Knee pain is a common problem, accounting for 1.9 million visits to primary care practitioners and 1 million visits to emergency departments annually. By following a systematic approach in evaluating knee pain (which includes obtaining a thorough and directed history), focusing on specific questions, using the physical examination (sometimes with the assistance of diagnostic studies), and understanding knee anatomy (Figure 12–1), physicians are able to make the correct diagnosis and formulate an appropriate therapeutic strategy.
Functional anatomy of the knee.
The first step in the evaluation of knee pain is a thorough history that includes the core elements outlined in Table 12–1. While obtaining a history, the following key questions should be addressed:
- Has there been an acute injury?
- Is a joint effusion present?
- Is there evidence of osteoarthritis?
- Are there mechanical symptoms?
- Is there evidence of systemic disease?
Table 12–1. Knee Pain: Core Elements of the History. |Favorite Table|Download (.pdf)
Table 12–1. Knee Pain: Core Elements of the History.
- Age and sex of the patient
- Circumstances of the onset of pain
- Exacerbating and alleviating factors
- Presence of swelling and warmth
- Loss of range of motion
- Loss of function – inability to bear weight
- Presence of mechanical symptoms (locking/catching, instability)
- Duration of stiffness when arising in the morning or after inactivity
- Localization of symptoms to specific regions of the knee (ie, anterior, posterior, medial, or lateral)
- Involvement of other joints
- Presence of systemic symptoms
The answers to these questions help the clinician narrow the differential diagnosis and formulate a strategy for a directed work-up of the knee pain.
The history should also determine whether the pain is localized to a specific region of the knee, which also can be a helpful guide to the cause of symptoms. The examiner should take into account the age and sex of the patient, both of which can influence the differential diagnosis. Finally, the clinician should bear in mind that pain can be referred to the knee from other sites, most notably the ipsilateral hip. Every patient with knee pain should have a careful examination of the hip.
General Approach to the Physical Examination
The general physical examination has 5 major components: observation of stance and gait, range of motion, palpation, examination for a knee effusion, and stability tests. After completing these general examinations and considering the patient’s history, the clinician can generate a differential diagnosis and focus the work-up accordingly (see specific injuries and conditions below).
Observation of Stance and Gait
Physical examination should start with observation of stance and gait. Can the patient bear weight on the affected leg? Is there a limp? Attention should be paid to medial or lateral translation ...