Knee Anatomy & Disorders
By : Nour Abu Al-Sha’ar
Knee Anatomy - The Knee Joint is the largest & most complicated joint in the body . - It consists of 3 Joints within a single synovial cavity : 1) Medial Condylar Joint : Between the medial condyle “of the femur” & the medial condyle “of the tibia” . 2) Latral Condylar Joint : Between the lateral condyle “of the femur” & the lateral condyle “of the tibia” . 3) Patellofemoral Joint : Between the patella & the patellar surface of the femur .
Types : - 1 & 2 : Hinge . - 3 : Planar gliding .
Anatomical Components of the Knee 1) Capsule : Surrounds the sides & posterior aspect of the joint… On the frontal side , the capsule is absent . On each side of the patella , the capsule is strengthened by the tendons of Vastus Lateralis & Vastus Medialis .
2) Ligaments : A] Extracapsular Ligaments : - Ligamentum Patellea ((a continuation of the Quariceps Femoris muscle )) - Lateral Collateral Lig. - Medial Collateral Lig. - Oblique Popliteal Lig (( derived from the Semimembranosus muscle )).
B ) Intracapsular Ligaments : Cruciate Ligaments : 2 strong ligaments that cross each other within the joint cavity . ~ Anterior Cruciate Ligament (ACL) : = Attached to the anterior intercondylar area of the tibia , passes upward , backward & laterally to get attached to the lateral femoral condyle . = Prevents posterior displacement of the femur (( With the knee joint flexed , the ACL prevents the tibia from being pulled anteriorly)) . ~ Posterior Cruciate Ligament (PCL) : =Attached to the posterior intercondylar area of the tibia , passes upward , forward , & medially to get attached to the medial femoral condyle . = Prevents anterior displacement of the femur (( With the knee joint flexed , the PCL prevents the tibia from being pulled posteriorly )) .
- The medial and lateral menisci are 2 C-shaped sheets of fibrocartilage between the tibial & femoral condyles - Their peripheral border is thick & attached to the capsule , their inner border is thin & forms a free edge . -
Each meniscus is attached to the upper surface of the tibia by anterior & posterior horns .
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They are connected to each other by the transversa ligament and to the margins of the head of the tibia by coronary ligaments.
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There are several differences between the medial and lateral meniscus, both anatomically (how they look) and functionally (how they work). Since the medial meniscus is attached to the joint capsule all around its outer edge, it does not slide much in any direction and is therefore more likely to tear. The lateral meniscus is more rounded, and there is a section where it is not attached to the joint capsule wall. Therefore it is more likely to move rather than tear.
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They increase the stability of the knee, control rolling and
One differentiates morphologically (= related to the cellular structure) : 1. The meniscus base, which is in immediate contact with the joint capsule (red zone) 2. The intermediate meniscus region (light red zone) 3. The white fringes.
Vessels penetrate through the red zone until the central third of the meniscus (designated as light red)… By contrast, the white fringe indicates no vessels. It is nourished via the joint fluid (= joint lubrication).
Thick, circular-triangular bone which articulates with the femur and covers and protects the anterior articular surface of the knee joint. It is the largest sesamoid bone .
Anterior surface It can be divided into three parts: The upper third is coarse, flattened, and rough; it serves for the attachment of the tendon of the quadriceps and often has exostoses. The middle third has numerous vascular canaliculi. The lower third includes the distal apex which serves as the origin of the patellar ligament. Posterior surface The upper three-quarters articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape.
It is attached to the tendon of the quadriceps femoris muscle, which contracts to extend/straighten the knee. The vastus intermedialis muscle is attached to the base of patella. Thevastus lateralis and vastus medialis are attached to lateral and medial borders of patella respectively. The knee is normally in slight valgus so there is a natural tendency for the patella to pulled to the lateral side when the quadriceps muscle is contracted The patella is stabilized by the insertion of vastus medialis and the prominence of the anterior femoral condyles, which prevent lateral dislocation during flexion. When injuries occur, all structures are simultaneously affected. These ligaments hold the patella in place during static and dynamic phases.
Innervation of the Knee Femoral Nerve : Common Peroneal
(( Fibular )) Nerve . Tibial Nerve .
Knee Movements - Flexion : these muscles produce flexion : Biceps femoris , Semitendinosus , Semimembranosus , Gracilis, Sartorius , Popliteus . ~ Flexion is limited by the contact of the back of the leg with the thigh .
Extension : by the Quadriceps femoris . ~ Extension is limited by the tension of all the ligaments of the joint . -
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Medial Rotation : by the Sartorius , Gracilis , Semtendinosus .
- Lateral Rotation : by the Biceps femoris .
OSTEOARITHRITIS
c/o: middle age patient complain of pain starts insidiously and increase slowly over time ( months and years ) aggravated by exertion and relieved by rest, with time relief is less and less complete. Stiffness :mainly after rest Symptoms follow an intermittent course with periods of remission lasts for months In advance stage : deformity ,swelling, muscle wasting and loss of mobility . No systemic manifestations in contrast to inf. diseases.
Osteoarthritis (OA) : a chronic inflammatory joint disorder in which there’s progressive softening & destruction of the articular cartilage , accompanied by new growth of cartilage and bone at the joint margins (osteophytes) and capsular fibrosis... leading to bone exposure & severe pain .
OA is the most common joint dis.
The knee is the most common site.
It can be primary or secondary : Usually it’s Primary (( Idiopathic )) & affecting both knee joints ((Bilateral)) . Secondary causes might be : Trauma , localized or metabolic diseases , mechanical factors , Bone Dysplasia , etc …
Secondary causes of OA A. Trauma
D. Endocrine
1. Acromegaly 1. Acute 2. Hyperparathyroidism 2. Chronic (occupational, sports) 3. Diabetes mellitus 4. Obesity B. Congenital or 5. Hypothyroidism
developmental
1. Localized diseases: LeggCalve-Perthes, congenital hip dislocation, slipped epiphysis 2. Mechanical factors: unequal lower extremity length, valgus/varus deformity, hypermobility syndromes 3. Bone dysplasias: epiphyseal dysplasia, spondyloepiphyseal dysplasia, osteonychondystrophy
C. Metabolic 1. Ochronosis (alkaptonuria) 2. Hemochromatosis 3. Wilson's disease 4. Gaucher's disease
E. Calcium deposition diseases 1. Calcium pyrophosphate dihydrate deposition 2. Apatite arthropathy
F. Other bone and joint diseases 1. Localized: fracture, avascular necrosis, infection, gout 2. Diffuse: rheumatoid (inflammatory) arthritis, Paget's disease, osteopetrosis, osteochondritis
G. Neuropathic (Charcot joints) H. Endemic 1. Kashin-Beck 2. Mseleni
I. Miscellaneous 1. Frostbite 2. Caisson's disease 3. Hemoglobinopathies
Risk factors: 1- age .
The likelihood of developing osteoarthritis increases with age. The disease is equally common among men and women aged 45-55 years. After age 55 years, the disease becomes more common in women.
2- Racial difference. Knee osteoarthritis appears to be more common in African American women than in other groups.
3- 2ndy cause e.g hx of trauma . 4- obesity. 5- family Hx. 1) 2) 3) 4)
Predisposing factors : Articular surface injury . Torn meniscus . Ligament instability . Preexisting deformity .
Pathogenesis OA results from a disparity between the stress applied to the articular cartilage & the ability of the cartilage to withstand that stress , due to : 1)Weakening of the articular cartilage ( genetic defect in collagen type ll or inflammatory disorder “RA” ) . 2) Increased mechanical stress in some parts of the articular surface . The abraded bone under a cartilage ulcer may take on the appearance of ivory (eburnation = the bony sclerosis which occurs at the areas of cartilage loss.). Growth of cartilage and bone at the joint margins leads to osteophytes (spurs), which alter the contour of the joint and may restrict movement
Appositional bone growth occurs in the subchondral region - seen radiographically - . -
Synovitis & thickening of the joint capsule may occur & further restrict movement Periarticular muscle wasting is common & may play a major role in symptoms . So , to summarize the cardinal features are: 1) Progressive loss of cartilage thickness . 2) Subarticular cyst formation and sclerosis. 3) Remodeling of the bone ends & osteophyte formation . 4) Synovial irritation (( Synovitis )) . 5) Capsular thickening & fibrosis . -
X-Ray Findings
1- narrowing of joint space. 2- subarticular cyst formation and sclerosis. 3- osteophyte formation. 4- evidences of 2ndry causes e.g. old fracture. The first two are restricted initially to the major load-bearing part of the joint but later the entire joint is affected.
Pre Op…
Post Op… THR
Management
- Early : 1) Relieve the pain : by using NSAIDs . 2) Joint mobility : by physiotherapy . 3) Reduce the load : by using a walking stick , soft medical shoes, weight reduction & avoid stressful activities . If symptoms increase despite conservative treatment some form of operative treatment may be needed such as joint debridement: removal of interfering osteophytes and cartilage tags and loose bodies realignment osteotomy
- Late : Surgical intervention : Total Knee Arthroplasty (TKA) : The primary indication for TKA is to relieve pain caused by severe arthritis . ~ Pain should be significant & disabling , especially during night . dysfunction of the knee is causing significant reduction in the patient's quality of life
