Joint range of motion Evaluating joint range of motion should be part of the standard evaluation for individuals with knee OA. Loss of full extension at the knee is an important indicator of symptomatic progression. In a sample of individuals with knee OA, knee flexion contractures of any amount were predictive of future need for total knee replacement (Zeni, Axe, & Snyder-Mackler, 2010). Therefore, making sure patients achieve and can maintain normal range of motion is important to prevent future disability. When testing range of motion, it is important to document the patient position. There are many multiarticular muscles in the lower extremity, and changing the position of the hip, knee, or ankle during testing may change the individual’s range of motion. It also should be documented whether the range of motion was active or passive. Because patients with knee OA often have substantial pain, they may have substantial active range of motion deficits, even if they have normal passive ranges. Frontal plane joint position Because the knee position in the frontal plane can change the magnitude of the adduction moment, a severe varus or valgus position may increase the risk of OA progression. Individuals with a varus knee are more likely to develop OA in the medial tibiofemoral compartment, whereas individuals with a valgus knee are more likely to develop lateral compartment OA. Measuring the joint position in the frontal plane will help make informed decisions about whether or not bracing may be appropriate for the patient. Alignment can be measured using a variety of methods. The gold standard for lower extremity structural alignment in the frontal plane is done using long leg X-rays, where the position of the femur can be compared to the position of the tibia. In a clinical setting, the therapist can use the quadriceps angle (Q-angle) to ascertain a relative lower extremity position. This measure estimates the line of force of the quadriceps muscle, which is driven by the underlying bony structure. To measure this angle, the clinician should place the patient in a supine position. The hip and knee should be extended, and the hip should not be rotated internally or externally. The center of the goniometer should be placed over the anterior patella, with the proximal arm aligning with the anterior superior iliac spine (ASIS) and the distal arm aligning with the tibial tuberosity (Figure 7). The angle is recorded, along with a descriptor of varus or valgus to differentiate the direction of the alignment. There are alternate positions for this test, including standing, which will account for the effect of weight bearing on lower extremity alignment. Figure 7: Q-Angle Measurement
the clinical diagnosis of knee OA that was discussed previously in this course. Pain frequency can be assessed by asking the patient whether the pain is intermittent or constant, although both are implicated in poor function in patients with knee OA (Davison, Ioannidis, Maly, Adachi, & Beattie, 2016). It also can be assessed by asking the number of days in the past week in which the patient had pain or by asking whether the patient had pain most days of the month. There are also knee-specific questionnaires that can be used to measure aspects of a patient’s pain. The Intermittent and Constant Osteoarthritis Pain (ICOAP) scale is a questionnaire that asks questions about constant pain, as well as pain that “comes and goes.” This questionnaire recently has been shown to be responsive and reliable for patients with knee OA, and it may offer a more comprehensive and objective evaluation of how different types of pain associated with knee OA impact function and quality of life (Turner, Moreton, Walsh, & Lincoln, 2017). Instability Joint instability is a common complaint among individuals with knee OA. Even without pain, patients may complain that functional activities such as descending stairs are difficult because of knee joint instability. Instability is a general term, but is often thought of as the result of laxity within the knee joint (a structural issue) or poor muscular control during dynamic activities (a neuromuscular issue). It is likely a combination of the two, as changes to the structure may affect the afferent feedback system to the central nervous system, which in turn cannot produce the required motor output. Instability may be described as “knee buckling” by patients, which can arise as a result of muscle weakness, particularly of the knee extensors. Reducing instability through bracing or neuromuscular retraining can have a positive impact on outcomes and may benefit the joint structure. Recent experimental studies in rat models of knee OA have revealed that controlling instability delays degeneration of the knee cartilage (Murata et al., 2017), although these results have not been shown in humans. The presence of instability can be ascertained through patient self-report by asking “Have you had any episodes of knee buckling?” Other measures of instability, such as joint laxity and thrust gait, can be assessed through physical examination and observational gait analysis. Laxity Laxity of the knee joint can be evaluated through manual assessment of the arthrokinematic motions in the frontal and sagittal planes. As the cartilage becomes thinner, the ligaments and joint capsule surrounding the knee joint become loose. This may allow excessive “play” within the joint, which may contribute to abnormal frontal plane knee motions during walking. To date, there is inconclusive evidence as to whether joint laxity is related to the incidence or progression of knee OA, and prospective studies in this area are needed (Freisinger, Schmitt, Wanamaker, Siston, & Chaudhari, 2016). Frontal plane thrust gait Thrust gait is a term given to individuals who present with a rapid motion into knee varus or valgus when walking. It typically occurs as the individual transitions to the single limb stance portion of the gait cycle and full body weight is placed on the affected limb. Varus thrust appears as an apparent increase in the varus angle, or worsening of leg-bowing, during single limb stance. Valgus thrust is the opposite. Thrust gait has traditionally been assessed through a visual assessment of the patient’s gait, although the presence of this thrust has been substantiated using three-dimensional motion analysis techniques (Sosdian et al., 2016). The presence or absence of thrust gait should be considered when evaluating individuals with knee OA, as stabilizing braces may offer more normal gait dynamics for individuals with a positive thrust. Effusion Joint swelling and irritation to the joint capsule can be one cause of joint pain, abnormal motor control, or muscle inhibition. Effusion, or swelling within the joint, is a consistent feature
Note. From Western Schools, 2018.
Pain Knee OA is a chronic condition that is characterized by mild to severe joint pain; therefore, assessing pain is a key component of any evaluation. The magnitude of pain can be evaluated using visual analog scales or numeric pain ratings that range from 0 to 10; however, there are other dimensions of pain that may provide valuable insight into the patient’s rehabilitation potential and appropriate interventions. One common additional domain of pain is pain frequency. Pain frequency is one component of
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Book Code: PTNC1023
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