The practice guideline 'Traumatic knee complaints' from the Dutch College of General Practitioners is aimed at differentiating between intra-articular and extra-articular lesions. The diagnosis is based mainly on a combination of patient history and a limited physical examination of the knee. Specific tests for hydrarthrosis, injuries to the collateral or cruciate ligaments, and meniscal pathology have only a low diagnostic accuracy. Few reliable studies have been conducted into the diagnostic value of specific tests; most studies employed poor methodology, had considerable inter-observer variation and produced widely heterogenous results. Inspection of the knee can provide information regarding the presence of fluids in the knee (hydrarthrosis or haemarthrosis). A restricted active range of movement in flexion and extension may indicate osteoarthritis or arthritis.