Knee pain is perhaps one of the most difficult conditions to diagnose in any joint. It is a challenge for the joint surgeon to determine the cause of knee pain because it involves not only intra-articular lesions but also a variety of extra-articular factors. Because more than half of all knee pains are not caused by intra-articular lesions, it is particularly important to perform a detailed preoperative history and systematic physical examination to determine the cause of the joint pain.
Medical history
Taking a detailed preoperative history is an important step in the diagnosis of any disease. Symptoms arising from the knee area are often nonspecific. Symptoms such as pain, beaten tender legs, and joint interlocking can be caused by either cruciate ligament or meniscal injuries, or by patellofemoral abnormalities, articular cartilage lesions, or even by mere ingrowth of an abnormal hyperplastic synovium. In addition, because extra-articular causes of knee pain can cause or manifest as knee pain, attention should be paid to the questioning of extra-articular symptoms, such as the low back, which may cause posterior knee pain, and the hip, which may cause medial knee symptoms, etc.
The cause of knee symptoms is often suggestive. Traumatic causes often imply damage to the internal and external stabilizing structures of the joint and other intra-articular structures, strain causes often suggest muscle-tendon stop disease, and degenerative causes are even more revealing. Meniscal injuries are also often associated with rotational activity of the knee.
The time of onset or injury is also important in the diagnosis of knee pain. Meniscal injuries have typical signs and symptoms in the acute phase, but after they become old, there may be only a sensation of a tender leg and intra-articular foreign body entrapment, making the diagnosis difficult; ACL injuries may have only a sensation of joint instability in the early stages, and when more complex pain develops, it indicates further damage to the articular cartilage, meniscus, and ancillary joint stabilizing structures; mild posterior cruciate ligament injuries In the early stages, there is usually no specific discomfort due to quadriceps compensation, but when anterior knee pain occurs it often indicates severe degeneration of the patellofemoral joint. In addition, the time of onset or injury is of great importance in determining the treatment plan for knee disorders. Whether the injured meniscus should be repaired and the ease of repair can be assessed depending on the time of injury; acute ACL injuries with medial collateral ligament injuries should be treated conservatively, and ACL reconstruction can be performed after the healing period of the medial collateral ligament; acute ACL or posterior cruciate ligament injuries with posterior lateral horn injuries should be repaired or reconstructed as soon as possible for all damaged ligament structures. reconstruction.
Physical Examination
The physical examination of the knee is complex, and there may be different methods of examination for a single injury or lesion. Rather than listing the various methods, we will describe the most commonly used physical examinations that we believe have the most diagnostic value and analyze their specific procedures and implications. It is very important for knee surgeons to develop their own set of more systematic testing procedures in their daily practice.
I. Knee joint force line – standing position
Stand flat with shoes off and bring the ankle and knee joints together as much as possible to understand the knee axis.
The anatomic axis (FTA) of the normal knee has a 5°-7° valgus angle, while the mechanical axis is 0°, meaning that the center of the femoral head, the center of the knee joint and the center of the ankle joint are in a straight line. In a general physical examination, the mechanical axis of the knee is primarily understood in general terms. Normally the knees are able to come together and there should be 4-150 px between the ankles. If the knees are not able to come together it means that the knees are inversion, if the ankles are too far apart it means that the knees are ectropion, and the inversion angle is estimated by visual inspection.
The determination of the knee joint force line is important for the diagnosis of joint pain and the selection of surgical options. An inversion knee with medial knee pain is often, and an ectropion knee with lateral knee pain is often indicative of osteoarthritis of the medial or lateral tibiofemoral joint. The presence of lateral knee pain in the internally turned knee often indicates damage to the lateral meniscus of the knee, while the presence of medial knee pain in the externally turned knee often indicates damage to the medial meniscus of the knee. The medial meniscus should be removed cautiously as it can exacerbate the degeneration of the medial inter-articular compartment. Removal of the lateral disc meniscus can result in a mild correction of the inversion force line, which facilitates the redistribution of stresses between the internal and external joint spaces, and thus good results can sometimes be obtained after removal of the lateral meniscus. In contrast, Westerners have more valgus knees and place much more emphasis on the lateral meniscus than we do, and the damaged lateral meniscus is the object of every effort to repair, although of course, there is also the factor that the lateral tibiofemoral joint is less anastomosed than the medial and that the lateral meniscus has a greater role in reducing punctate stress contact in the tibiofemoral joint. In osteoarthritis with severe knee force line abnormalities, arthroscopic debridement and chondral treatment can relieve knee pain, although the primary treatment should be a high tibiofemoral osteotomy.
II. Patellofemoral-related examination – supine position
The patella is both a fulcrum for quadriceps stress transmission and a “buoy” in the front of the knee joint.
Patella-related examination mainly involves the patellofemoral joint, medial synovial crease and joint effusion.
1. Joint effusion: The patient is examined in the supine, extended knee position. Knee effusion can be divided into three grades. Knee effusion degree three (++++) – that is, the commonly known floating patella sign: one hand on the suprapatellar capsule pressure, the other hand backward click patella, patella and femur impingement is positive, at this time there is about 60ml-80ml of fluid in the joint. Knee effusion second degree (++): when the floating patella sign is negative, the thumb and index finger of one hand are placed at the “knee eyes” on both sides of the patellar ligament, and the other hand is pressed on the suprapatellar capsule, if the thumb and index finger are opened due to the intra-articular pressure, it is positive. At this time, 30ml-40ml of joint fluid is not enough to float the patella. This method is also used to identify joint effusion and synovial hyperplasia, where the synovial hyperplasia is bilaterally elevated at the knee eyes, but when pressure is applied to the suprapatellar bursa, there is no such hydraulic transmission that causes the thumb to open. Knee effusion degree 1 (+): For a negative knee joint degree 2 examination, apply pressure with one cross finger along the lateral patellar support band and check for a sensation of hydraulic transmission or fluctuation with the index finger of the other hand at the medial patellar support band.
The joint effusion caused by acute trauma implies joint hematoma; the joint effusion caused by old injury often indicates that the tissue structure damage in the joint has not been repaired; the joint effusion without obvious traumatic causes is often a reflection of systemic diseases in the joint area, such as rheumatic fever, or it may be caused by the synovial membrane irritation by joint degeneration materials.
2, post-patellar impingement pain: bend the knee 30°-45°, squeeze the patella backward with the thumb, causing pain is positive. The purpose of the posterior patellar impingement pain test is to understand the damage or degeneration of patellofemoral cartilage, but for one thing, the positive rate of the test is not high, and for patellar cartilage chondromalacia is far less sensitive than the knee extension resistance test and the half squat test, and for another, it is impossible to distinguish between patellar cartilage chondromalacia and anterior knee pain caused by patellar subluxation. Theoretically, patellar subluxation causes high pressure and degeneration of the lateral articular cartilage of the patellofemoral joint, which should lead to lateral retropatellar impingement pain, but most patients tend to have medial retropatellar impingement pain at the same time, because the nutrition of the cartilage is completed during the extrusion and expansion caused by normal stress stimulation, and the medial patellofemoral joint surface degenerates because of the lack of normal stress stimulation in patellar subluxation, resulting in nutritional impairment The medial patellofemoral joint surface degenerates due to lack of normal stress stimulation.
3, patellar mobility: in the fully extended knee position, place the two thumbs on the lateral edge of the patella and push the patella inward. Generally, a quarter of the width of the patella is defined as one degree. Under normal circumstances, the degree of internal displacement of the patella is between 1-2 degrees, more than two degrees indicates too much patellar mobility, less than one degree indicates tension in the lateral patellar support band, i.e. a positive test for limited internal displacement of the patella. For habitual patellar dislocation or subluxation, if the patellar internal displacement mobility is normal, the release of the lateral support band does not reduce the tendency of patellar dislocation, and bony surgery such as internal displacement of the tibial tuberosity should be the main focus.
4, medial synovial crease entrapment (Shelf’s disease): in the extended knee position, the patella is continuously pushed medially, and then the knee is gradually flexed, producing significant pain on the medial side of the patella when the knee is flexed close to 45°, and further flexion of the knee produces a popping sensation, and then the pain is relieved, which is positive for medial synovial crease entrapment. The medial synovial crease can be divided into three types: type I is the underdeveloped type, where there is only a remnant of synovial crease near the medial synovial wall; type II is the normally developed type, where the medial synovial crease is placed on the anterior medial joint capsule wall longitudinally from top to bottom like a shelf (Shelf), but there is no contact with the medial femoral condyle during knee extension and flexion activities; type III is the abnormal hyperplasia type, where the synovial crease is hyperplastic and thickened in the form of cords, which is in contact with the medial femoral condyle during knee extension and flexion activities. Type III is the abnormal hyperplasia type, which refers to the hyperplasia of the synovial crease in the form of cords that rub against the femoral condyle during knee extension and flexion. Synovial crease syndrome Type III synovial crease produces anterior medial knee pain symptoms. When the medial synovial crease is type III, pushing the patella inward in the extended knee position squeezes the crease between the patella and the medial femoral condyle, increasing the pressure between the patella and the medial femoral condyle with increasing knee flexion, thus increasing the pain symptoms, which are relieved when the synovial crease is released from the patellofemoral space and slides medial to the femoral condyle with further knee flexion. Medial synovial crease entrapment has a strong surgical indication for arthroscopic subsurface synovial crease resection.
5. Apprehenshion test: In the fully extended knee position, the patella is continuously pushed laterally and then the knee is gradually flexed. When the knee is flexed close to 45°, the patient develops a fear of patellar dislocation and refuses to proceed with the test, which is considered positive for phobia. The phobia test is one of the most sensitive tests to detect habitual patellar dislocation. Its significance is self-explanatory.
6, Quadriceps angle (Quadricep Angle → Q Angle → Q Angle): supine, extended knee position. From the anterior superior iliac spine to the patellar centroid and extend distally, and from the patellar centroid to the tibial tuberosity, the acute angle between these two lines is the quadriceps angle (Q angle). The normal quadriceps angle is 5°-10°. In general, for habitual patellar dislocation, if the quadriceps angle is greater than 15°, soft tissue surgery alone will not cure the dislocation, but should be combined with bone surgery.
Third, peripatellar pressure point – supine position
The periprosthetic pressure point is the most reliable basis for determining the specific cause of knee pain. Intra-articular and extra-articular factors can be initially identified based on the pressure points.
Lateral knee pressure points: at the head of the fibula – biceps femoris stopping point inflammation, caused by long-term tension activity of the biceps femoris, pain can radiate to the anterolateral part of the upper mid calf, combined with flexion resistance test can further confirm the diagnosis, N rope muscle stretching treatment is effective; lateral collateral ligament walking part – -The lateral collateral ligament injury; lateral femoral epicondyle – iliotibial tract infection, caused by contracture of the iliotibial tract or repeated irritation of the iliotibial tract at the site of the lateral femoral epicondyle, the diagnosis can be further confirmed by performing iliotibial tract distraction test, iliotibial tract distraction treatment is effective; lateral femoral epicondyle – N tendon stopping point infection, combined with flexion resistance test. -This can be caused by trauma, strain or irritation of the iliotibial bundle, and is referred to as lateral knee pain syndrome together with iliotibial bundle inflammation.
Anterolateral knee pressure points: superior patellar rim – quadriceps stop disease, caused by long-term high-intensity tension activity of the quadriceps muscle, positive resistance test for 90° knee extension; patellar tip and patellar ligament – patellar apophysitis and peripatellar tendonitis, positive resistance test for knee extension; tibial nodes – tibial nodal osteochondritis; medial patellar border – patellar subluxation or habitual patellar dislocation; medial patella – medial synovial crease syndrome; both sides of the patella to the tibia medial epicondyle – knee extension fasciitis, positive knee extension resistance test. Both sides of the patellar ligament – infrapatellar fat pad inflammation.
Medial knee pressure points: medial tibial tuberosity – goose foot stopping point inflammation, goose foot bursitis, caused by long-term N cord muscle tension activity, pain may radiate to the anteromedial calf, positive flexion resistance test; medial collateral ligament travel – medial collateral ligament injury. Posterior medial tibial plateau – hallux valgus stopping point inflammation.
Joint line plane – meniscal injury, joint capsule ligament injury, limited synovitis.
IV. Knee mobility – supine position
Restricted knee mobility is not a specific sign for the diagnosis of knee disease, but can be used as a test for disease progression and treatment outcomes. There are three specific forms of limited knee mobility: true interlocking, pseudo-interlocking, and end-of-motion limitation. True interlock refers to the inability to extend and flex the joint caused by the entrapment of material in the joint space. Broken cruciate ligament stumps, ruptured meniscus, intra-articular free bodies, abnormally enlarged synovium, and ruptured synovial folds can all cause true interlock. Pseudo-interlock refers to extension and flexion dysfunction caused by large intra-articular fluid accumulation, as the joint cavity is at its maximum capacity and least painful at 30° of knee flexion, so the affected knee always remains in the 30° of knee flexion position, similar to interlock. End of motion restriction means that the intermediate process of extension and flexion is normal, but cannot be completed until full extension or full flexion because of pain, and is commonly associated with chronic synovitis of the knee.
Knee mobility is recorded at 0° in neutral position. If a normal knee has 10° of hyperextension and 130° of flexion, 10°-0°-130° is recorded, and if a knee has 10° of limited extension and 90° of flexion, 0°-10°-90° is recorded.
V. Medial and lateral stability examination – supine position
Due to further understanding of knee stability structures, it is recognized that the lateral stability of the knee is not ensured by the medial and lateral collateral ligaments alone, but by the medial composite stability structure and the lateral composite stability structure of the knee. The medial composite structure includes the medial collateral ligament, the goose foot, the semimembranosus muscle, and the N oblique ligament, of which the goose foot, semimembranosus muscle, and N oblique ligament form the posterior medial angle, and the lateral composite structure includes the iliotibial bundle, the lateral collateral ligament, the biceps femoris tendon, and the N tendon, of which the lateral collateral ligament, biceps femoris tendon, and N tendon form the posterior lateral angle. Medial and lateral instability in the fully extended knee position: The affected foot is held in the axillary position, the calf is supported with both hands, and external and internal stresses are applied to check the laxity of the joint during external and internal rotation, respectively.
The degree of damage or laxity of the medial and lateral complex structures can be classified into three degrees. Theoretically, the degree of joint gap opening is differentiated by the degree of opening of 5 mm as first degree, 10 mm as second degree, and 15 mm as third degree. This is determined by stress radiographs and is often difficult to determine accurately during a clinical examination. Since the medial or lateral joint space is opened by approximately 1 mm for every 1° increase in valgus and valgus, the degree of medial or lateral joint space opening can be determined by the increase in valgus and valgus angles during the physical examination. Medial instability of the knee is considered to be first degree when the valgus angle increases to 5°, second degree when it increases to 10°, and so on.
In the fully extended knee position, medial knee stability is ensured first by the tight posterior medial angle, followed by the lateral collateral ligaments, and then by the cruciate ligaments. When there is significant valgus instability in the fully extended knee position, it often means that all three groups of structures are damaged at the same time. When only the medial collateral ligament or the cruciate ligament is injured, it does not show changes in valgus stability because of the integrity of the posterior medial angle. Similarly, in the fully extended knee position, the lateral stabilizing structures of the knee are ensured first by the tight posterior lateral horn, followed by the iliotibial and capsular ligaments, and then by the cruciate ligaments. When there is significant medial instability in the fully extended knee position, it also means that all three groups of structures are damaged at the same time.
Medial and lateral instability at 20° of knee flexion: Holding the affected foot in the same position as above, with both hands on the lower leg, the knee is flexed at 20° and the degree of stability of the medial and lateral knees is examined by applying external and internal stresses respectively. The degree of instability was graded as in the fully extended knee position. When the knee is flexed at 20°, the posterior medial and posterior lateral angles are relaxed, and the stability of the medial knee is provided first by the medial collateral ligament, followed by the cruciate ligament; the stability of the lateral knee is provided first by the iliotibial bundle, lateral collateral ligament and joint capsule ligament, followed by the cruciate ligament. Therefore, when medial instability of the knee occurs, it is first indicated by injury to the medial collateral ligament, which can be accompanied by injury to the cruciate ligament as the instability increases. When lateral instability of the knee occurs, it first indicates injury to the iliotibial bundle, lateral collateral ligaments, and capsular ligaments, which can also be associated with increased instability.
In combination with the medial and lateral stability examinations of the knee in the fully extended and 20° flexed knee positions, it is possible to broadly identify those knee stability structures that are damaged. For example, if the knee is unstable medially at 20° flexion and stable in full extension, this indicates a simple medial collateral ligament injury; if the knee is unstable medially at 20° flexion and in full extension, this indicates an injury to the entire medial complex; if the knee is unstable laterally at 20° flexion and stable in full extension, this indicates an injury to the iliotibial bundle, lateral collateral ligament, and lateral capsular ligament; if the knee is unstable laterally at 20° flexion and in full extension, this indicates an injury to the entire lateral complex. When the knee is unstable in both the 20° flexion and full extension positions, it indicates damage to the entire lateral complex. Severe medial and lateral instability of the knee may include cruciate ligament injury.
VI. Axial shift test and reverse axial shift test – supine position
Axial shift test: Fully straighten the knee joint, hold the affected foot in the axilla as in the examination of the medial stability of the knee joint, hold the calf with both hands and apply external rotation stress, gradually flex the knee joint, when the knee is flexed close to 20°, the popping sound of the lateral tibial plateau moving forward can be felt, continue to flex the knee joint, when it is close to 40°, the popping sound of the lateral tibial plateau resetting can be felt, this is a positive axial shift test.
Reverse axis shift test: one hand holds the foot, the other hand holds the calf, first flex the knee to the maximum, while externally rotating the calf, if there is posterior lateral angle instability, then there will be a dislocation of the lateral tibial plateau to the posterior lateral side, then apply external rotation stress, and gradually extend the knee joint, at close to 40°, due to the iliotibial bundle from the posterior side of the lateral femoral epicondyle sliding to the anterior side, drive the lateral tibial plateau reset and produce a popping sensation, this is This is a positive reverse axial shift test.
In other words, the axis of the tibia itself is moving around another abnormal axis, hence the name “axial shift”. The axial shift test and the reverse axial shift test do not correspond to the ligamentous structures examined. The axial shift test examines the damage or laxity of the anterior cruciate ligament, while the reverse axial shift test examines the integrity of the posterior lateral horn.
When the knee is flexed close to 20°, the posterior lateral angle is relaxed and the pulling force on the lateral tibial plateau is weakened to the posterior lateral side, and if there is a rupture or laxity of the anterior cruciate ligament at the same time, the lateral tibial plateau will be displaced to the anterior lateral side due to the forward pulling of the iliotibial bundle. When the knee is flexed close to 40°, the iliotibial bundle slides from the anterior to the posterior aspect of the lateral femoral epicondyle, pulling the lateral tibial plateau back to the lateral side, and the same popping sensation occurs when external rotation stress is applied. A positive axial shift test can be divided into four degrees: first degree refers to a positive axial shift test when internal rotation stress is applied to the lower leg and a negative axial shift test when the lower leg is rotated in neutral; second degree refers to a positive axial shift test when the lower leg is rotated in neutral and a negative axial shift test when external rotation stress is applied; third degree refers to a positive axial shift test when external rotation stress is applied to the lower leg; and fourth degree refers to a positive axial shift test with significant lateral composite structural instability. A first-degree positive test indicates only ACL laxity, while a second-degree positive test or higher indicates ACL rupture. The reverse axial shift test is not used to diagnose posterior cruciate ligament injury; a positive result indicates posterior lateral horn injury.