Dr. anurag applied anatomy of knee

PMR PG Teaching

1. Applied Anatomy Of Knee -Dr Anurag Ranga

2. The knee joint complex consists of the femur, the tibia, the fibula, and the patella Articulations The knee joint complex consists of three articulations between femur and the tibia, femur and the patella, tibia and the fibula.

3. Characterized by two large condyles, which articulate with the proximal head of the tibia. The condyles are separated posteriorly by an intercondylar fossa and are joined anteriorly where they articulate with the patella. The surfaces of the condyles that articulate with the tibia are rounded posteriorly and become flatter inferiorly. The walls of the intercondylar fossa bear two facets for the superior attachment of the cruciate ligaments, which stabilize the knee joint. The wall formed by the lateral surface of the medial condyle has a large oval facet, which covers most of the inferior half of the wall, for attachment of the proximal end of the posterior cruciate ligament ; The distal end of femur

4. The wall formed by the medial surface of the lateral condyle has a posterosuperior smaller oval facet for attachment of the proximal end of the anterior cruciate ligament Epicondyles, for the attachment of collateral ligaments of the knee joint, are bony elevations on the nonarticular outer surfaces of the condyles. Two facets separated by a groove are just posterior to the lateral epicondyle : the upper facet is for attachment of the lateral head of the gastrocnemius muscle; the inferior facet is for attachment of the popliteus muscle. The medial epicondyle is a rounded eminence on the medial surface of the medial condyle. Just posterosuperior to the medial epicondyle is the adductor tubercle.

5. PR0XIMAL END OF TIBIA The proximal end of the tibia is expanded in the transverse plane for weight bearing and consists of a medial condyle and a lateral condyle , which are both flattened in the horizontal plane and overhang the shaft. The superior surfaces of the medial and lateral condyles are articular and separated by an intercondylar region, which contains sites of attachment for strong ligaments (cruciate ligaments) and interarticular cartilages (menisci) of the knee joint.

6. The articular surfaces of the medial and lateral condyles and the intercondylar region together form a "tibial plateau," which articulates with and is anchored to the distal end of the femur. Inferior to the condyles on the proximal part of the shaft is a large tibial tuberosity and roughenings for muscle and ligament attachments. The medial condyle is larger than the lateral condyle and is better supported over the shaft of the tibia. Its superior surface is oval for articulation with the medial condyle of the femur. The articular surface extends laterally onto the side of the raised medial intercondylar tubercle The superior surface of the lateral condyle is circular and articulates above with the lateral condyle of the femur.

7. The medial edge of this surface extends onto the side of the lateral intercondylar tubercle The superior articular surfaces of both the lateral and medial condyles are concave particularly centrally. The outer margins of the surfaces are flatter and are the regions in contact with the interarticular discs (menisci) of fibrocartilage in the knee joint. The intercondylar region of the tibial plateau lies between the articular surfaces of the medial and lateral condyles. It is narrow centrally where it is raised to form the intercondylar eminence , the sides of which are elevated further to form medial and lateral intercondylar tubercles.

8. The intercondylar region bears six distinct facets for the attachment of menisci and cruciate ligaments. The anterior intercondylar area widens anteriorly and bears three facets: the most anterior facet is for attachment of the anterior end (horn) of the medial meniscus ; immediately posterior to the most anterior facet is a facet for the attachment of the anterior cruciate ligament ; a small facet for the attachment of the anterior end (horn) of the lateral meniscus is just lateral to the site of attachment of the anterior cruciate ligament.

9. The posterior intercondylar area also bears three attachment facets: the most anterior is for attachment of the posterior horn of the lateral meniscus ; posteromedial to the most anterior facet is the site of attachment for the posterior horn of the medial meniscus ; behind the site of attachment for the posterior horn of the medial meniscus is a large facet for the attachment of the posterior cruciate ligament.

10. Proximal end of fibula The fibula is the lateral bone of the leg and does not take part in formation of the knee joint or in weightbearing. It is much smaller than the tibia and has a small proximal head, a narrow neck, and a delicate shaft, which ends as the lateral malleolus at the ankle. The head of the fibula is a globe-shaped expansion at the proximal end of the fibula. A circular facet on the superomedial surface is for articulation above with a similar facet on the inferior aspect of the lateral condyle of the tibia. Just posterolateral to this facet, the bone projects superiorly as a blunt apex (styloid process).

11. patella The patella (knee cap) is the largest sesamoid bone (a bone formed within the tendon of a muscle) in the body and is formed within the tendon of the quadriceps femoris muscle as it crosses anterior to the knee joint to insert on the tibia. The patella is triangular. Its apex is pointed inferiorly for attachment to the patellar ligament, which connects the patella to the tibia Its base is broad and thick for the attachment of the quadriceps femoris muscle from above; Its posterior surface articulates with the femur and has medial and lateral facets, which slope away from a raised smooth ridge-the lateral facet is larger than the medial facet for articulation with the larger corresponding surface on the lateral condyle of the femur.

12. The following is a list of knee actions and the muscles that initiate them. • Knee flexion is executed by the biceps femoris, semitendinosus, semimembranosus, gracilis, sartorius, gastrocnemius, popliteus, and plantaris muscles. • Knee extension is executed by the quadriceps muscle of the thigh, consisting of three vasti—the vastus medialis, vastus lateralis, and vastus intermedius—and by the rectus femoris. External rotation of the tibia is controlled by the biceps femoris. The bony anatomy also produces external tibial rotation as the knee moves into extension. Internal rotation is accomplished by the popliteal, semitendinosus, semimembranosus, sartorius, and gracilis muscles. Rotation of the tibia is limited and can occur only when the knee is in a flexed position.

13. Joint Capsule The articular surfaces of the knee joint are completely enveloped by the largest joint capsule in the body Anteriorly, the joint capsule extends upward underneath the patella to form the suprapatellar pouch. The inferior portion contains the infrapatellar fat pad and the infrapatellar bursa. Medially , a thickened section of the capsule forms the deep portion of the medial collateral ligament. Posteriorly , the capsule forms two pouches that cover the femoral condyles and the tibial plateau.

14. Synovial membrane The synovial membrane of the knee joint attaches to the margins of the articular surfaces and to the superior and inferior outer margins of the menisci . Posteriorly, the synovial membrane reflects off the fibrous membrane of the joint capsule on either side of the posterior cruciate ligament and loops forward around both ligaments thereby excluding them from the articular cavity. Anteriorly, the synovial membrane is separated from the patellar ligament by an infrapatellar fat pad . In addition, the synovial membrane covering the lower part of the infrapatellar fat pad is raised into a sharp midline fold directed posteriorly (the infrapatellar synovial fold ), which attaches to the margin of the intercondylar fossa of the femur.

15. The synovial membrane of the knee joint forms pouches in two locations to provide low friction surfaces for the movement of tendons associated with the joint: the smallest of these expansions is the subpopliteal recess which extends posterolaterally from the articular cavity and lies between the lateral meniscus and the tendon of the popliteus muscle, which passes through the joint capsule; the second expansion is the suprapatellar bursa a large bursa that is a continuation of the articular cavity superiorly between the distal end of the shaft of femur and Thigh Synovial membrane of the knee joint and associated bursae.

16. Locking Mechanism When standing , the knee joint is locked into position, thereby reducing the amount of muscle work needed to maintain the standing position. One component of the locking mechanism is a change in the shape and size of the femoral surfaces that articulate with the tibia: in flexion , the surfaces are the curved and rounded areas on the posterior aspects of the femoral condyles; as the knee is extended , the surfaces move to the broad and flat areas on the inferior aspects of the femoral condyles.

17. Consequently the joint surfaces become larger and more stable in extension. Another component of the locking mechanism is medial rotation of the femur on the tibia during extension . Medial rotation and full extension tightens all the associated ligaments. Another feature that keeps the knee extended when standing is that the body's center of gravity is positioned along a vertical line that passes anterior to the knee joint.

18. Stabilizing Ligaments The major stabilizing ligaments of the knee are the cruciate ligaments, the collateral ligaments, and the capsular ligaments. The cruciate ligaments account for a considerable amount of knee stability. They are two ligamentous bands that cross one another within the joint capsule of the knee. The anterior cruciate ligament (ACL) attaches below and in front of the tibia; then, passing backward, it attaches laterally to the inner surface of the lateral condyle. The posterior cruciate ligament (PCL), the stronger of the two, crosses from the back of the tibia in an upward, forward, and medial direction and attaches to the anterior portion of the lateral surface of the medial condyle of the femur

19. Anterior Cruciate Ligament comprises three twisted bands: the anteromedial, intermediate, and posterolateral bands. In general, the anterior cruciate ligament prevents the femur from moving posteriorly during weight bearing and limits anterior translation of the tibia in non–weight bearing. It also stabilizes the tibia against excessive internal rotation and serves as a secondary restraint for valgus or varus stress with collateral ligament damage. When the knee is fully extended, the posterolateral section of the cruciate ligament is most tight. In flexion the posterolateral fibers loosen and the anteromedial fibers tighten. The anterior cruciate ligament works in conjunction with the thigh muscles, especially the hamstring muscle group, to stabilize the knee joint.

20. Posterior Cruciate Ligament Some portion of the posterior cruciate ligament is taut throughout the full range of motion. In general, the posterior cruciate ligament resists internal rotation of the tibia, prevents hyperextension of the knee, limits anterior translation of the femur during weight bearing, and limits posterior translation of the tibia in non–weight bearing. Capsular and Collateral Ligaments Additional stabilization of the knee is provided by the capsular and collateral ligaments. Besides providing stability, they also direct movement in a correct path. Although they move in synchrony, they are divided into the medial and lateral complexes.

21. Medial Collateral Ligament The superficial position of the medial (tibial) collateral ligament (MCL) is separate from the deeper capsular ligament at the joint line. It attaches above the joint line on the medial epicondyle of the femur and below on the tibia, just beneath the attachment of the pes anserinus. The posterior aspect of the ligament blends into the deep posterior capsular ligament and semimembranous muscle. Fibers of the semimembranous muscle go through the capsule and attach to the posterior aspect of the medial meniscus, pulling it backward during knee flexion. Its major purpose is to prevent the knee from valgus and external rotating forces.

22. Lateral Collateral Ligament and Related Structures The lateral (fibular) collateral ligament (LCL) is a round, fibrous cord that is about the size of a pencil. It is attached to the lateral epicondyle of the femur and to the head of the fibula. The lateral collateral ligament is taut during knee extension but relaxed during flexion. The arcuate ligament is formed by a thickening of the posterior articular capsule. Its posterior aspect attaches to the fascia of the popliteal muscle and the posterior horn of the lateral meniscus. Other structures that stabilize the knee laterally are the iliotibial band, popliteus muscle, and biceps femoris.

23. Bursae A bursa is composed of pieces of synovial tissue separated by a thin fi lm of fluid. The function of a bursa is to reduce the friction between anatomical structures. Bursae are found between muscle and bone, tendon and bone, tendon and ligament, and so forth. As many as two dozen bursae have been identified around the knee joint. The suprapatellar, prepatellar, infrapatellar, pretibial, and gastrocnemius bursae are perhaps the most commonly injured about the knee joint.

24. Sciatic nerve The sciatic nerve is a branch of the lumbosacral plexus (spinal cord segments L4-S3) and descends into the posterior compartment of thigh from the gluteal region ). In the posterior compartment of thigh, the sciatic nerve lies on the adductor magnus muscle and is crossed by the long head of biceps femoris muscle. Proximal to the knee, the sciatic nerve divides into its two terminal branches: the tibial nerve and the common fibular nerve . These nerves travel vertically down the thigh and enter the popliteal fossa posterior to the knee. Here, they meet the popliteal artery and vein. Nerve Supply

25. The tibial nerve innervates most of the hamstrings and the gastrocnemius. The common peroneal nerve innervates the short head of the biceps femoris and then courses through the popliteal fossa and wraps around the proximal head of the fibula. Because the peroneal nerve is exposed at the head of the fi bula, contusion of the nerve can cause distal sensory and motor deficits.

26. Leg Alignment Deviations That May Predispose to Injury Four major leg deviations could adversely affect the knee and patellofemoral joints: patellar malalignment, genu valgum (knockknees), Genu varum (bowlegs), and genu recurvatum(hyperextended knees). Patellar malalignment In patella alta, the patella sets in a more superior position than normal when the patient is standing. The ratio of patellar tendon length to the height of the patella is greater than the normal 1:1 ratio. In patella alta, the length of the patellar tendon is 20 percent greater than the height of the patella. In patella baja , the patella sets in a more inferior position than normal and the ratio of patellar tendon length to the height of the patella is less than the normal 1:1 ratio.

27. Medial Collateral Ligament Sprain Etiology Most knee sprains affect the MCL from either a direct blow from the lateral side in a medial direction (valgus force) or from lateral tibial rotation.

28. Lateral Collateral Ligament Sprain Sprain of the lateral collateral ligament of the knee is much less prevalent than sprain of the medial collateral ligament. Etiology The force required to tear this ligament is varus, often with the tibia internally rotated

29. Anterior Cruciate Ligament Sprain Etiology The anterior cruciate ligament sprain is generally considered to be the most serious ligament injury in the knee. The ACL is most vulnerable to injury when the tibia is externally rotated and the knee is in a valgus position. The ACL can sustain injury from a direct blow to the knee or from a noncontact single-plane force.

30. Posterior Cruciate Ligament Sprain The PCL has been called the most important ligament in the knee, providing a central axis for rotation. The PCL provides about 95 percent of the total restraining force to straight posterior displacement of the tibia. Etiology The PCL is most at risk when the knee is flexed to 90 degrees. A fall with full weight on the anterior aspect of the bent knee with the foot in plantar flexion or receipt of a hard blow to the front of the bent knee can tear the PCL

31. Meniscal Lesions The medial meniscus has a much higher incidence of injury than does the lateral meniscus The lateral meniscus does not attach to the capsular ligament and is more mobile during knee movement. Because of the attachment to the medial structures, the medial meniscus is prone to disruption from valgus and torsional forces. Etiology A valgus force can adduct the knee, often tearing and stretching the medial collateral ligament; meanwhile, its fibers twist the medial meniscus outward. Repeated mild sprains reduce the strength of the knee to a state favourable for a cartilaginous tear by lessening its normal ligamentous stability.

32. The most common mechanism is weight bearing combined with a rotary force while the knee is extended or flexed. If an individual makes a cutting motion while running, it can distort the medial meniscus. Stretching of the anterior and posterior horns of the meniscus can produce a verticallongitudinal, or “bucket-handle” tear. Another way that a longitudinal tear occurs is if the knee is forcefully extended from a flexed position while the femur is internally rotated.

33. During extension, the medial meniscus is suddenly pulled back, causing the tear. In contrast, the lateral meniscus can sustain an oblique tear by a forceful knee extension with the femur externally rotated. These oblique tears are sometimes referred to as “parrot beak” tears and occur in the inner periphery of the meniscus. A large number of medial meniscus lesions are the outcome of a sudden, strong internal rotation of the femur with a partially flexed knee while the foot is firmly planted. The force of this action pulls the meniscus out of its normal bed and pinches it between the femoral condyles. Meniscal lesions can be longitudinal, oblique, or transverse. Because of the blood supply of a meniscus, tears in the outer one-third of the meniscus may heal over time if stress in the area is a minimized.

34. Valgus force → medial collateral ligament rupture. If the force continues- medial meniscus injury and with further force ACL rupture Varus force → lateral collateral ligament injury Hyperextension force → ACL injury Fall on to flexed knee/ dashboard injury → PCL injury Forceful internal rotation → lateral meniscus injury Forceful external rotation → medial meniscus injury Hyperflexion (squatting) → meniscus injury (posterior horn)

35. INTRA ARTICULAR INJECTION

36. Bursitis Bursitis in the knee can be acute, chronic, or recurrent. Although any one of the numerous knee bursae can become infl amed, anteriorly the prepatellar, deep infrapatellar, and suprapatellar bursae have the highest incidence of irritation. Etiology The prepatellar bursa often becomes inflamed from placing pressure on the front of the knee while kneeling, and the deep infrapatellar bursa becomes irritated from overuse of the patellar tendon.

37. Symptoms and signs Prepatellar bursitis results in localized swelling above the knee that is ballotable. Swelling is not intraarticular, and there may be some redness and increased temperature. Swelling in the popliteal fossa could be a sign of a Baker’s cyst. A Baker’s cyst is associated with the semimembranosus bursa and occurs under the medial head of the gastrocnemius muscle. It is connected directly to the joint, and it swells because of a problem in the joint, not because of bursitis. A Baker’s cyst is commonly painless, causing no discomfort or disability. Some inflamed bursae may be painful and disabling because of the swelling and should be treated accordingly.

38. Localized Swelling Anterior aspect of the knee Prepatellar bursitis Infrapatellar bursitis Lateral aspect of the knee Lateral meniscal cyst Posteromedially Semimembranosus bursitis Posteriorly Baker’s cyst Popliteal aneurysm

39. Q Angle An angle found by drawing a line from ASIS to middle of patella and a second line from mid patella to tibial tuberosity Represents efficiency of Quads Males range from 10-14 Females from 15-17 Great than 17 degrees knock knees Very small angle causes genu varum

40. References Clinical Neuroanatomy, Snell’s Gray’s Anatomy Snell’s Anatomy