History and Examination for Knee Pain
The history may be that of pain accompanying weight bearing activities, morning stiffness lasting usually less than 30 minutes, and episodes of knee buckling. Because knee pain is often associated with the patellofemoral joint, activities such as climbing stairs involving bending of the knee can be difficult or painful. Assessment should include valgus or varus malalignment which would predict radiographic compartmental OA and gait analysis to assess for a limp or slow gait.
Weight bearing radiographs are the preferred imaging for the diagnosis of OA while MRI is useful in diagnosing meniscal tears or mechanical symptoms. Specific orthopaedic tests for knee conditions are listed below.
The patient lies in the supine position with the knee completely flexed (the heel to the buttock). The examiner then medially rotates the tibia. If there is a loose fragment of the medial meniscus, this action causes a snap or click that is often accompanied by pain. By repeatedly changing the amount of flexion, the examiner can test the entire posterior aspect of the meniscus. The anterior half of the meniscus is not as easily tested because the pressure on the meniscus is not as great. To test the medial meniscus, the examiner performs the same procedure with the knee laterally rotated.
Anterior and posterior drawer tests
The drawer sign is a test for one plane anterior and one plane posterior instabilities. The difficulty with this test is determining the neutral starting position if the ligaments have been injured. The patient’s knee is flexed to 90°, and the hip is flexed to 45°. In this position, the anterior cruciate ligament is almost parallel with the tibial plateau. The patient’s foot is held on the table by the examiner’s body with the examiner sitting on the patient’s forefoot and the foot in neutral position. The examiner’s hands are placed around the tibia and it is drawn forward on the femur. The normal amount of movement that should be present is around 6mm. If however the tibia moves forward more than 6mm. The anterior cruciate ligament may have been injured by some degree. The posterior cruciate ligament may also be tested in a similar fashion except this time the tibia is pushed posteriorly with respect to the femur.
Medial and lateral collateral ligament stress testing
The valgus test is an assessment for one-plane medial instability, which means that the tibia moves away from the femur i.e. gaps on the medial side. The examiner applies a valgus stress (pushes the knee medially) at the knee while the ankle is stabilised in slight lateral rotation either with the hand or with the leg held between the examiner’s arm and trunk. The knee is first in full extension and then slightly flexed so that it is unlocked (20° to 30°). If the test is positive (i.e. the tibia moves away from the femur an excessive amount when a valgus stress is applied) when the knee is in extension, the Medial collateral ligament may have been injured to some degree. If a varus stress is then applied in the same fashion, the integrity of the lateral collateral ligament may be similarly tested.
Below is a table of commonly encountered knee conditions (see Table 5) that should be considered in the differential diagnosis of knee OA and the features that distinguish these conditions from OA.
|Conditions||Features according to history||Features on physical examination||Laboratory and radiographic features|
|Chronic inflammatory arthritis including rheumatoid arthritis||Prominent morning stiffness, other joints affected (symmetrically)||Other joints swollen or tender, hand deformities||Increased ESR, inflammatory synovial fluid, erosions on radiographs|
|Gout or pseudogout (chondrocalcinosis, CPPD)||Other joints affected, especially great toe (for gout), wrists or shoulders (pseudogout)||Other joints swollen or tender.||Inflammatory synovial fluid containing crystals, radiographs may show chondrocalcific lime (CPPD)|
|Hip arthritis||Groin, trochanteric or buttock pain, or only anterior knee pain in some cases||Pain with hip flexion and internal rotation; Trendelenburg lurch tenderness||Abnormal hip radiograph|
|Chondromalacia patella||Onset at relatively young age; predominance of anterior knee symptoms (pain with kneeling, stairs, squatting)||Tenderness only over patellofemoral joint, pain with patella pressure (inhibition, grind tests)||Normal radiograph or mild patella irregularity on sunrise view.|
|Anserine bursitis||Anteromedial knee pain||Tenderness distal to knee over medial tibia||Normal radiograph|
|Trochanteric bursitis||Lateral hip pain, especially at night||Tenderness in region of lateral hip||Normal radiograph|
|Iliotibial band syndrome||Lateral thigh pain, extending to lateral knee||Tenderness and tightness of the iliotibial band||Normal radiograph|
|Meniscal tear||Prominent mechanical symptom(e.g. locking or buckling)||Tenderness over joint line; positive on McMurray test||Meniscal tear on MRI, radiographs normal.|
|Joint tumors||Nocturnal or continuous pain||Bloody synovial fluid and possibly abnormality on X-ray|
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