured using sonographic calipers. This distension will be compared with normal values to assess the degree of effusion.