Knee

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Anatomy of the Knee

Bones

The knee joint is one of the largest and most complex joints in the body. It is constructed by 4 bones and an extensive network of ligaments and muscles.

The thigh bone (Femur), the shin bone (Tibia) and the kneecap (Patella) articulate through tibiofemoral and patellofemoral joints. These three bones are covered in articular cartilage which is an extremely hard, smooth substance designed to decrease the friction forces. The patella lies in an indentation of the femur known as the intercondylar groove. 

The smaller shin bone that runs alonside the tibia (Fibula) is not directly involved in the knee joint, but provides a surface for important muscles and ligaments to attach to. 

Menisci

There are two menisci in the space between the femoral and tybial condyles. They are crescent-shaped lamellae, each with anterior and posterior horn, and are triangular in cross section. The surface of each meniscus is concave superiorly, providing a congruous surface to the femoral condyles and is flat inferiorly to accompany the relatively flat tibial plateau. The horns of the medial meniscus are further appart and meniscus appears ‘C’ shaped, than those of the lateral one where meniscus appears more ‘O’ shaped. 

The menisci correct the lack of congruence between the articular surfaces of tibia and femur, increase the area of contact and improve weight distribtion and shock apsorption. They also help to guide and coordinate knee motion, making them very important stabilizers of the knee. 

The menisci are connected with the tibia by coronary ligaments. The medial meniscus is much less mobile during joint motion than the lateral meniscus owing in large part to its firm attachment to the knee joint capsule and medial collateral ligament (MCL). On the lateral side, the meniscus is less firmly attached to the joint capsule and has no attachment to the lateral collateral ligament (LCL). In fact, the posterior horn of the lateral meniscus is separated entirely from the posterolateral aspect of the joint capsule by the tendon of the popliteus muscle as it descends from the lateral epicondyle of the femur.

Menisci do not contain pain-sensitive structures and are consequently insensitive to trauma. Their outher third has some blood supply and therefore a slight ability to heal. The inner non-vascularized part receives nutrition through diffusion of synovial fluid.

The Joint Capsule

The joint capsule is a thick ligamentous structure that surrounds the entire knee. Inside this capsule is a specialized membrane known as the synovial membrane which provides nourishment to all the surrounding structures. The synovial membrane produces synovial fluid which lubricates the knee joint. Other structures include the infrapatellar fat pad and bursa which function as cushions to exterior forces on the knee. The capsule itself is strengthened by the surrounding ligaments. 

Ligaments 

The ligaments of the knee maintain the stability of the knee. Each ligament has a particular function in helping to maintain optimal knee stability.

1. Medial Collateral Ligament (MCL) - This band runs from the medial epicondyle of the femur to the medial condyl and the superior part of the medial surface of the tibia. In the middle of the ligament the deep fibers are attached to the medial meniscus. MCL resists forces acting from the outer surface of the knee, valgus forces.
2. Lateral Collateral Ligament (LCL) – a cord like ligament that begins on the lateral epicoondyle of the femur to the lateral surface of the fibula head. It resists impacts from the inner surface of the knee, varus forces.
3. Anterior Cruciate Ligament (ACL) - The ACL is one of the most important structures in the knee. The cruciate ligaments are so called because they form a cross in the middle of the knee joint. The ACL, runs from the anterior of the tibia to the posterior of the femur and prevents the tibia moving forward. It is most commonly injured in twisting movements.
4. Posterior Cruciate Ligament (PCL) - This ligament runs from the posterior surface of the tibia to the anterior surface of the femur and so wraps around the ACL. The PCL limits anterior rolling of the femur on the tibial plateau during extension.
   

Muscles and Tendons

The quadriceps muscle group is made up of four different individual muscles which join together forming the quadriceps tendon. This thick tendon connects the muscle to the patella which in turn connects to the tibia via the patella tendon. Contraction of the quadriceps pulls the patella upwards and extends the knee. The quadriceps muscles consist of the biceps femoris, vastus medialis, vastus intermedius and vastus lateralis muscles. The hamstring muscles at the back of the thigh function in flexing or bending the knee as well as providing stability on either side of the joint line. The hamstring muscles consist of the biceps femoris, semitendinosus and semimembranosus.

Muscles	Function	Periferal nerve	Spinal inervation
Quadriceps femoris	extension	Femoral	L2, L3, L4
Semitendinosus	flexion, internal rotation	Tibial	L5, S1, S2
Semimembranosus	flexion, internal rotation	Tibial	L5, S1, S2
Gracilis	flexion, internal rotation	Obturator	L2, L3, L4
Sartorius	flexion, internal rotation	Femoral	L2, L3
Popliteus	flexion, internal rotation	Tibial	L4, L5, S1
Tensor fasciae latae	flexion, internal rotation	Superior gluteal	L4, L5
Gastrocnemius	flexion, internal rotation	Tbial	S1, S2
Biceps femoris	flexion, external rotation	Sciatic	L5, S1

The two main muscle groups of the knee knee joint are the quadriceps and the hamstrings. 

• M. Quadriceps
• M. Biceps femoris
• M. Semimembranosus
• M. Semitendinosus
• M. Gracilis
• M. Sartorius
• M. Triceps Surae
• M. Plantaris

Function:

Motions Available:

Flexion and extension are the main movements. There is a little rotation when the knee flexes.

Range of motion

extension:0 degree                                                                 flexion:140

                                                  

Closed Packed Position:

Near full extension. There is a medial rotation of the femoral condyles on the tibial plateau.

Open Packed Position:

Midrange flexion.

Clinical Examination

• Knee Examination
• Special Tests
  • McMurray's Test
  • Apley's Test
  • Steinman's Test
  • Ege's Test
  • Ely's Test
  • LCL Test
  • MCL Test
  • Anterior Draw
  • Lachman Test
  • Pivot Shift
  • Slocum's Test
  • Posterior Drawer Test
  • Dial Test
  • Muller's Test
  • Patellar Apprehension Sign
  • Patellar Grind Test
  • Thessaly's Test

• Outcome Measures
  • Knee Injury and Osteoarthritis Outcome Score

Conditions

• Anterior Cruciate Ligament Injury
  
• Articular Cartilage Lesions
• Baker's Cyst
• Chondromalacia Patellae
  
• Femoral Fractures
• Hamstring Strain
• Iliotibial Band Syndrome
• Knee Osteoarthritis
• Knee Bursitis
  
• Lateral Collateral Ligament Injury
  
• Medial Collateral Ligament Injury
  
• Meniscal Lesions
• Ober's Test
• Osteochondritis Dissecans of the Knee
• Osgood-Schlatter's Disease
• Plica Syndrome
• Quadriceps Muscle Strain
• Quadricpes Muscle Contusion
  
• Patellofemoral Pain Syndrome
• Patellofemoral Instability
• Patellar Tendinitis
• Patellar Fractures
• Pes Anserinus Bursitis
• Plica Syndrome
• PrePatellar Bursitis
• Popliteus Tendinitis
• Posterior Cruciate Ligament Injury
  
• Sinding Larsen Johansson Syndrome
• Tibial Plateau Fractures

Procedures

• Arthroscopic Meniscectomy
• Meniscal Repair
• Articular Cartilage Debridement & Microfracture
• ACL Reconstruction
  • Patellar Tendon Autograph
    
  • Hamstring Tendon Autograph
    
  • Allograph
• PCL Reconstruction
• ORIF Post-Fracture
• Arthroscopic Debridement & Manipulation
• Lateral Release of the Patella
• Tibial Osteotomy
  

Interventions

• Therapeutic Exercise: Knee
• Manual Therapy: Knee
• ACL Rehabilitation
• Patellar Taping
  

Recent Related Research (from Pubmed)


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