Knee Diagnosis and Decision Making

For the experienced practitioner, the history and physical examination remains the most efficient, sensitive, specific, accurate, and cost-effective method of establishing a diagnosis in patients with knee-related complaints. Several investigators have demonstrated that the history and physical examination have equivalent sensitivity and specificity to magnetic resonance imaging (MRI) for a variety of intraarticular pathologies, with an overall accuracy of 93%. When taking a systematic approach to patients with knee-related concerns, assessing each structure in question sequentially for possible injury is critical. Developing an intuitive and comprehensive approach to the physical examination requires a detailed understanding of knee anatomy, in particular the relation of the surface skin to the underlying structures, to be able to relate tenderness to pathology. A complete description of the relevant anatomy is described in Chapter 91 . In-depth knowledge of knee pathology can be helpful so that the history and examination can be dynamically tailored; pertinent clinical conditions are described in Chapter 95, Chapter 96, Chapter 97, Chapter 98, Chapter 99, Chapter 100, Chapter 101, Chapter 102, Chapter 103, Chapter 104, Chapter 105, Chapter 106, Chapter 107, Chapter 108 .


Eliciting the history starts with the chief or primary complaint that leads the patient to present for an evaluation. We endeavor to record this complaint in the patient’s own words, because they provide the first clues regarding the patient’s reason for the office visit. Asking an open-ended question such as, “What brings you to the office today?” is very helpful. Giving patients the opportunity to “tell their story” also allows them to develop a more significant and meaningful relationship with their physician.

Once the patient has completed his or her initial response, the surgeon can return to the beginning of the story as necessary to fill in gaps and collect more details. In particular, the examiner must determine the duration of the complaint and the date of onset. Important details often can be gathered from the patient’s recollection of the inciting event or trauma, should one exist. If the injury occurred during an athletic endeavor, the examiner should obtain a full account of the event, including whether this incident was a contact or noncontact injury and if it occurred during practice or during a competition. These details may provide the first clues as to the underlying pathology. For instance, a valgus stress suggests an injury to the medial collateral ligament (MCL), whereas a high-energy trauma such as a motorcycle accident may suggest a knee dislocation or multiligamentous injury. In comparison, noncontact ACL injuries usually occur in the context of stopping quickly, cutting sharply, and landing and changing direction with the foot planted. The mechanism of ACL injury in skiers is different—when skiers injure the ACL, they are moving out of control with the knee bent or extended. The uphill arm is back, the body is off balance, the hips are lower than the knees, and the weight is placed on the inside edge of the downhill ski. This mechanism of injury has been referred to as the “phantom foot” mechanism. Recollection of an auditory pop or a tearing sensation may be present. Up to 66% of patients with an ACL injury describe such a sensation. Swelling immediately after the event may also occur. Indeed, a hemarthrosis develops in most persons with ACL injuries within 3 hours of the initial tear ( Table 92-1 ).

TABLE 92-1


Traumatic Atraumatic
Anterior cruciate ligament tear
Posterior cruciate ligament injury
Chondral fracture
Patellar dislocation
Meniscal tear
Intraarticular fracture
Tear in the deep portion of the joint capsule
Pigmented villonodular synovitis
Sickle cell anemia
Charcot arthropathy
Pharmacologic coagulopathy

If no specific event can be recalled, the patient should be asked if he or she has had a recent change in activity, which might suggest overuse. Commonly patients may have changed training techniques (e.g., increased frequency, increased distances, or a change in terrain or surfaces). A recent increase in running may suggest a stress fracture or patellofemoral syndrome. Acute changes from inactivity to activity may lead deconditioned patients to subject their knees to nonphysiologic kinetics as a result of loss of neuromuscular control.

The major symptoms on which to focus for a patient presenting with knee-related concerns include (1) pain, (2) instability, (3) mechanical symptoms, (4) stiffness, and (5) swelling. The patient should be asked about the continued presence of pain and any change in character or severity of the pain. Use of visual analog scales can be helpful. Pain ratings based on a 0 to 10 scale can be used. It is helpful to hear whether the pain is constant, is only related to activities, or occurs after activity. Pain related to stair climbing or prolonged sitting suggests a patellofemoral etiology, whereas pain with twisting or rotating activities (e.g., rolling over in bed or getting out of a car) is suggestive of meniscal pathology.

Subjective instability should be explored, with attention paid to determining the frequency and inciting events or activities surrounding each instability event. For example, patients with an ACL tear often state that they experience instability with pivoting, twisting, or cutting activities. They may also describe a sensation of movement with their knees that they often explain by placing two fists together and moving one with respect to the other in what has been called the two-fist sign . In contrast, instability that is experienced linearly, as in walking on level ground or on stairs, is often associated with quadriceps weakness and deconditioning. Side-to-side instability on level ground may suggest valgus or varus laxity, whereas instability when descending a ramp may also be experienced by patients with damage to the posterolateral corner (PLC).

The patient should be asked about any evaluation or treatment he or she received at the time of the injury or subsequent to the injury. It may also be helpful to know if weight-bearing restrictions were recommended. Knowledge of previous immobilization is also helpful, particularly if the patient has residual loss of range of motion. For any patient with a prior surgical intervention, the operative report and arthroscopy images can provide valuable information. Finally, the physician should ask which, if any, of these treatments have benefited the patient. These questions help guide the surgeon in creating a treatment plan that avoids replication of prior failed treatments.

Once the history surrounding the present complaint is fully understood, the physician should collect general medical, surgical, and social histories. For athletes, a more complete understanding of their athletic history should be sought, including their current and past level of play, the number of hours per week that they play, and their skill level, potential, and athletic goals. These factors all play a role in surgical decision making. In particular, in the patient with an ACL tear who plans to return to category I hard cutting or pivoting sports such as basketball, football, rugby, volleyball, or mogul/black diamond skiing, the risk for reinjury with nonoperative treatment of an ACL tear is high. The surgeon should also obtain an occupational history, because a patient who is reliant upon the injured extremity for his or her livelihood likely requires a more aggressive treatment regimen.

A review of systems should always be collected as well. A particular focus should be placed on pain and swelling in other joints, eye disease, back pain, pain with urination, and skin disorders, all of which may hint at a diagnosis of an inflammatory arthropathy. Similarly, a history of fevers, night sweats, or drainage may lead the physician to suspect infection. A history of atraumatic knee pain with an associated mass with primarily nocturnal or constant pain may lead the physician to a neoplastic diagnosis. Pain out of proportion, hypersensitivity, and color and/or temperature changes to the knee should lead the physician to suspect a complex regional pain syndrome.

Finally, the physician must discuss goals and expectations with the patient. Expectations frequently need to be tempered. In athletes and former athletes presenting with a knee injury, it behooves the surgeon to come to a better understanding of whether the athlete would like to return to play or simply desires a painless knee for activities of daily living. The patient is most likely to achieve a successful result if he or she understands the goals of the treatment program for the presumed diagnosis.

Physical Examination

Physical examination of the knee requires an in-depth understanding of the anatomic structures and the function of these structures, because each provocative test seeks to isolate the function of each structure. We often view the examination as a multistep process: (1) inspection, (2) palpation, (3) range of motion and strength testing, (4) patellar testing, (5) meniscal testing, (6) ligamentous stability testing, (7) gait assessment, (8) evaluation of muscle weakness and imbalance (e.g., hamstring tightness, quadriceps tightness, or core weakness), and (9) assessment of the back, hip, and feet. We start by examining the noninjured extremity, which may provide important information regarding baseline abnormalities and also helps to relax the patient.


A great deal of information can be gained from inspection of the patient before taking a history or performing a focused physical examination ( Box 92-1 ). If possible, patients should be observed as they enter the examination room or at some other time when they do not know they are being observed. Once the patient is in the examination room, the physician can gain insight into the patient’s general mobility by observing him or her transfer from a chair to the examination table.

Box 92-1

Diagnosis by Visualization

  • Atrophy

  • Effusion

  • Ecchymosis

  • Malalignment

  • Gait abnormalities

  • Extensor mechanism disruption

The periarticular skin should be carefully inspected for (1) any surgical scars, which may affect future surgical planning; (2) erythema, which should be demarcated with a skin-marking pen if it is believed to reflect an underlying cellulitis; (3) ecchymoses, which reflect subcutaneous hemorrhage that may signal a capsular injury ( Fig. 92-1 ); and (4) abrasions, which may provide a clue to the direction of the primary trauma. In particular, an anterior tibial abrasion is classically associated with a posterior cruciate ligament (PCL) injury because of the posteriorly directed force on the anterior tibia at the time of injury ( Fig. 92-2 ). Attention should be directed to the presence or absence of effusion, any localized swelling, and muscle tone within the periarticular muscles, in particular the quadriceps and vastus medialis obliquus. The examiner should examine a patient with a suspected dislocation for the presence of any abnormal skin furrows or dimpling, which could signal buttonholing of the condyles through the capsule and the need for open reduction. Although general inspection may reveal atrophy, the most sensitive measurement of atrophy is a comparison of thigh circumference with the contralateral knee ( Fig. 92-3 ). This measurement can be used as a marker for the rehabilitation process after surgery. General inspection may reveal stigmata of other general medical conditions, such as signs of venous stasis, ulcerations, or prior amputations as a result of diabetic neuropathy or vascular insufficiency, as well as signs of chronic infections or abscesses. Predrawn knee schematics may be helpful for recording findings from visual inspection. Alternatively, obtaining a photograph at the time of presentation can be invaluable for comparison at a later date. Photographs can be entered into the electronic medical record. Serial examinations can be crucial for the determination of progression, especially in the acutely injured patient.


Ecchymoses reflect a subcutaneous hemorrhage and may signal a capsular injury. These posterolateral hemorrhages raise suspicion for a posterolateral corner ligamentous injury.


An anterior tibial abrasion is shown with associated posterior subluxation of the tibia, suggesting a posterior cruciate ligament injury.


Thigh circumference, which the examiner should always measure at the same distance proximal to the superior patellar pole, is a sensitive measure of quadriceps atrophy.

Patients should remove their shoes so that the entire limb can be inspected. Overall limb alignment should be visually estimated within the coronal, sagittal, and axial planes. Any deformity should be fully inspected visually and radiographically. Specific attention should be directed to malrotation. With the patient supine, the examiner should also visually inspect the height level of the patella for alta or baja. The physician may also want to measure limb length. Although the most accurate method for limb length measurement is the placement of sized standing blocks under the short leg until the pelvis is level, a rapid, rough estimation can be gained with a glance at the relative heights of the medial malleoli in the supine patient. The physician can also estimate the Q angle visually and measure it with a goniometer, although this measurement can be affected by a variety of other deformities. Deformities within the foot should also be observed. For instance, pes planus may be a contributing factor to genu valgum or may be a sign of generalized ligamentous laxity. Core strength can also be observed by asking patients to stand on one leg. An inability to maintain a level pelvis indicates weakness of the core trunk stabilizers that can indirectly contribute to patellofemoral symptoms.

The patient’s gait should be observed. Although gait is a complex process requiring normal function of the foot, ankle, knee, hip, and lumbosacral spine, some gait abnormalities can also be referred to the knee. One should observe for varus and valgus thrusts, an antalgic gait with shortening of the stance phase for the affected limb, and the foot progression angle. Patients with ACL deficiency may exhibit a quadriceps avoidance gait, possibly to prevent excess anterior tibial translation.


It should be noted that many patients in the acute postinjury phase have generalized inflammation with diffuse tenderness that tends to be nondiagnostic; as a result, the patient may need to return at a later date for a repeat examination.

The knee should be palpated for the presence or absence of an effusion. The examiner can milk fluid down from the suprapatellar bursa while holding the patella between the thumb and forefinger of the contralateral hand to assess for the ability to ballot the patella. Alternatively, the examiner can feel for swelling at the soft spots medial and lateral to the patellar tendon, where the capsule is fairly subcutaneous. The other area where the surgeon may be able to palpate synovial fluid is in a Baker cyst, which is most commonly posteromedial between the semimembranosus and the medial head of the gastrocnemius.

The quadriceps tendon and its patellar insertion can be palpated both for tenderness associated with quadriceps tendonitis and a gap associated with a quadriceps tendon tear. The patella should be palpated for prepatellar tenderness or fullness that may be a sign of prepatellar bursitis. The patellar tendon and its patellar origin should be palpated for tenderness associated with patellar tendonitis ( Fig. 92-4 ), as well as for a gap associated with a patellar tendon tear. The tibial tubercle should be palpated ( Fig. 92-5 ) for bony tenderness, which may be associated with Osgood-Schlatter syndrome.


Tenderness at the inferior pole of the patella suggests patellar tendonitis.


Tenderness to palpation at the tibial tubercle suggests Osgood-Schlatter syndrome, fracture of the tibial tubercle, or possibly insertional patellar tendonitis.

On the medial side of the knee, the entire course of the medial collateral ligament should be palpated for tenderness. The femoral and patellar attachments of the medial patellofemoral ligament should be evaluated for a palpable gap or tenderness. The medial tibial plateau should be palpated for tenderness because it might be associated with an acute fracture or stress fracture. The region just anteromedial to the patella should be assessed for a palpable tender band from plica syndrome ( Fig. 92-6 ). The distal insertion of the sartorius, semitendinosus, and gracilis tendons should be palpated for pes anserine bursitis. The posteromedial joint line should also be palpated for a possible meniscal tear. Whereas anteromedial ( Fig. 92-7 ) and medial joint line tenderness is often associated with plica syndrome or hypertrophic fat pad syndrome, displaced bucket hand meniscal tears characteristically have more tenderness anterior than the classic posteromedial location associated with most meniscal tears.


A tender palpable band, which may snap back and forth over the medial femoral condyle, suggests medial plica syndrome.


Palpation for tenderness at the anterior medial joint line.

Similarly, the surgeon must also palpate the lateral structures. The lateral collateral ligament is best identified with the knee in the “figure of four” position, where varus stress makes the ligament taut and more easily palpable. The other structures of the PLC, such as the popliteus tendon and the popliteofibular ligament, can be more difficult to assess with palpation. The biceps tendon is most easily assessed as a cord at the posterolateral surface of the fibular head. Just anterior to the biceps tendon is the iliotibial band, which can be palpated as it passes over the lateral femoral condyle and at its tibial attachment at Gerdy’s tubercle. The fibular head should also be assessed. The lateral tibial plateau should be palpated for tenderness, which might be associated with an acute fracture or stress fracture. The posterolateral joint line ( Fig. 92-8 ) is palpated for a possible meniscal tear. As on the medial side, anterolateral joint line tenderness can be associated with hypertrophic fat pad syndrome or a displaced bucket handle tear. Just distal to the fibular head, the examiner can commonly palpate the common peroneal nerve. In patients with suspected pathology of the peroneal nerve, the examiner should attempt to elicit a Tinel sign. Pain associated with common peroneal neuritis may be referred to the anterolateral proximal tibial region.


Palpation for tenderness at the posterior lateral joint line.

Range of Motion and Strength Testing

Range of motion is a fairly sensitive predictor of intraarticular pathology and is critical for knee function. Normal knee range of motion has been described as 0 to 120 degrees, although the range of motion actively used for gait is 10 to 120 degrees. However, considerable variation exists. At terminal extension many persons have up to 5 degrees of hyperextension, which, in combination with range from 0 to 10 degrees of flexion, may be useful for the “screw home” mechanism of internal rotation that tensions the cruciate ligaments and “locks” the knee at full extension. Many persons have additional passive flexion beyond their active range; in men this is commonly 140 degrees and in women it is 143 degrees, although in societies where kneeling is common, such as in Japan, India, and the Middle East, passive flexion to 165 degrees is common. One hundred twenty-five degrees of flexion are necessary to squat, whereas 110 degrees of flexion is required to descend stairs in normal fashion. The loss of as little as 10 degrees of flexion will affect running speed. The loss of as little as 5 degrees of extension can cause a limp with increased quadriceps activation during gait and resultant quadriceps strain and fatigue, as well as patellofemoral pain. Differences between passive and active range of motion should be noted. A loss of both is considered a “contracture” and implies a block to motion, whereas a loss of active range of motion with preserved passive range of motion is considered a “lag” and implies a muscle tightness or imbalance.

Several methods may be used to test range of motion. A goniometer can be placed on the lateral side of the knee with the proximal end pointed toward the greater trochanter and the distal end pointed toward the lateral malleolus. This method has high inter- and intraobserver reliability. A more sensitive indicator of full extension and flexion is the measurement of the heel-height difference with the patient placed in the prone position ( Fig. 92-9 ). Similarly, the heel-buttock distance can be measured in full flexion in the supine position. One centimeter correlates with approximately 1 degree.


The most sensitive way to measure extension deficit is to measure the heel-height distance difference with the patient in the prone position. A 1-cm difference roughly correlates with a 1-degree difference.

Range of motion testing should also be performed on the ankle and hip joints and lumbar spine. We also commonly test for generalized ligamentous laxity, specifically by examining for elbow recurvatum, hyperextension at the metacarpophalangeal joint, the ability to abduct the thumb to meet the forearm, and excess external rotation of the humerus in adduction, all of which may signal a connective tissue abnormality. It should be noted that some confusion exists in the literature regarding the terms laxity and instability . Laxity is a term used to describe a finding on physical examination, whereas instability is a term used to describe a patient’s subjective experience of this same entity. It is possible for a person to have generalized ligamentous laxity with no instability, and vice versa.

Several other structures can be assessed during range of motion testing. For instance, if the patient reports lateral knee pain with a palpable snap, the examiner can flex the knee, internally rotate, and then extend the knee to elicit snapping of the biceps tendon over a prominent fibula head ( Fig. 92-10 ). This observation may not be detected with external or neutral tibial rotation. It is important to consider this entity because it can mimic an unstable lateral meniscal tear. More commonly, the patient should be assessed for hamstring tightness in the supine position with the examiner attempting to flex the hip with the knee extended. We grade hamstring flexibility in degrees from the examination table. In this same position, the patient should be assessed for the ability to perform a straight leg raise. The examiner may also wish to assess for iliotibial band tightness using the Ober test. In this test, the patient is placed in the lateral decubitus position with both hips and knees flexed to 90 degrees so as not to flatten the lumbar spine. Concomitantly, the affected leg is abducted to 40 degrees and fully extended, and an attempt is then made to adduct the hip. An inability to adduct past midline signifies an iliotibial band contracture ( Fig. 92-11 ).

Feb 25, 2019 | Posted by in SPORT MEDICINE | Comments Off on Knee Diagnosis and Decision Making
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