Same parameters of bone and inflammatory disorders. They are; Rheumatoid factor, CRP, ESR, Alkaline phosphatase, ACPA, ANA. These are normally requested by the doctors. If you want to do a research project, I prefere cytokines and soluble receptors. GOOD LUCK.
To answer the question fully you need to look at what the healthy joint does/ can do, and what alterations are effects of OA arise. For example, OA is a capsular condition (see work by Dr James Cyriax) i.e. it affects the kinematics of the joint capsule and evidence suggests that the knee loses more flexion than extension. The nature of the condition will also suggest less VGRF bearable by the joint, meaning it may create an antalgic gait. These two factors mean that other joints may be affected, if this is a factor you are looking to investigate.