6.1 Introduction
The knee joint is not only the largest joint of the body; it is also the joint with the most complicated biomechanics. It connects the longest bones to each other, has the largest articular cavity, has the largest sesamoid bone (the patella), and has the largest capsule (Matthijs et al., 2006). Therapists frequently have to deal with this joint in their daily work. Post-traumatic and postoperative treatment of the joint is part of the work of almost every rehabilitation clinic or physical therapy practice.
Comparatively, the large number of knee operations is extraordinary. The common indications for surgical intervention are arthritic changes in articular surfaces and injury to the complex ligamentous construction and the menisci. In the USA, more than 966,000 total knee arthroplasties were carried out in 2017 (HCPUnet, iData Research, 2018). According to estimates by Maradit Kremers et al. (2015) around 7 million Americans are living with a hip or knee replacement. In Germany, approximately 108,000 knee replacements were implanted in women alone in 2015. This makes this knee procedure the eleventh most common surgical procedure in women in Germany (German Federal Statistical Office, 2017). In addition to appropriate postoperative treatment, which has become quite sophisticated, the therapist also encounters traumatic and nontraumatic joint symptoms that at first seem difficult to classify and that require a systematic and technically precise examination procedure. Target-oriented palpation, combined with systematic interrogation and diagnosis, play a central role in identifying the location and cause of the symptoms.
6.2 Significance and Function of the Knee Joint
One of the basic principles of joint function in the lower limbs will also become obvious in the knee joint. It must be possible to lock the lower extremity into a stable weight-bearing pillar that also has remarkable mobility.
This knee joint mobility calls for a great deal of flexion that decreases the distance between the foot and the body. In such ordinary situations as squatting, climbing stairs with high risers, or getting into a car, it becomes clear why a high degree of flexion is necessary.
The second form of mobility is the rotation of the knee joint. This movement is linked to the angle of knee joint flexion and is only possible between approximately 20 and 130°. Between 20° flexion and maximal extension the knee joint is locked in terminal rotation. When the leg is loaded and in end-range extension, the femur rotates inward and the tibia, in open chain, turns in end-range outward rotation. If active rotation in end-range extension were possible, it would presumably be at the cost of stability, which is of particular importance in the extended position.
The ability of the foot to rotate is mainly anchored in the knee joint. The remaining rotation takes place in the motor complex consisting of the talotarsal joint and the transverse tarsal joints.
This capacity for rotation of the tibia in the knee joint places specific demands on the construction of the articulating bones at the knee joint. Axial rotation of the leg at the knee joint requires a central rotary column (primarily the posterior cruciate ligament), a flat rotary plate (proximal end of the tibia), and articular surfaces with almost only one single point of contact.
This flat rotary plate causes a high degree of incongruence between the articular surfaces. The knee would be unable to rotate as well if the tibial articular surface were more curved. Although incongruence facilitates rotation, stability and the transfer of load suffer. The menisci complement this joint, forming a mobile articular socket to balance the pointlike contact between the articular surfaces and to lubricate the joint.
As stability can no longer be provided by the bones, internal and external ligamentous structures (cruciate and collateral ligaments) as well as sections of muscle that radiate into the capsule (dynamization) fulfill this function. All these ligaments give each other functional support (Matthijs et al., 2006).
The cruciate ligaments are responsible for the primary security of the joint in the sagittal plane. This function can also be assessed using a test conducted in the sagittal plane, the drawer test, and the Lachman test. These ligaments also modulate tension to control the arthrokinematics during flexion and restrict the amount of medial rotation.
Knee joint stabilization in the frontal plane is the function of both the collateral ligaments and the posterior capsule.
The dynamization of different collagenous structures at a joint is not peculiar to the knee joint. However, it is quite distinct in this region. Dynamization in this context means that muscles, and sometimes their tendons, are attached to the capsule or menisci. Different sections of the capsule are placed under tension and strengthened when these muscles contract. During active movement of the knee, the femoral condyles not only roll over the menisci on the tibia in an anterior or posterior direction, the contraction of muscles also pulls on the menisci and causes movement.
6.3 Pathological Conditions and Common Applications for Treatment
6.3.1 A Selection of Possible Pathologies
It is beyond the scope and objectives of this book to list all types of disease and injuries seen in the knee joint. Therefore, only the most important groups are listed below:
Capsular and noncapsular restrictions in movement.
Traumatic and degenerative meniscus pathology, impingement of the meniscal horns.
Injuries to ligaments or ligamental overuse syndromes.
Injuries to the muscles or muscular overuse syndromes (including tendons and insertions).
Disease of the femorotibial articular cartilage (for instance, osteoarthritis or osteochondrosis dissecans).
Patellofemoral pathologies (for instance, chondromalacia patellae or patellofemoral pain syndrome, “young girl’s knee syndrome”).
6.3.2 Common Assessment and Treatment Techniques
Assessment and mobilization of existing restrictions in mobility.
Improvement of muscular tracking of the joint in cases of instability.
Treatment of injuries in ligaments and muscles or the symptoms associated with overloading.
The high prevalence of irritation or injury to ligaments, tendons, and bursae shows in the established use of independent terms such as runner’s knee (iliotibial band friction syndrome), jumper’s knee (insertion tendinopathy of the patellar ligament at the apex of the patella), and housemaid’s knee (prepatellar bursitis).
6.4 Required Basic Anatomical and Biomechanical Knowledge
Therapists must have a good basic knowledge of anatomy to locate specific important structures in the knee joint and its surroundings. Therapists are familiar with most bony and ligamentous structures through their training/studies and professional experience. It is important to develop a good spatial sense so that the construction of the joint can be considered from different perspectives. Presenting the structural complexity of the knee joint is beyond the scope of this book. Therefore, in what follows, only basic concepts will be discussed.
The knee joint is subdivided into the femorotibial joint and the patellofemoral joint.
6.4.1 Construction of the Femorotibial Joint
Embryologically, the knee joint develops from two structures, the medial and lateral compartments. The original synovial dividing wall gradually disappears in the course of development and only remains as the synovial plica. This original division can, however, be retained for anatomical and functional reasons. It is always true that the lateral compartment is more mobile. The slightly convex shape of the lateral tibial condyle and the more mobile, lateral meniscus, O-shaped and more deformable, back this up. In the frontal view, the knee joint can be divided into three levels (Matthijs et al., 2006):
Femorotibial joint: selective, direct contact between femoral condyles and tibial condyles.
Meniscofemoral joint: contact between the femoral condyles and the menisci.
Meniscotibial joint: contact between the tibial condyles and the menisci.
The associated capsular portions are described in the same way, for example, meniscofemoral capsular portions.
The femur widens at the distal end and has two condyles (▶ Fig. 6.1). This may lead to classifying the knee joint as a condylar joint. Nevertheless, with its movements in flexion, extension, and inward and outward rotation, it must be classified as a trochoginglymus joint. The medial femoral condyle is longer than the lateral, to compensate for the oblique position of the femur. In contrast, the lateral condyle stands out somewhat further to anterior and acts as a lateral resistance to the patella.
The femoral condyles, together, form a grooved patellar face as a component of the patellofemoral joint. Distally and posteriorly, the condyles diverge and form the intercondylar fossa, which is approximately 20 to 22 mm wide (Wirth et al., 2005), the resting place of the cruciate ligaments. Both femoral condyles are convex. In the sagittal plane, their curvature increases posteriorly (▶ Fig. 6.2), more distinctly in the lateral condyle. Accordingly, the articular surfaces of the condyles with the tibial condyles are smaller in flexion than in extension. The femoral condyles have an impression line, the sulcus terminalis, which in end-range extension points to the tibia and the anterior horns of the meniscus. In loaded position, pressure on the meniscus and tibia laterally initiates terminal rotation—with the medial condyle sliding to posterior with a longer gliding movement—and thus forces the femur to rotate inward. Proximal to the articular body, the femur has a medial and a lateral epicondyle, attachment points of the collateral ligaments.
The club-shaped enlargement of the proximal tibia (see ▶ Fig. 6.1 ) forms two cartilage-covered facets (tibial condyles) and an intercondylar area with the intercondylar eminence. These are the points of attachment for both menisci and both cruciate ligaments. Seen frontally, both tibial joint surfaces are slightly concave. Sagitally, the medial joint surface remains concave. In contrast, the lateral joint surface is slightly convex, which facilitates the arthrokinetic roll components in the lateral compartment. Further, seen in the sagittal plane, the tibial plateau falls off from the level of the tibial longitudinal axis by approximately 10° (Matthijs et al., 2006). In the embryo, this angle is 45° and regresses to varying degrees intraindividually. For this reason, it is very variable. On the proximal tibia, there are two large rough areas for the insertion of strong ligaments: the tibial tuberosity for the patellar ligament and the Gerdy tubercle for the principal insertion of the iliotibial tract. The two rough areas and the head of the fibula form an equilateral triangle.
Occasionally an additional sesamoid bone can be found in the knee joint. The fabella is embedded in the tendon of the lateral head of the gastrocnemius muscle at the level of the lateral femoral condyle. Reported figures for the frequency of occurrence of a fabella as a bone vary from 8 to 20% (Petersen and Zantop, 2009). If the fabella is not present as a bone, it can occur as a fibrous or fibrocartilaginous structure. It is in contact with important ligaments of the posterior capsule (oblique popliteal, arcuate popliteal, and fabellofibular ligaments).
The menisci, movable cups, equilibrate the incongruence between the femoral condyles and the tibia, bear weight when the joint is under load, and press synovia against the articular cartilage of the articulating condyles during movement, thus building a foundation for cartilage nutrition.
As central pillars or intracapsular ligaments, the cruciate ligaments control the arthrokinematics of the knee joint, ensure the integrity of the joint in the sagittal plane, and limit inward rotation. They usually run from the femoral intercondylar fossa to the tibial intercondylar area. They consist of several bundles of high tensile strength, helical type I collagen, encased in a synovial membrane. Strictly speaking, they are thus situated within the fibrous capsule (intra-articular) but without direct contact with the synovia (extrasynovial). Some parts of the cruciate ligaments are isometric and remain tensed in every joint position (companion bundles). Other portions are increasingly recruited in end-range movements (safety bundles; Fuss, 1989).
The capsule can be subdivided in various ways. Superficial and deep portions can be distinguished, or distinctions can be made according to direction. Thus, a distinction is made among the following:
Medial capsule portions with the reinforcing medial collateral ligament (except at the level of the joint capsule).
Lateral portions without direct reinforcement by the lateral collateral ligament.
An anterior capsule with the patellar ligament, longitudinal and transverse retinacula, and the patellomeniscal ligaments. The anterior capsule forms a suprapatellar recess that inserts at the posterior half of the patellar base and displaces the patella downward by up to 8 cm under increasing flexion.
Strengthening of the posterior capsule, for instance laterally, by the arcuate popliteal ligament and medially by the oblique popliteal ligament.
Protection in the frontal plane is provided by the collateral ligaments and the posterior capsule. The tension of all components increases with extension. The posterior capsule primarily protects in complete extension, whereas the collateral ligaments provide the primary stability against varus and valgus stress beginning with slight flexion. The two collaterals differ morphologically and work synergistically in limiting outward rotation.
The medial collateral ligament has its femoral origin at the medial femoral epicondyle and the adductor tubercle and becomes significantly wider (3–4 cm) at the level of the articular space. According to Liu et al. (2010), it runs for a further approximately 6.2 cm from the articular space to the medial surface of the tibia, below the superficial pes anserinus. It has a superficial (anterior) and a deep (posterior) portion. The superficial portion twists during knee flexion and is therefore palpable as a convexity over the articular space. The posterior portion is in close contact with the base of the medial meniscus.
The lateral collateral ligament is comparatively short (approximately 5 cm), rounded, and thin. It has no capsular or meniscal contact. Its points of fixation are the lateral femoral epicondyle and the head of the fibula.
6.4.2 Construction of the Patellofemoral Joint
When seen from the front, the patella, the largest sesamoid bone in the human body, is basically triangular (▶ Fig. 6.3). The rounded base of the patella is about 1.5 cm thick and functions posteriorly as the point of insertion of the suprapatellar bursa and anteriorly as the point of insertion of the largest part of the quadriceps femoris. At 90° the base of the patella is flat and parallel to the shaft of the femur. For this reason, the anterior edge of the base is very simple and the posterior edge very difficult to palpate. The base is bounded laterally by projecting corners: the medial and lateral poles of the patella. From this point, the patella narrows to its apex, which is generally located at the level of the femorotibial articular space. The distal third is the point of insertion of the patellar ligament, both at the edges and to a lesser extent at the anterior and posterior surfaces. At the middle of the posterior surface of the patella is a longitudinal ridge, from which medial and lateral facets extend. These together make up the articular surface of the patella. The longitudinal eminence articulates with the groove of the femoral patellar surface, which, in extension, is the articulating partner. With increasing flexion, the lateral surfaces of the patella glide over the femoral condyles. During an extensive flexion, the patella describes movements that can be classified as:
6.4.3 Proximal Tibiofibular Joint
In contrast to the elbow joint, only one bone in the medial joint of the lower extremity, the tibia, articulates with the bone of the proximal section of the extremity, the femur. The fibula forms an amphiarthrosis with the posterolateral head of the tibia; its articular space is oriented at approximately 45° from anterolateral to posteromedial (see ▶ Fig. 6.2). In some cases, the joint cavity communicates with the cavity of the femorotibial joint and must then be considered as a part of the knee joint. Functionally, the proximal tibiofibular joint (TFJ) is part of the tibiotarsal motor complex and moves in accompaniment with foot extension and flexion and all associated movements, especially in an anteroposterior direction. It is protected by ligaments that provide force closure and acts as point of insertion for several muscles, the most important being the biceps femoris. The biceps has a basically dislocating effect on the proximal TFJ.
6.4.4 Muscles of the Knee Joint
The quadriceps femoris muscle is the most important in extension of the knee joint (▶ Fig. 6.4). Its fibers insert in part at the anterior base of the patella and also run anterior via the patella and parapatellar as longitudinal retinacula, to the tibia. The vastus medialis, arising in part from the tendon of the adductor magnus (Scharf et al., 1985) offers active resistance to the tendency for lateral movement, since it inserts at the chief medial stabilizer of the patella, the medial patellofemoral ligament (Panagiotopoulos et al., 2006). Probably the largest individual muscle in the body, the vastus lateralis inserts with a 5-cm-long tendon at the lateral aspect of the patellar base. The thickening of the muscle belly in contraction spans the iliotibial tract from the interior outward. Below the rectus femoris, as a branch of the vastus intermedius, is the articularis genus muscle. Its fibers radiate in the popliteal recess and, in active knee extension, span the recess and prevent femoropatellar impingement.
The flexors of the knee joint are more distinctly differentiated; they are the group of inward and outward rotators (▶ Fig. 6.5). The ischiocrural muscles (hamstrings) can be considered as agonists, while the further portions of the pes anserinus (sartorius and gracilis muscles) as well as the heads of the gastrocnemius and popliteal muscles act synergistically. The distribution of the ischiocrural muscles on the distal thigh forms the proximal half of the rhomboid popliteal fossa.
The principal outward rotator, the biceps femoris, has a very variable distribution of its insertion tendon. It inserts chiefly at the head of the fibula (▶ Fig. 6.6), at the crural fascia and the tibia (Tubbs et al., 2006). Its fibers embrace the lateral collateral ligament. Some fibers radiate into the arcuate ligament of the knee and the tendon of the popliteal muscle (ibid.). Radiation into the posterior horn of the lateral meniscus is also described.
Another important structure is found lateral to the iliotibial tract. The tract, dynamized by the tensor fasciae latae, gluteus maximus, and vastus lateralis, functions as reinforcement of the lateral thigh fascia, which is located close to the lateral intermuscular septum. Directly proximal, it receives ligamentary radiations from the femur (Kaplan fibers). Its distal insertion is chiefly on the Gerdy tubercle, anterolateral on the tibial head. Other radiations are the fasciae of the foot extensors and the proximal and anterior patella (iliopatellar ligament), which can also create a tendency to move the patella to one side. At approximately 30 to 40° flexion of the knee joint, the tract is located directly over the lateral epicondyle. With increasing extension, it has an extensor effect; with increasing flexion, it acts as a flexor synergist. In addition, it has an external rotatory effect on the knee joint.
Medially, the pes anserinus muscles are the dominant anatomical feature (▶ Fig. 6.7). It is well known that fibers of the sartorius, gracilis, and semitendinosus muscles end in the superficial pes anserinus. These can be well differentiated proximal to the joint. Distal to the articular space, they run together in a broad insertion tendon that inserts at the medial tibial surface. They cross the knee joint behind the flexion/extension axis and thus act as flexors and inward rotators. A series of small bursae protects the insertion plate against friction from the medial collateral ligament and the tibial periosteum. The deep pes anserinus is formed by the tendon of the semitendinosus muscle that divides into five insertion bands. In addition to two insertions at the tibia, there are the radiations into the fascia of the popliteal muscle, the posterior horn of the medial meniscus, and the posteromedial capsule (oblique popliteal ligament). Its tendon is clearly prominent in the posterior thigh during flexion.
To posterior, the gastrocnemius is dominant at the surface; it forms the distal half of the rhomboid popliteal fossa with the division of its two bellies. Deep portions of the tendon radiate into the posterior capsule. The popliteal muscle is fleshy at its origin on the posterior proximal tibia. Its muscle belly is anterior to the medial gastrocnemius head and is therefore not directly palpable. The tendon that runs upward to proximal and lateral divides into three portions that insert at the medial meniscus and radiate into the posterolateral capsule. The actual insertion tendon crosses the articular space between the lateral collateral ligament and the joint components femorotibially and inserts approximately 0.5 cm distal and anterior to the lateral epicondyle.
From the introduction to the muscles of the knee joint presented so far it becomes clear that in addition to motor functions, the radiations into capsules, fasciae, or menisci are an important anatomical fact. The effect is the tensing of these structures with muscle contraction, which is called dynamization. At other joints, such as the shoulder joint, dynamization is also known. However, the difference in contact of muscles to articular structures is particularly pronounced here, at the knee joint. ▶ Table 6.1 provides a summary of all dynamizations.
6.4.5 Neural Structures
The most important neural structures pass along the back of the knee. Only a large branch of the femoral nerve, the saphenous nerve, crosses the joint medially (see ▶ Fig. 6.7). Its position is very variable. Usually it comes to the surface between the sartorius and gracilis muscles and runs subcutaneously in a distal direction (von Lanz and Wachsmuth, 2003).
Approximately 1 hand width proximal and posterior to the knee joint, the sciatic nerve separates into its two divisions. The tibial nerve runs through the middle of the popliteal fossa. Its expected size lies between the diameter of a pencil and that of a little finger. After branching from the tibial nerve, the peroneal nerve runs laterally and accompanies the biceps tendon to the head of the fibula. Distal to the fibular head, it crosses to anterolateral and branches again. At the level of the biceps tendon, the nerve is shifted approximately 1 cm to medial.
6.5 Palpation for Warmth and Swelling
6.5.1 Palpating an Increase in Temperature
An increase in temperature may be a sign of capsule irritation. The therapist can decide if this is the case by comparing sides and by also comparing the knee with the proximal and distal soft tissues. Obviously, both knees should have the same temperature when normal (▶ Fig. 6.8). However, examination of the joint in relation to its surroundings is of interest. The therapist can assume that a nonpathological joint feels colder than its surroundings, that is, compared with the soft tissues proximally and distally/laterally.
6.5.2 Palpating Edema
Summary of the Palpation Process
Swelling appears in various joint diseases and injuries involving, for instance, capsular ligaments, menisci, and cruciate ligaments. If it occurs within one hour after a trauma, the swelling is very probably a hemarthrosis. Slowly emerging articular effusions are most likely synovial in nature. Nontraumatic swelling that occurs immediately after stress is a sign of a cartilaginous lesion. On the other hand, gradually developing swelling after stress more probably indicates degenerative meniscopathy. In any case, swelling is a sign of joint disease. A detailed diagnosis, if necessary with additional joint-challenging tests designed to test stability and provoke pain, can in itself cause or intensify effusion and increased warmth around the joint.
Techniques will be described that identify the presence of edema in the joint in terms of:
Starting Position
The patient is either lying prone or sitting with their legs stretched out on a treatment table. The affected knee joint is extended as far as possible without aggravating pain. However, the knee must be fully extended to identify a small effusion, otherwise the test will most likely result in a false negative.
Large Effusions
It is not difficult to recognize a large joint swelling by visual inspection and palpation. In extension, the capsule is tight, posteriorly and laterally. In an intra-articular effusion, the fluid collects anteriorly, under the patella, and sometimes raises it.
Technique
This test aims to collect the synovial fluid underneath the patella and to identify the extent of the edema by applying pressure to the patella.
The thumbs of both hands are abducted here. The distal hand is positioned over the joint space of the knee. It prevents the synovial fluid from spreading distal and lateral to the patella (▶ Fig. 6.9).
The proximal hand starts stroking widely over the thigh approximately 10 cm superior to the patella so that the synovial fluid is milked out of the suprapatellar pouch and accumulates underneath the patella. This raises the patella. One finger of the proximal hand is then placed on the patella. Pressure is exerted in a posterior direction until the patella is once more in contact with its femoral glide.
The criterion for comparing swelling on the two sides is the time required for the patella to come in contact with the femur. The intra-articular effusion is then pressed against the palpating finger in a medial and lateral direction. The sign of a dancing patella is not present if extra-articular swelling is present (Strobel and Stedtfeld, 2013).
This test is also called the “dancing patella” test, “ballotable patella” test, or “patella ballottement” test, or the “patella tap” test. Execution of the test varies significantly. All forms are permissible providing the following details are observed: the fluid is gathered under the patella and held there while direct pressure to posterior is exerted on the patella.
Medium-sized Effusions
The “dancing patella test” is quite common; the test to identify medium-sized effusions is used less often.
Technique
The proximal hand again strokes distally. The distal hand forms a tight V between thumb and index finger. This V is supported from distal against the lateral borders of the patella and the finger pads are placed on the articular space (▶ Fig. 6.10).
During stroking, the synovial fluid is pushed distally underneath the patella. The V-formed hand feels an increase in pressure as the synovial fluid spreads out.
The criterion for this test is the possibly different magnitude of this pressure on the two sides.
Minimal Effusions
It is very simple to identify a moderate- or large-sized edema in the knee joint. Recognition of a minimal effusion requires a special technique. The starting position must be full extension, held passively.
Technique—Phase 1
The therapist broadly strokes the medial side of the knee joint to proximal-lateral, at least three times (▶ Fig. 6.11). In this way, the synovial fluid is shifted to other parts of the joint.
Technique—Phase 2
Immediately thereafter, the lateral aspect of the knee joint is widely stroked once in a proximal direction, which pushes the synovial fluid into the joint cavity and to medial (▶ Fig. 6.12). The therapist simultaneously observes the medial joint space adjacent to the patella, which usually takes on a slightly concave shape. In a normal joint, there is a slight concavity here that remains concave if the effusion test is negative. When a small joint effusion is present, a small “bulge” is produced in the medial concavity while stroking the lateral side of the knee.
6.6 Local Palpation—Anterior
6.6.1 Summary of the Palpatory Process
Anterior palpation locates the boundaries of the patella and their connection to the tibia (▶ Fig. 6.13).
Starting Position
The patient sits in an elevated position, for example, on the edge of a treatment table. The therapist either sits in front of the patient or a little to the side (▶ Fig. 6.14).
When possible, the leg should hang freely over the couch and be able to flex freely when the therapist’s hand facilitates movement.
This starting position (SP) ensures that the palpable structures on the anterior, medial, and lateral sides of the knee joint are freely accessible. This SP should only be considerably altered when palpating the posterior aspect of the knee. The patient exerts no static effort to retain this starting position and all muscles are relaxed. The patellar ligament is moderately tensed, and the entire base of the patella is accessible.
Alternative Starting Positions
The SPs described above are mainly used when practicing. Other SPs may be necessary in the everyday assessment and treatment of the knee joint. In these cases, the therapist may have to approach the knee from a different angle and position the knee with a different amount of flexion.
When the following palpation has been correctly applied to study partners or patients, it should be repeated in its modified forms:
When the knee is fully extended it is easier to palpate the base and the poles and more difficult to palpate the apex of the patella and the ligament through the laterally protruding infrapatellar Hoffa fat pad.
With increasing flexion due to increasing contraction of the anterior structures, all contours will be more difficult to find. Arthritis-related edema and bony deformation alter the expected consistency and contours of the respective structure.
6.6.2 Palpation of Individual Structures
Base of the Patella
The search for the borders of the patella begins at its base. As already mentioned in the topographic introduction to the knee joint, the base of the patella is very thick and has a front and back boundary.
When the knee is extended, only the anterior edge of the patellar base can be easily reached. It connects both poles in a curved line. Pressure on the apex can be used to tip the base upward and make the posterior edge accessible.
The posterior edge is the most important border in the flexed position. The palpation aims to identify this edge and differentiate it from the femur and the surrounding soft tissues. When the knee joint is flexed, the patellar base is parallel to the thigh and follows the shape of the patellar surface of the femur. Therefore, its boundaries can only be palpated during slight passive extension/flexion movement of the knee joint (▶ Fig. 6.14).
The facilitated movement of the lower leg should be minimal and completely passive! Any activity of the quadriceps makes locating the base of the patella extremely difficult.
Technique
The therapist places several fingertips on the thigh approximately 3 to 4 cm proximal to a line connecting the medial and lateral poles of the patella. They point to distal for transverse palpation of the edges (see ▶ Fig. 6.13). The second hand moves the joint in small, passive motions. This causes the patella to also describe small motions to proximal and to push its posterior edge against the fingertips of the palpating hand, and thus be located. The posterior edge can be followed to medial and lateral to both poles. This line tapers off somewhat in the center and thus represents the extension of the posterior groin, which separates the medial from the lateral facet. The anterior surface is not as wide as the posterior surface, so that an incline to the palpated edge drops off from the anterior surface to each side. To record the length of this anterior surface, a line can be drawn outlining it, starting from where the incline begins. Ultimately, two outlines of the patella are created.
Edges of the Patella
The borders of the patella are now defined by following the contours with transverse palpation, past both poles to the apex (▶ Fig. 6.15).
Technique
Compared with the medial side, it is relatively difficult to identify the exact border of the lateral pole of the patella. The lateral femoral condyle projects further to anterior than the medial condyle; its outline is similar to the shape of the patella. The knee joint must be moved occasionally to differentiate the patella from the lateral femoral condyle. The previously described perpendicular technique is used for palpation.
Apex of the Patella
The patellar ligament uses the distal third of the patella, including the apex, as proximal area of attachment. This distal border of the patella can therefore only be reached via the ligament.
Technique
The palpating hand approaches the apex using a perpendicular technique once more. Firm pressure is initially applied to the patellar ligament, which responds with a pronounced firm consistency. While maintaining the pressure on the ligament, the palpating fingertips attempt to make contact with the more proximal apex. The consistency of the apex is expected to be hard and the edge distinct (▶ Fig. 6.16). The edges of the patella in the area of the ligament’s insertion can easily be located with the same technique.
Several soft-tissue pathologies of the patellar ligament (tendinosis, jumper’s knee) can be located here. Therefore, precise pinpointing techniques are of great advantage. The treatment of these conditions will be discussed later in the text.
Patellar Ligament, Differentiation
The patellar ligament must be differentiated from the bony fixed points at its origin (patellar apex) and insertion (tibial tuberosity). Furthermore, the lateral contours can be discerned. Two techniques for this purpose will be described below:
▶ Method 1. Starting at the apex, the therapist palpates slightly more distally so that the fingers are directly on top of the ligament. The side borders are then sought from this position.
▶ Method 2. Two shallow indentations are found at the level of the patellar apex in knee joints, which are neither swollen nor arthritic. The anterior knee joint space can be accessed here. Starting at these indentations, the therapist palpates anteriorly and encounters the firm yet somewhat elastic consistency of the patellar ligament.
The edges of the ligament can be followed from the patella onto the tibial tuberosity (▶ Fig. 6.17). The palpation reveals that:
Tibial Tuberosity
The tuberosity tapers off distally and merges into the anterior border of the tibia. This border can be easily palpated along the entire length of the leg. On its medial aspect, the tibia possesses a surface with a boundary posterior to the medial border of the tibia. A rough area is found on the lateral and proximal aspects of the tuberosity at the insertion of the iliotibial tract (Gerdy tubercle).
Technique
The patellar ligament is differentiated from the tibial tuberosity using the same technique (perception of differences in consistency) as for the apex.
With direct pressure on the ligament, a firm but elastic consistency is felt (▶ Fig. 6.18). If palpation is continued in a distal direction, the tuberosity is located as a distinctly hard resistance. The transition from elastic to hard consistency marks the proximal boundary of the tuberosity. Its greater size can be perceived by circular palpation with a flat fingertip. This is particularly successful in the case of a shape distorted by aseptic osteonecrosis (Osgood-Schlatter disease).
Insertion tendinopathies at the distal insertion of the ligament are well known but relatively rare. Now and then this region is painful to pressure because of bursitis, where the movement of fluid in the inflamed deep infrapatellar bursa (under the inserting ligament) or subcutaneous bursa of the tibial tuberosity (directly on the tuberosity) can be felt.
6.6.3 Tips for Assessment and Treatment
The palpation techniques used for the anterior region of the knee are used in two common assessment and treatment techniques:
The assessment of mobility of the patellofemoral joint.
Transverse frictions at the patellar ligament and the apex of the patella.
Techniques at the Patellofemoral Joint
Examining or restoring mobility of the patella on its femoral glide is important in postoperative treatment, for maintenance or restoration of knee flexion.
In the very early phases of postoperative treatment, this is possible when the knee is almost fully extended. It is easiest to move the patella in all directions in this position as the surrounding structures are most relaxed.
Treatment aims to preserve the elasticity of the capsule and the suprapatellar pouch in particular. Therefore, it is most important to maintain patellar mobility in a distal direction.
If necessary, stretching is used to restore mobility at a later stage of postoperative treatment. This only makes sense when the knee is positioned at maximum flexion. The knee is therefore assessed starting in this position and, when necessary, mobilized.
Surface anatomy techniques help therapists to locate the base of the patella precisely and to apply treatment effectively, even in joints that are still swollen. In this process, either the fingertips of the distal hand or the base of the proximal hand is placed on the base of the patella to exert a push to distal (▶ Fig. 6.19).
