The degree of severity of arthritis on an X-ray often does not correlate with symptoms. A person with a terrible looking X-ray of the knee may be completely symptom-free. Likewise, a person who shows minimal arthritis on an X-ray may be experiencing severe pain. This does not mean that one person is stoic and the other is a complainer. Different people have higher or lower thresholds for pain, depending on their body biochemistry and the synapses within their brain. Many factors influence the pain threshold in a given individual, including social support, depression, painful stimuli, and other potential biochemical and neuromodulating factors.
Someone who has severe cartilage degeneration may not have reached the point where the surrounding structures have become irritated and inflamed. If only cartilage is involved, there will be no pain because cartilage doesn't have any nerve endings. By contrast, the person with minimal X-ray findings of cartilage degeneration may just be unlucky enough to have the cartilage degrade in a pattern that allows pressure to be placed on the surrounding structures, leading to irritation and inflammation. Perhaps the synovium was already inflamed, or perhaps the bone was already compensating for increased pressure, and a tiny bone spur hooked a piece of the joint capsule or irritated a ligament.
