The knee is a condylar joint, meaning that it is not a pure hinge joint like the elbow, but can twist as well. There are lots of ligaments holding the knee together. It also has a cushion in between the joint called a meniscus. The other unique feature is the patella (knee cap), which acts as a mechanical lever for the quadriceps. Unfortunately, all these structures can potentially be damaged.
Unlike the back and neck, a more specific diagnosis is required with the knee, as treatment can greatly differ depending on which structures are damaged. Various clinical tests are usually performed by the physiotherapist in an attempt to obtain a diagnosis. Referral for scans such as MRI (magnetic resonance imaging) are sometimes required, which the physiotherapist can organise for you.
The nastier injuries which may require surgical intervention are some meniscal tears or cruciate ligament injuries. There is usually a definite twist and sudden onset of pain with these injuries.
Pain at the front of the knee may be coming from the patella. The cause is often a mal-tracking of the patella laterally (outwards). There is strong evidence to suggest physiotherapy modalities such as taping, joint manual mobilisation, and quadriceps strengthening is effective in treating this.
Osteoarthritis (joint wear and tear) can sometimes be treated with physiotherapy. This is particularly so if it primarily involves the patella. There is evidence to suggest strengthening the quadriceps is beneficial.