lowing ACL injury, dynamic knee stability must be achieved via neuromuscular adaptations. These neuromuscular adaptation patterns, however, can differ among individuals (Hurd, Axe, & Snyder-Mackler, 2008a). Patients may report episodes of giving way (dynamic knee instability), defined as buckling or subluxation of the tibiofemoral joint since the time of initial ACL injury, result- ing in further pain and joint effusion (Fitzgerald, Axe, & Snyder- Mackler, 2000a; Fitzgerald, Axe, & Snyder-Mackler, 2000c). These episodes of knee joint instability may present as the primary contributor to decreased functional activity levels, and persistent subjective knee instability has a negative influence on outcomes, whether nonoperative or operative treatment is obtained (Meuni- er, Odensten, & Good, 2007). Knee instability is a common reason patients cite in their decision to undergo surgical reconstruction. flexed to 90° (Magee, 2002). Point tenderness should be docu- mented, along with any erythema, swelling, or bruising. Although it is not a common sequela of acute ACL injury, superficial bruising may be indicative of extra-articular ligament or tendon damage, especially to the MCL. Inspection of any quadriceps atrophy is important because quadriceps weakness can develop quickly fol- lowing ACL injury (Williams, Buchanan, Barrance, Axe, & Snyder- Mackler, 2005). Quadriceps atrophy may be more easily assessed during a quadriceps set, which also allows for assessment of qual- ity of quadriceps activation and control. Patellar joint mobility should be assessed in all directions because patellofemoral joint hypomobility can affect knee flexion and extension ROM. If previ- ous scars are present, assessing scar tissue can provide informa- tion on the patient’s typical healing processes. Gait Patients will often demonstrate an antalgic gait pattern following ACL injury. A joint stiffening strategy consisting of decreased peak knee flexion and increased co-contraction of the quadriceps and hamstrings during stance phase may be present (Chmielewski, Hurd, & Snyder-Mackler, 2005). Decreased stance time on the in- volved limb and knee extension at heel strike may also develop secondary to feelings of knee instability and pain. Increased hip joint excursion, but with decreased peak hip flexion of the in- volved limb compared to the uninvolved limb, may be observed, and is more likely to be present in women than in men (Di Stasi & Snyder-Mackler, 2012). See below for further discussion of gait patterns and their implications for neuromuscular control and os - teoarthritis development. and limited activity levels (Millett, Wickiewicz, & Warren, 2001). The incidence of ROM loss after ACL reconstruction is reported to be between 2% and 11% (Millett et al., 2001). For patients plan- ning to undergo ACL reconstruction, ROM measurements using goniometry are useful for determining the timing of surgery. The use of goniometry for measuring ROM is highly valid and reli- able both within and between examiners (Phisitkul, James, Wolf, & Amendola, 2006). Full preoperative knee extension ROM has been linked to better postsurgical outcomes (Shelbourne, Wilck- ens, Mollabashy, & DeCarlo, 1991). Mauro and colleagues re- ported that 25% of patients had knee extension deficits 1 month after ACL reconstruction, and these deficits were associated with preoperative knee extension ROM, time from injury to surgery, and use of autograft (Mauro, Irrgang, Williams, & Harner, 2008). Chronic loss of ROM can lead to higher risk of future osteoarthritis at the knee joint (Shelbourne, Freeman, & Gray, 2012). Knee joint effusion Joint effusion is an elevated level of fluid within the joint cap- sule that is often present following ACL injury and reconstruction and contributes to impairments in ROM and to pain. It had been thought that knee joint effusion led to inhibition of the quadriceps muscle (Palmieri-Smith, Kreinbrink, Ashton-Miller, & Wojtys, 2007; Spencer, Hayes, & Alexander, 1984). However, recent literature suggests that quadriceps activation failure following ACL injury may not be the result of knee joint effusion alone (Lynch et al.,
as effusion developing 8 to 24 hours following injury results from synovial swelling (Magee, 2002). Knowing the time of onset of knee effusion may provide valuable information in the diagnostic process. For example, unlike ACL injuries, meniscal injuries often do not demonstrate immediate bloody effusion, because of the mostly avascular nature of the menisci (Magee, 2002). Knee joint effusion levels may reflect the irritability of the joint and can in- crease following physical activity, especially when knee instability is present. Monitoring joint effusion is thus useful in determining the correct progression of therapeutic exercises and activity, and it can be an indicator of patient progress (Sturgill et al., 2009). The loss of static and dynamic stability following ACL injury may lead to patient reports of knee instability with activity levels as simple as walking. When ligamentous support is diminished fol- Physical examination The physical examination strategy and procedures are directed by the information the clinician collects during the subjective in- terview and history. The clinician will use this information to col - lect data during the physical examination to confirm the correct hypothesis and reject nonviable ones (Rothstein, Echternach, & Riddle, 2003). Observation and palpation In addition to a thorough patient history, a physical examination that includes observation and palpation can provide further infor- mation for formulating an accurate diagnosis. Posture should be assessed in both the seated and standing positions, and any de- viations from normal posture that could affect the function of the knee should be noted, including excessive thoracic kyphosis or lumbar lordosis, pelvic obliquities, femoral or tibial torsion, genu valgum or varum, genu recurvatum, abnormal patellar position- ing, and excessive foot pronation. Posture should likewise be as- sessed during movements such as squatting or stair climbing to determine if these deviations are present during dynamic activi- ties, or if additional postural deviations are presented that were not observed during static postural assessment. For example, the patella may be positioned normally in a static standing position, but normal superior migration of the patella may be decreased during an activity involving knee flexion, which could indicate possible patellofemoral joint hypomobility. Palpation and inspection of the knee joint and surrounding struc- tures can further assist in the diagnostic process. Most structures can be easily palpated with the knee in an extended position, al- though the medial and joint lines are best palpated with the knee Clinical tests When evaluating a patient with ACL injury over an episode of care, clinicians should use assessments of impairment of body structure and function, including measures of knee joint ROM, knee effusion, knee laxity/stability, thigh muscle strength, lower limb movement coordination, and other performance-based measures (Logerstedt et al., 2017). Knee range of motion Acute loss of knee flexion and/or extension ROM may be present secondary to increased pain and joint effusion after ACL injury and ACL reconstruction. Regaining full knee ROM following ACL injury or reconstruction is crucial because chronic loss of as little as 3° of extension ROM can lead to significant impact on both subjective and objective patient outcomes after injury and recon- struction (Shelbourne & Gray, 2009). Full knee joint ROM can be difficult to define secondary to large population variance. Magee describes full knee flexion as equal to 135° and knee extension as equal to 0°; however, hyperextension up to 15° is recognized as common, especially in women (Magee, 2002). Shelbourne and colleagues (2012) recommend comparing the involved knee joint ROM to the uninvolved knee in order to determine “normal” mo- tion for each individual patient. The International Knee Documen - tation Committee (IKDC) criteria for normal knee ROM are knee extension within 2° and knee flexion within 5° of the contralateral knee (AOSSM, 2009). Knee ROM is important to monitor because a change can lead to altered biomechanics with functional tasks
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