Week 4 - G - Knee (1) - Knee arthritis / replacements, Osteochondral and extensor injury, patellorfemoral dysfunction/instability

Question 1

What does the knee joint consist off?

Answer 1

The knee joints consists of 2 tibiofemoral articulations (medial and lateral) and one patellofemoral articulation

Although these “joints” are often considered separately, they all communicate with each other as one synovial “knee” joint.

Question 2

The surfaces of the knee joints are covered with hyaline cartilage What is a niche fact about the hyaline cartilage lining the retropatellar surface?

Answer 2

The retropatellar surface has the thickest hyaline cartilage in the body - a reflection of the load placed on the patella; especially when descending the stairs

Question 3

The tibiofemoral joint contains the fibrocartilaginous menisci What are the different functions of the menisci?

Answer 3

The menisci are the intra-articular wedges of fibrocartilage in the knee joints Function

* Stabilise the knee joint

* Act as shock absorbers of the knee joint

* Assist in lubrication of the knee joint

* Deepen the articular surfaces of the knee joint

* Participate in the weight bearing of the knee joint

Question 4

What are the four main ligaments of the knee joint?

Answer 4

The anterior cruciate ligament

The posterior cruciate ligament

The medial collateral ligament

The lateral collateral ligament

Question 5

What is the principle role of the cruciate ligaments of the knee joint?

Answer 5

Principle role ACL - prevent abnormal internal rotation of the tibia and prevents the femur sliding posteriorly on the tibia

(ACL prevents Anterior translation of tibia onto the femur)

PCL - prevents the femur sliding anteriorly onto the tibia

(PCL revents Posterior translation of the tibia onto the femur (prevents hyperextension)

Question 6

How are the ACL and PCL tested?

Answer 6

ACL tested by assessing anterior translation of the tibia (anterior drawer test)

PCL tested by assessing posterior translation of the tibia (Posteiror drawer test)

Question 7

What is the function of the collateral ligaments of the knee?

Answer 7

The medial collateral ligaments resists valgus force (limits abduction of the tibia at the knee joint)

The lateral collateral ligament resists varus force (limits adduction of the tibia at the knee joint) and resists abnormal external rotation of the tibia

Question 8

What are potential risk factors which may predispose to early osteoarthritis of the knee?

Answer 8

May be predisposed by

* Previous meniscal tears

* Ligament injuries (especially ACL deficiency)

* And malalignment

Question 9

Does genu varum or valgum cause a medial or lateral OA of the knee joint? Explain why

Answer 9

Genu varum - medial OA of the knee joint

* the distal ends of the tibia are closer to one another as the person is bowlegged - this means the medial aspects of the knee are in closer contact with one another

Genu valgum - lateral OA of the knee

* distal ends of the tibia are further from one another as the person is knock kneed - this means the lateral aspects of the knee are in closer contact with one another

Question 10

Many cases of OA are “primary” OA with no obvious causative factor. Primary knee OA may have genetic influences and hobbies (eg football, distance running) or occupation may play a role however this has not been conclusively proven. Patellofemoral dysfunction and instability predispose to the development of patellofemoral OA. * For younger patients with OA isolated to medial compartment of the knee, what may be the choice of treatment? * Whcih workers may this be particularly useful for?

Answer 10

Younger patients with OA isolated to the medial compartment, particulary in varus knees may benefit from an oesteotomy of the proximal tibia - known as a high tibital osteotomy (HTO) to shift load to lateral compartment

Particularly useful for heavy manual workers, as a knee replacement would fail early if subject to heavy work

Question 11

What is the downside of high tibital osteoeomies?

Answer 11

The results of osteotomy are less predictable than knee replacement and benefit only last max 10 years

Question 12

Knee replacement can be considered in a patient with substantial pain and disability where conservative management is no longer effective. What are the two different types of knee replacements?

Answer 12

Total knee replacement (TKR) -

* resurfaces of all three compartments of the knee

Partial knee replacement (can be unicompartmenral knee replacement (UKR) or patellofemoral replacement) -

* resurfaces one compartment of the knee

Question 13

When are unicompartmental knee replacements proposed? When are patelloremoral replacements proposed?

Answer 13

UKR has been proposed as a potential treatment for patients with isolated OA of the medial or lateral compartment as a less invasive surgery with less bone removal and preservation of the knee ligaments.

It has been advocated particularly for use in the younger patient.

Patellofemoral replacement has been proposed for isolated PFJ OA.

Question 14

TKR is a surface replacement with short stems or no stems used. Most components are cemented. The risks of surgery are similar to hip replacement Between total hip replacements (THR) and total knee replacements (TKR), which has a higher ris of pain after and which has a higher risk of dislocation?

Answer 14

Total hip replacements have a higher risk of joint dislocation

Total knee replacements have a higher chance of unexplained pain after the surgery

Question 15

An osteochondral injury is an injury to the smooth surface on the end of bones, called articular cartilage (chondro), and the bone (osteo) underneath it. What do osteochondral injuries occur due to?

Answer 15

Osteochondral injuries occur due to impaction or shear of the articular surfaces or due to a direct blow

Question 16

Ongoing pain and effusion after a knee injury warrants further investigation - could possibly be an osteochondral injury What would be used to assess the knee?

Answer 16

Xray, MRI and arthroscopy are used to assess the knee

Question 17

How are acute injuries involving osteohondral fragments treated? (large vs small - try remember osteochondiritis dissecans treatment)

Answer 17

Acute injuries involving large osteochondral fragments with a substantial proportion of bone should be fixed with pins

If they are small, arthroscopic removal of the bone fragments may be carried out

Question 18

The defect in the surface of the knee due to osteochondral injuries may fill in with fibrocartilage (scar type hyaline cartilage) which is not as good as hyaline cartilage but performs a reasonable job If the defect has bare bone at its base, what can be done as treatment of the injury?

Answer 18

If a defect has bare bone at its base it can be drilled or holes made to induce bleeding (known as microfracture) to promote fibrocartilage formation from stem cells differentiating into chondroblasts.

Question 19

Which five things contribute towards the extensor mechanism of the knee?

Answer 19

Quadriceps muscles

Quadriceps tendon

Patellar Patellar tendon

Tibial tuberosity

Question 20

How can patellar tendon or quadriceps tendon ruptures occur?

Answer 20

The patellar tendon or quadriceps tendon can rupture with rapid contractile force which can occur after lifting a heavy weight, after a fall or spontaneously in a severely degenerate tendon

Question 21

What age group do patellar tendon ruptures occur in vs quadricepts tendon ruptures?

Answer 21

The patellar tendon or quadriceps tendon can rupture with rapid contractile force which can occur after lifting a heavy weight, after a fall or spontaneously in a severely degenerate tendon

Question 22

What age group do patellar tendon ruptures occur in vs quadriceps tendon ruptures?

Answer 22

Typically

* Patellar tendon ruptures occur in a younger age group 40

Question 23

What are predisposing factors for the extensor mechanism of the knee ruptures? What drugs predispose?

Answer 23

History of Tendonitis

Chronic steroid use or abuse

Diabetes

Rheumatoid arthritis

Chronic renal failure

Quinolone antibiotics (eg cirpofloxacin)

can cause tendonitis and can risk tendon ruptures

Question 24

Should steroid injections be given for tendontiis of the extensor mechanism of the knee?

Answer 24

Steroid injections for tendonitis of the extensor mechanism of the knee should be avoided due to high risk of tendon rupture (same as for achilles tendonitis)

Question 25

What test do you do to test the extensor mechanism of the knee? What examination is it carried out in?

Answer 25

This would be a straight leg raise Carried out in a knee examination

Question 26

What investigation would diagnose an extensor mechanism rupture? What is seen?

Answer 26

Xray confirms diagnosis Would show a High patella (Patellar tendon rupture) (Image) or Low patella (Quadriceps tendon rupture)

Question 27

What is the treatment of extensor tendon mechanism of the knee rupture?

Answer 27

treatment of complete and substantial partial tears is surgical with tendon to tendon repair or reattachment of the tendon to the patella.

Question 28

What is patellofemoral pain syndrome and what is it also known as? Who does it typically affect?

Answer 28

Patellofemoral pain syndrome (aka anterior knee pain, aka patellofemroal dysfunction) is a term that describes pain that occurs in front of your knee behind the patella It typically occurs in young, active females (especially runners)

Question 29

The pull of the quadriceps muscle tends to pull the patella in a slight lateral direction. In some people, excessive lateral force produces anterior knee pain and the lateral facet of the patella is compressed against the lateral wall of the distal femoral trochlea Why does the reason mentioned above make patellofemoral dysfunction more likely in females?

Answer 29

Females have wider hips resulting in a more lateral pull of the quadriceps, especially during adolescence

Question 30

What is thought to be the potential factors predisposing to patellofemoral pain syndrome?

Answer 30

Possibly associated with \* Muscle imbalance \* Lower limb alignment - genu valgum, femoral neck anteversion \* Maybe ligamentous laxity

Question 31

What do patients complain of in patellofemoral dysfunction?

Answer 31

Patients complain of anterior knee pain, worse when going downhill (quadriceps have to be in eccentric contraction to slow knee flexion) Grinding or clicking sensation at the front of the knee and stiffness after prolonged sitting (pseudolocing) may also occur

Question 32

What is the intiial treatment of patellofemoral dysfucntion?

Answer 32

Vast majority (approx 90%) improve with physiotherapy aimed at rebalancing the qudriceps muscle (specifically strengthengin the vastus medialis) Taping may help alleviate symptoms

Question 33

What is the last resort treatment for patellofemoral dysfunction?

Answer 33

Surgery is a last resort with about a 70% success rate and may involve either releasing a tight lateral retinaculum or if there is a relatively lateralized tibial tubercle, a tibial tubercle transfer to aid patellar tracking.

Question 34

What is patellar instability and which age group is it most common? What causes it? What ligament can it cause to tear?

Answer 34

Patellar instability is dislocation and subluxation of the patella - it is most common in adolescents It is often related to trauma - direct blow or sudden twist of the knee This can cause a tear in the medial patellofemoral ligament (can cause an osteochondrol fracture)

Question 35

What are predisposing risk factors to patellar instability?

Answer 35

\* Ligamentous laxity \* Female gender \* Shallow trochlear groove \* Genu valgum \* Femoral neck anteversion \* High riding patella (patella alata)

Question 36

What direction does the patella dislocate in? How is it relocated? What type of effusion usually occurs?

Answer 36

The patella virtually always dislocates laterally and may spontaneously reduce wen the knee is straightened or rarely may require to be manually manipulated back into position. A lipo-haemarthrosis occurs in patellar dislocation

Question 37

The risk of recurrent dislocation after first time dislocation is around 10%. What is the treatment of patello femoral instability? - both for first time and recurrent dislocations

Answer 37

Physiotherapy to strengthen quadriceps is usually treatment If recurrent dislocations are frequent, tibial tubercle transfer or medial patellofemoral ligament (MPFL) reconstruction with tendon autograft may help