Knee joint

Question 1

What are the three mechanisms responsible for knee injury?

Answer 1

1. Overuse injuries, often associated with coexisting predisposing factors like genu valgus, varus or recurvatum
2. Twisting or explosive movements as occur in basketball and soccer
3. Direct blows to the knee joint

Question 2

Describe the functional anatomy of the knee:

Answer 2

• consist of tibiofemoral and patellofemoral joints.
• joint between the lateral and medial condyles of the distal femur and the lateral and medial condyles of the proximal end of the tibia
• patella, a sesamoid bone within the quadriceps tendon (protects the tendon as it moves across the knee joint and acts as a pulley to increase mechanical leverage)
  tibial tuberosity, the insertion of the patella ligament
• fibula head which articulates with the lateral tibial condyle.
  -A modified hinge joint
• Main function is to maintain upright stance with as little energy expenditure as possible, allow shock absorption, conservation of energy and transmission of of forces through the lower limb.
• This is achieved by the locking mechanism of the knee and its supporting ligaments.
• stability depends solely on its soft tissue constraints rather than its bony configuration.
• When the femur medially rotates on the tibia during the final stages of extension:
  articulating surfaces are in greatest contact
  supporting ligaments are taut
• This is the close packed position. The knee is tight and stable and minimal muscle contraction is required to maintain upright stance.

Question 3

What are the motions of the knee?

Answer 3

• flexion/extension
• internal/external rotation: rapid change of direction.
  Note: rarely occur independently.

Question 4

Name the intra-capsular ligaments, insertion and function:

Answer 4

Anterior cruciate ligament: from the anterior intercondylar area of the tibia to the medial surface of the lateral femoral condyle. Prevents anterior movement of the tibia on the femur or posterior movement of the femur on the tibia. Resist extension and extremes of varus, valgus, and axial rotation.

Posterior cruciate ligaments: from posterior intercondylar area of the tibia to the lateral surface of the medial femoral condyle, prevents posterior movement of the tibia on the femur or anterior movement of the femur on the tibia. Resist flexion and extremes of varus, valgus and axial rotation.

Question 5

What are the common mechanisms of injuries for ACL/PCL:

Answer 5

ACL: Hyperextension with strong quadriceps contraction with the knee. Hamstring cannot counter act the hyperextension due to mm imbalance within the quads in addition weak gluteus can be a factor. Large valgus producing force or axial rotation torque with the foot firmly planted to the ground.Basket ball: jump, bad reception pop sound.

runs from the anterior part of the intercondylar area of the tibial plateau to the medial side of the lateral femoral condyle

a primary knee stabiliser preventing forward displacement of the tibia on the femur (or preventing the femur slipping backwards on the tibia)

anterior cruciate ligament sprains are relatively common, especially during excessive loads incurred during sharp deceleration, deceleration before a change in direction, or from landing from a jump or other activity

occur more often to women than men, possibly due to the role of oestrogen in ligamentous relaxation and their greater Q angle. Other predisposing factors include narrowness of the intercondylar notch, weak hamstrings relative to quadriceps, and pes planus.

PCL: Falling with ankle fully plantar flexes such that the proximal tibia hit the ground first.

Any event causing forceful translation of the tibia or anterior translation of the femur while knee flexes. Large axial rotation or valgus varus applied torque to the knee with foot firmly applied to the ground. Hyperextension. Skiing accident.

runs from the back of the intercondylar area of the tibia to the front of the intercondylar fossa of the femur
Sprains of the posterior cruciate are much less common than anterior cruciate ligament or medial collateral ligament
usually injured by a direct blow to the tibia, often when the knee is bent (e.g. dashboard injury) or by falls that hyperflex the knee

Patients report a sense of popping or giving way

The posterior cruciate ligament is mostly extracapuslar, has a good blood supply and good healing capacity

Question 6

What are the coronary ligaments:

Answer 6

Coronary ligaments are extensions of fibrous capsule that attach the menisci to the tibia

Transverse ligament which runs between the anterior horns of the two menisci

The coronary ligaments of the knee (also known as meniscotibial ligaments) are portions of the joint capsule which connect the inferior edges of the fibrocartilaginous menisci to the periphery of the tibial plateaus.

Question 7

What are the extra-capsular ligaments:

Answer 7

Medial collateral ligament: from medial epicondyle of femur to medial tibial condyle; composed of three groups of fibers, one connecting the two bones, and two fused with the medial meniscus; partly covered by pes anserine muscles; tendon of semimembranosus passes underneath. resists valgus, knee extension, extremes axial rotation.

Lateral collateral ligament: from lateral epicondyle of femur to head of fibula; separated from the joint capsule and the lateral meniscus by bursar. resists varus, knee extension, extremes axial rotation.

Question 8

What are the common injuries of MCL and LCL:

Answer 8

MCL: severe hyperextension, valgus producing force with foot planted to the ground. the larger of the two collateral ligaments

function is to enhance medial stability of the knee

runs from the medial epicondyle to the medial side of the tibia about 2.5cm below the condyle, just posterior to the pes anserine insertion (the common insertion of sartorius, gracilis and semitendinosus)
Its deep part is firmly attached to the medial meniscus.

injury to the medial collateral ligament may cause damage to the joint capsule and damage to the medial meniscus
(The lateral collateral ligament is not connected to the joint capsule or the lateral meniscus and injuries to this ligament are rarely as severe as injuries to the medial collateral ligament.)

The pes anserine muscles cross over the lower part of the medial collateral ligament; separated from it by the pes anserine bursa

LCL: Varus-producing force with foot planted to the ground or severe hyperextension.

Question 9

Give briefly the function (biomechanics) of the distal femur, tibia and fibula:

Answer 9

• Distal femur: passage for the cruciate ligaments but also serve as elevated attachment sites for the collateral ligaments due to its condyle shape. Lateral intercondylar groove facet help stabilise the patella during knee movement. when the knee is fully extended, the tibia is aligned with the intercondylar grooves giving the visual asymmetry of the knee and the shape of the lateral and medial aspect of the articular surfaces of the femur.
• Fibula: no direction function at the knee, and helps only in alignment . It serves as attachment for the biceps femurs and the lateral collateral ligament and the lateral side of the tibia by proximal and distal tibiofibular joint.
• Tibia: function is to transfer weight across knee and the ankle.

Question 10

Give the characteristics of menisci:

Answer 10

• two fibrocartilaginous discs cover the surface of tibial condyles
• improve the conformity of the articulating surfaces
• cushion the joint
• lateral meniscus is oval-shaped; thicker, shorter and more mobile than the medial meniscus
• medial meniscus is C-shaped; thinner, larger, less mobile because of its attachment to the medial collateral ligament.
• primary function: reduce the compressive stress across the tibiofemoral joint. Stabilising function of the joint during motion, lubricating the articular cartilage, providing proprioception and guide the knee arthrokinematics.
• common injury occurs due to tears of menisci, take time to heal due to poor blood supply. can generate imbalance in gait due to force uneven affect hip joint and lower back.
• medial meniscus injured twice as frequently as the lateral common to look for medial collateral ligaments.
• Neumann: compression forces at the knee joint reach 2.5 to 3 times the body weight while one is walking, over 4 times body weight while ascends stairs. the menisci reduce this pressure force.
• both menisci move posterior with the lateral one 10mm .

Question 11

Named the most important Bursa:

Answer 11

20+ associated with the knee

Most important
Prepatellar bursa which overlies the patella below the skin
Infrapatellar bursa between superior part of tibia and patellar ligament
Pes anserine bursa
Iliotibial band bursa
Inferior subtendinous bursa of biceps
Suprapatellar bursa between inferior part of femur and the quadriceps femoris muscle; communicates directly with the knee joint muscle
Popliteal bursa behind the knee joint

Question 12

Explain the relationship between the synovial membrane, bursar and fat pads:

Answer 12

Internal surface of the knee = synovial membrane.

Bursar forms at inter tissue junction that encounter high force of friction during movement involving tendons, ligaments, skin, bone, capsule and muscle.

Some bursae are simple extensions of the synovial membrane and others are formed external to the capsule.

Fat pads are associated with bursar around the knee. The combination of the fat pads and the synovial fluid reduce friction between the moving structures.

Question 13

What is the joint capsule:

Answer 13

• Largest in body
• Surrounds entire joint, except anteriorly
  joint capsule (capsular ligament) encloses the patella, ligaments, menisci and bursar
• consists of a synovial and fibrous membrane separated by fat pads

Question 14

Named the muscles that move the knee joint:

Answer 14

Prime movers
quadriceps (knee extensors) and hamstrings (knee flexion)

Popliteus
main function is to unlock the extended (weight-bearing) knee; it laterally rotates the femur on the tibia and moves the lateral meniscus posteriorly at the beginning of knee flexion.
external rotation when the knee is semi-flexed is a function of biceps femoris
popliteus medially rotates the tibia when the knee is flexed along with sartorius, gracilis and semitendinosus

Question 15

Posterior capsule of the knee:
What it is? Give some features:
Anatomy, clinically:

Answer 15

The popliteus muscle unlock the knee and serves during weight bearing. The popliteus muscle runs diagonally across the back of the knee joint. This muscle rotates the lower leg and plays a role in bending (flexing) the knee. The popliteus muscle helps to stabilize the back and outer back of the knee and is most often injured in downhill skiing and long-distance running. [1B] A M. Popliteus strain is a muscle strain.

The different diagnoses for posterior knee pain include pathology to the bones, musculotendinous structures, ligaments, and/or to the bursas. Less common are neurologic and vascular injuries. However peripheral nerves changes can suggest a nerve entrapment due to popliteus hypertonicity. Also tumors, such as a begin tumor that contains both bone and cartilage and usually occurs near the end of a long bone (osteochondroma) or bony tumors. Tenderness of palpation over the tendons or muscles in the back of the knee can indicate muscle or tendon injury. Pain or swelling in the popliteal area suggests an effusion or cyst.

The semimembranosus tendon is a part of the posteromedial joint capsule, which is important in controlling anteromedial rotatory instability. (Together with the pes anserinus tendons it gives medial and posteromedial reinforcement.)[3] There is a U-shaped bursa that surrounds the distal SM tendon, separating it from the medial-tibial plateau, medial (tibial) collateral ligament (MCL), and semitendinosus tendon (surrounding structures).

The simple presence of the surrounding anatomical structures causes increased friction to the SM tendon (and irritation to the bursa) during repetitive knee flexion.

Semimembranosus tendinopathy (SMT)
This is an uncommon cause of chronic posteromedial knee pain that more often occurs with older patients. It may be underdiagnosed or inadequately treated because of a lack of understanding of the condition. But timely diagnosis can lead to effective treatments. 
Although tendinopathy may occur in any of the hamstrings tendons, the semimembranosus tendon is the most commonly affected.  It may occur as a primary phenomenon in endurance athletes or as a secondary, overuse, compensatory condition from a primary knee abnormality, such as patellofemoral disorders.[4] 
SMT usually presents as an aching pain localized to the posteromedial knee with tenderness on palpation inferior to the joint.[1] The pain is severe in its acute form, but symptoms increase with activities that involve significant hamstring activation: running, cycling, walking down stairs, climbing, or sudden deep knee flexion.[5][6] 

• Hamstring Strain (HSS)
Characteristics of hamstring strain.
Main symptoms are, a sudden sharp pain during sport activities, it can also be described as a tearing impression, and tightness, weakness and impaired range of motion.

Question 16

What are the structure of the popliteal fossa and important characteristics about it:

Answer 16

Tibial nerve, popliteal artery and vein. Can generate nerve entrapment, insufficient blood flow to lower limb or poor venus return due to hypertonicity of popliteus, weak gastrocnemius.

Question 17

What is baker cyst?

Answer 17

A Baker’s cyst is a pocket of fluid that forms a lump behind the knee. It is also called a popliteal cyst.

A Baker’s cyst is caused when excess joint fluid is pushed into one of the small sacs of tissue behind the knee. When this sac fills with fluid and bulges out, it is called a cyst. The excess fluid is usually caused by conditions such as rheumatoid arthritis or osteoarthritis that irritate the knee. It may also be caused by an injury or repetitive knee flexion.

Often a Baker’s cyst causes no pain. When symptoms occur, they may include:

Tightness or stiffness behind the knee.
Swelling behind the knee that may get worse when you stand.
Slight pain behind the knee and into the upper calf. You are most likely to feel this when you bend your knee or straighten it all the way.

Sometimes the pocket of fluid behind the knee can tear open and drain into the tissues of the lower leg. This can cause swelling and redness in that part of the leg.

Question 18

Named the structure that limits excessive movement during knee flexion, extension and co-contraction of muscles:

Answer 18

Knee flexion – limited by anterior and posterior cruciates, posterior horns of the menisci, and quadriceps

Knee extension – limited by anterior and posterior cruciates, posterior joint capsule, the anterior horns of the menisci, and hamstrings

Co-contraction of knee muscles – in many activities of daily living, hamstrings contracts with the quadriceps (hamstrings exert posterior shear force on tibia and reduce force on ACL when knee is flexed)

Question 19

What is the nerve supply of the leg and muscles associated with the knee:

Answer 19

femoral nerve innervates the quadriceps and sartorius muscle
sciatic nerve innervates the hamstrings and popliteus (tibial)
obturator nerve innervates gracilis

Question 20

What are the special tests for the knee?

Answer 20

Special tests
Patella: patellofemoral grind (incl. Clarke’s), apprehension test (Fairbank’s)
Ligaments: anterior/posterior draw, valgus/varus stress
Meniscus: Apley’s compression and grind, McMurray’s test

Question 21

Case history: what are the reflection you would have about the knee.

Answer 21

Identify red and yellow flags

Does the pain have a mechanical cause?
Is the pain associated with rest or activity, certain postures or time of day?
e.g. morning pain relieved with daily activity is often associated with arthritis

Obtain descriptions of the specific mechanism of the injury and the forces involved

weight bearing at the time of injury?

valgus or varus stress or rotation force at the time of injury?

contact with the ground or an opponent?

a sound or pop/shift in the knee? (A pop is often associated with a torn anterior cruciate ligament; a shift can occur with anterior cruciate ligament rupture or patella dislocation)

What happened after the injury?
Collapse, inability to continue playing, inability to weight bear suggest fracture or serious ligament injury

Did the knee swell and, if so, how quickly did it occur? (Swelling in the first hour suggests haemarthrosis from ruptured cruciate ligament or fracture: swelling developing more slowly suggests traumatic synovitis associated with meniscal tears and chondral pathology)

Did the knee click, lock or is it unstable? (Painful clicking suggests meniscal tear or chondral pathology.)

Determine if the client has a history of gout, pseudogout, rheumatoid arthritis or degenerative joint disease

Any evidence of neurologic compromise (e.g. change in cutaneous sensation, weakness of foot/toe muscles) or vascular compromise

Question 22

What is the pathophysiology of Gout:

Answer 22

Gout and pseudogout are the 2 most common crystal-induced arthropathies. Gout is caused by monosodium urate monohydrate crystals; pseudogout is caused by calcium pyrophosphate crystals and is more accurately termed calcium pyrophosphate disease. Gout can be considered a disorder of metabolism that allows uric acid or urate to accumulate in blood and tissues. When tissues become supersaturated, the urate salts precipitate, forming crystals. In addition, the crystals also are less soluble under acid conditions and at low temperatures, such as occur in cool, peripheral joints (eg, the metatarsophalangeal joint of the big toe).
Urate initially precipitates in the form of needlelike crystals. The presence of urate crystals in the soft tissues and synovial tissues is a prerequisite for a gouty attack. However, these crystals can also be found in synovial fluid or on the cartilage surface in the absence of joint inflammation.

Physical findings may include the following:
Involvement of a single (most common) or multiple joints
Signs of inflammation – Swelling, warmth, erythema (sometimes resembling cellulitis), and tenderness
Fever (also consider infectious arthritis)
Migratory polyarthritis (rare)
Posterior interosseous nerve syndrome (rare)
Tophi in soft tissues (helix of the ear, fingers, toes, prepatellar bursa, olecranon)
Eye involvement – Tophi, crystal-containing conjunctival nodules, band keratopathy, blurred vision, anterior uveitis (rare), scleritis.

Question 23

What would be an important factor to look at during physical examination:

Answer 23

Observe Q-angle, genu valgus, genu varum, genu recurvatum and tibial torsion. Q-angle : angle between a line from the ASIS to the middle of the patella and a line from the middle of the patella to the tibial tubercle. In males, the Q-angle is approximately 14 and in females 17
If the Q angle exceeds 15 to 20° (slightly more in females), the patella is likely to track laterally causing it to rub against the lateral femoral condyle.

level of the popliteal creases can indicate leg length.

Question 24

Give the definition of bowed legs, knock knees and back knee:

Answer 24

Gene varum (bowed knee): frontal deviations of the knee with excessive angle more than 180- degree.

Gene valgum (knock knee): excessive deviations angle inferior than 165 degree.

Normal knee angle is 125 degree of inclination.

Genu recurvatum: a deformity in the knee joint, so that the knee bends backwards. In this deformity, excessive extension occurs in the tibiofemoral joint. Genu recurvatum is also called knee hyperextension and back knee. This deformity is more common in women[citation needed] and people with familial ligamentous laxity.[2] Hyperextension of the knee may be mild, moderate or severe.

The normal range of motion (ROM) of the knee joint is from 0 to 135 degrees in an adult. Full knee extension should be no more than 10 degrees. In genu recurvatum (back knee), normal extension is increased. The development of genu recurvatum may lead to knee pain and knee osteoarthritis.

Question 25

Functional testing of the knee:

Answer 25

Combining tests seems to be useful for identifying and ruling out various knee conditions
anterior draw test is useful for identifying anterior cruciate ligament tears
valgus and varus tests are fairly good at ruling out medial collateral ligament tears
patella apprehension test appears to be good at identifying and ruling out patella instability

Question 26

What are the commons conditions of the knee:

Answer 26

Muscle strains (hamstrings, quadriceps)
DJD
Patellofemoral pain syndrome
Patella dislocation
Ligament sprains
Meniscal injury
Bursitis

Question 27

Muscle strains, give two examples that affect the knee:

Answer 27

Quadriceps tendonitis at the knee

(1) tenoperiosteal junction at the superior aspect of the patella
(2) infrapatella tendon (jumper’s knee)
(3) the quadriceps expansion

Patient presents with pain at the front of the knee after excessive or sudden contraction of the quadriceps (e.g. running, hiking, dancing, squats or repetitive deep knee bends in weight lifting)

Hamstrings tendonitis at the knee

Common muscle strain in activities and sports that involve excessive eccentric contraction of the hamstrings such as running, kicking and dancing.

Vulnerable to strain when it is eccentrically contracting to fully extend the knee at heel strike, particularly when a fuller or more intense stretch than usual is required (e.g. running on slippery or hilly surfaces)

Ankle pronation and hip anteversion may predispose

Pain is felt at the medial or lateral tenoperiosteal insertions of the hamstring muscles either side of the knee

Question 28

What is the iliotibial band syndrome:

Answer 28

Overuse syndrome that leads to inflammation of the distal ITB near the lateral femoral condyle +/- the bursa between the ITB and the condyle

At full knee extension the ITB is anterior to the lateral condyle; when the knee is flexed to 30° or more, the ITB moves posterior to the condyle

Inflammation related to excessive running or cycling as ITB rubs over the lateral condyle

Question 29

What is the terrible triad?

Answer 29

The terrible triad (or unhappy triad)
anterior cruciate ligament, the medial collateral ligament and the medial meniscus - named because of the frequency with which these structures were injured together from a single injury, usually involving a strong valgus or rotary force to the knee
The new unhappy triad (anterior cruciate and medial collateral ligaments and the lateral meniscus) has been found to occur more frequently in athletes than the originally described triad

Question 30

What is the patellofemoral pain syndrome:

Answer 30

A number of factors play a role in the development of patellofemoral pain syndrome:

large Q angle - one of the most common factors that lead to patellar tracking disorders

Vastus medialis obliquus, the distal portion of the vastus medialis muscle, counterbalances the lateral pull of the other quadriceps. Imbalances between the strength of the vastus medialis obliquus, vastus lateralis and ITB band, with its lateral patellar expansion, contribute to tracking disorders.

Intrinsic factors such as patella alta (a hypermobile and unstable patella that is displaced proximally) and patella baja (the patella displaced distally so that the articular surfaces are incongruent) may be involved

C/O anterior knee pain aggravated by activities like ascending or descending stairs or squatting
knee pain on standing after a prolonged period of sitting (the movie sign)
sometimes the knee gives way (reflex muscular inhibition in response to strong pain sensation in the knee extensors)(26)

Question 31

What is a patella dislocation:

Answer 31

occurs when the patella moves laterally onto the lateral femoral condyle
usually the result of a twisting injury, such as sudden turning in football sports
often reduces spontaneously
predisposing factors include femoral anteversion, shallow femoral groove, genu valgus, loose medial retinaculum, tight lateral retinaculum, congenital absence of vastus medialis, increased Q angle, and excessive subtalar pronation
client often reports a sensation of something popping out in the knee, severe pain and an episode of instability(7)

Question 32

Meniscal injuries:

Answer 32

menisci may be damaged by trauma or degeneration
compressive forces can break, chip or tear the meniscus
tensile forces such as acute valgus injury can tear the meniscus
medial meniscus involved in 75% of meniscal injuries, particularly the posterior horn (medical meniscus attached to the deep fibres of the medial collateral ligament which restricts its movement)
Pieces of meniscus become separated and cause the knee to lock from time to time as they move around the joint
If a meniscus is removed or severely damaged, DJD often follows

Question 33

Bursitis

Answer 33

Bursitis can arise from friction with repetitive motion or direct trauma
Five common sites where bursitis occurs in the knee are the prepatellar bursa, pes anserine bursa, gastrocnemius bursa, popliteal bursa and iliotibial band bursa

Prepatellar bursitis
Prepatellar bursitis (housemaid’s knee) is common

A painless or slightly painful swelling localised over the anterior aspect of the patella and the patella tendon
If red, significantly tender or a nearby break in the skin must be aspirated to rule out infection

Usually from prolonged kneeling, kneeling on a hard surface or from direct trauma from a fall