The Knee Joint

Question 1

What are examples of acute injuries, chronic & acute swelling of the knee?

Answer 1

-Acute injuries= fracture, sports/fall, tear, sprain of ligament/soft tissue/cartilage
-Acute swelling= acute gout/flare, RA, septic joint
Chronic swelling= OA, bursitis

Question 2

Describe the knee joint

Answer 2

• Synovial
• Hinge joint
• 3 bones (distal femur, proximal tibia, patella)

Question 3

What articulations are formed at the knee?

Answer 3

• 2 femorotibial (medial & lateral)

- Femoropatellar

Question 4

What movements are possible at the knee joint?

Answer 4

• Flexion (loose some flexion when hip extended due to loss of tension on hamstring)
• Extension
• Medial & lateral rotation (only when the knee is flexed & collateral ligaments relaxed)

Question 5

What is ‘locking’ of the knee?

Answer 5

As joint approaches full extension femur medially rotates slightly on the tibia, very stable position so thigh muscles can relax

Question 6

How is the knee unlocked?

Answer 6

Popliteus muscle laterally rotates femur

Question 7

When is the knee joint weakest?

Answer 7

-Flexion
-Joint is incongruent
Tibial plateau is flat-poor fit to rounded femoral condyles

Question 8

What are menisci?

Answer 8

• 2 ‘C’ shaped wedges of fibrocartilage
• Thicker at external margins
• External edges attach to fibrous capsule of joint
• Deepen surface for femur to sit it
• Medial meniscus firmly attached to tibial collateral ligament

Question 9

What are the functions of the menisci?

Answer 9

• Increase joint congruency
• Distribute weight evenly
• Shock absorption
• Assist in locking mechanism

Question 10

How can meniscal tears occur?

Answer 10

• Due to sports injury or degenerative changes
• Displaced cartilage can become trapped during movement-painful locking
• Treat by repair or resection
• Damage associated with development of osteoarthritis

Question 11

Name the intra-articular and extra-articular ligaments of the knee

Answer 11

Intra-articular= anterior & posterior cruciate ligaments
Extra-articular= fibular & tibial collateral ligaments

Question 12

Describe the cruciate ligaments

Answer 12

• Inside the knee joint
• Cross obliquely
• ACL is weaker than PCL

Question 13

What are the attachments of the anterior cruciate ligament?

Answer 13

• Anterior intercondylar region of tibia

- Travels supero-posteriorly to attach to lateral femoral condyle

Question 14

What are the attachments of the posterior cruciate ligaments?

Answer 14

• Posterior intercondylar region of the tibia

- Travels supero-anteriorly to insert onto the medial femoral condyle

Question 15

What are the functions of the posterior cruciate ligament?

Answer 15

• Prevents posterior displacement of tibia
• Prevents hyperflexion
• Main stabiliser of the flexed knee when weight bearing
• Can be damaged when landing on tibial tuberosity with flexed knee

Question 16

What are the functions of the anterior cruciate ligament?

Answer 16

• Prevents anterior displacement of the tibia on the femur
• Prevents hyperextension
• ACL injury occurs when knee is hyperextended or force applied anteriorly

Question 17

Describe the Tibial collateral ligament

Answer 17

• Flat band attached to medial meniscus and medial margin of tibia
• Prevents abduction of the leg at the knee & rotation during extension of the knee

Question 18

Describe the location and action of fibular collateral ligament

Answer 18

• Cord like band
• Prevents adduction of the leg at the knee & rotation during extension of the knee
• Lateral femoral epicondyle to inferior fibular head

Question 19

What is an unhappy triad injury?

Answer 19

• Caused by excessive lateral twisting of flexed knee or blow to lateral side of extended knee
• Abduction tears tibial collateral ligament & medial meniscus
• Rotation ruptures ACL

Question 20

What muscles act on the knee joint?

Answer 20

• Quadriceps
• Hamstring (post. thigh)
• Gracilis
• Sartorius
• Iliotibial tract
• Main stabilisers of the knee

Question 21

How can the patella be dislocated?

Answer 21

• More common in females
• Rectus femoris, Vastus intermedius, Vastus lateralis all pulling superolaterally
• Counteracted by more horizontal pull of vastus medialis

Question 22

What abnormal alignments of the knee can occur?

Answer 22

• Genu varum= bow leg (tibia adducted wrt femur)

- Genu valgum= knock knee (tibia abducted wrt femur)

Question 23

What muscles are responsible for medial & lateral rotation of the knee?

Answer 23

• M=Gracilis, sartorius, popliteus, semitendinosus/membranosus
• L= Biceps femoris