Which three components make up the knee joint?
- The medial compartment of the tibiofemoral joint
- The lateral compartment of the tibiofemoral joint
- The patellofemoral joint
What is contained within the tibiofemoral joint and what is their function?
Act as shock absorbers and act to distribute load evenly
What are the four main ligaments of the knee?
- Anterior cruciate ligament
- Posterior cruciate ligament
- Medial collateral ligament
- Lateral collateral ligament
What is the role of the ACL?
Prevents abnormal internal rotation of the tibia
What is the role of the PCL?
Prevents hyperextension and anterior translation of the femur
What is the role of the MCL?
Resists valgus force
What is the role of the LCL?
Resists varus force and abnormal external rotation of the tibia
Early OA of the knee may be predisposed by which conditions?
- Previous meniscal tears
- Ligament injuries (esp. ACL deficiencies)
Which treatment can help younger patients with isolated medial compartment OA?
Osteotomy of the proximal tibia
(high tibial osteotomy)
When would knee replacement be indicated?
Substantial pain and disability
Failure of conservative management
What is the treatment for younger patients who have isolated OA in either the medial or lateral compartment of the knee joint?
Unicompartmental knee replacement
(total knee replacement can be utilised if this fails)
Meniscal injuries to the knee classically occur with what?
Twisting force on a loaded knee
How does a patient with a meniscal injury present?
- Localised pain to the joint line (medial or lateral)
- Effusion the following day
- Catching or locking sensation may be present
- Feeling of knee giving way
- Pain on tibial rotation (Steinmann's test)
Which type of meniscal injury (medial or lateral) is more common?
Medial meniscal injury
(it is more fixed and less mobile than its lateral counterpart)
What causes true knee locking?
A significantly torn meniscus flipping over and becoming stuck in the joint line
Knee locking is a clinical sign associated with which knee pathology?
How is knee "locking" with other knee pathologies such as OA different from that of a meniscal tear?
- There is only temporary difficulty in straightening the leg
- It can spontaneously resolve
- The patient may describe a specific manouvre they use to relieve the locking
This is known as pseudo-locking as it is not true locking
What causes ACL ruptures?
High rotational force e.g. turning the body laterally on a planted foot
What is usually felt during an ACL rupture which is characteristic?
A pop sound or feeling
How does an ACL rupture present?
- Haemarthrosis and swelling within an hour
- Deep knee pain
- Rotatory instability
- Excessive anterior translation of tibia on anterior drawer test
Valgus stress injuries usually tear what?
(high forces can also damage the ACL)
Which type of fracture can occur with valgus stress injuries?
Lateral tibial plateau fracture
How is the PCL most commonly ruptured?
- Direct blow to the anterior tibia whent he knee is flexed
A varus stress injury may rupture what?
(potentially also the PCL)
In younger patients, what usually causes a meniscal tear?
High impact sports
Acute meniscal tears are often related to which other injury?
Acute ACL rupture
Large longitudinal tears in the meniscus may lead to what?
Large bucket handle tears with subsequent knee locking due to the meniscal fragment flipping into the intercondylar notch
Degenerate meniscal tears can occur ______________ or with a seemingly ____________ injury
Which type of meniscal tears tend to have complex patterns?
(horizontal, longitudinal and radial components are common)
Degenerate meniscal tears are probably the first stage in the development of which condition?
Steinmann's test will be _________ for degenerate meniscal tears
Why should degenerate meniscla tears not be treated with arthroscopy?
Symptoms from such tears do not improve with resection
Why does the meniscus have limited healing potential and what causes healing potential to decline?
It only has an arterial blood supply to the outer 1/3rd
Age and increased time from injury reduce the healing capacity
Which types of meniscal tears should be considered for repair?
Fresh longitudinal tears involving the outer 1/3rd of the meniscus in a younger patient
If a meniscal repair fails, what is required?
What can aid the symptoms of a degenerate meniscal tear in the early period after injury?
In acute meniscal tears which do not settle after 3 months, what is the treatment?
Arthroscopic partial menisectomy
Why are knees with degenerate changes on X-ray unlikely to benefit from arthroscopic menisectomy?
Removal of meniscal tissue is likely to increase stress on already worn and damged knee joint surfaces
What is the pricipal complaint of ACL deficiency?
Rotatory instability with giving way on turning
What is the rule of 1/3rds regarding outcomes for ACL injury?
- 1/3rd compensate well and do what they like
- 1/3rd manage by avoiding specific movements
- 1/3rd do poorly with their knee giving way with normal movements
What are the treatment options for ACL injury?
- Physio - strengthenign of quadriceps and hamstrings aids compensation
- Patients who cope poorly in day to day activities or athletes may require ACL reconstruction
What does ACL reconstruction involve?
A tendon graft (patellar or semitendinosis and gracilis autograft) being passed through tibial and feoral tunnels at the usual location of the ACL in the knee and attachment to the bone
(it may take up to a year to recover fully)
Which is more common, PCL rupture or ACL rupture?
ACL rupture is much more common
What is the treatment for an isolated PCL rupture?
Only those with severe laxity and recurrent instability with frequent hyperextension or feeling unstable when descending stairs are considered for reconstructive surgery
What is used for PCL reconstruction surgery?
Cadaveric achilles tendon allograft
In terms of recovery, what is expected in the majority of MCL tears?
Healing with little or no instability will occur
How are acute MCL tears treated?
Hinged knee brace
What are the options for chronic MCL instability?
- MCL tightening
- Reconstruction with a tendon graft
What is the usual treatment of LCL tears?
Surgical with early repair
Late reconstruction with a tendon graft
With an LCL tear, patient will usually have what type of marked instability?
On rotational movement
(excessive external rotation of the tibia, or varus stress)
What type of movement gives rise to an LCL rupture?
Hyperextension with varus impact
Due to the excessive stretch during a LCL tear, which nerve is commonly affcted or damaged?
(common fibular nerve)
LCL ruptures are associated with multiple ligament knee injuries. Which artery is at risk during such injuries?
Why are regular checks on the circulation in the foot essential for patients with complete knee dislocations?
Intimal tears can occur in vessels which can later thrombose causing thrombosis
If thrombosis occurs in the lower limb subsequent to a complete knee dislocation, what risk does reperfusion pose?
(fasciotomy may be required)
Acute injuries with large osteochondral fragments with large aspects of bone are fixed in what way?
Fixed with pins
Acute injuries with small osteochondral fragments, or fragments in a non-weight bearing area, with small aspects of bone are fixed in what way?
Describe the process of microfracture and why it is utilised
If defects have bare bone at their base microfracture can be used
Involves drilling small holes into the bone base to induce bleeding
This process causes fibrocartilage formation from stem cells which differentiate into chondroblasts
Under which circumstance may a patellar or quadriceps tendon rupture?
Rapid contractile force
(heavy lifing, fall, spontaneously)
What are some predisposing factors for an extensor mechanism rupture?
- Steroid use chronically (commonyl body-builders)
- Chronic renal failure
- Use of quinolone antibiotics (e.g. ciprofloxacin)
Why should steroid injections be avoided in the treatment of tendonitis in the muscles of the extensor mechanism?
High risk of tendon rupture
What is the purpose of the straight leg raise test?
Determines if the extensor mechanism is intact
On X-ray what do the following suggest
a) High-lying patella
b) Low-lying patella
a) Patellar tendon rupture
b) Quadriceps tendon rupture
What is the treatment for complete or substantial partial tears of extensor mechanism ruptures?
Surgical tendon to tendon repair
Surgical reattachment of the tendon to the patella
The pull of the quadriceps muscles tend to pull the patella in a slight _________ direction
Patellofemoral dysfunction is commoner in which sex?
(wider hips and more lateral pull of patella)
Predisosing factors to patellofemoral dysfunction include?
- Female gender
- Joint hypermobility
- Genu valgum
- Femoral neck anteversion
Patients with patellofemoral dysfunction tend to complain of what?
- Anterior knee pain (worse downhill)
- Grinding or clicking at the front of the knee
- Pseudolocking (after prolonged inactivity)
What are the treatment options for patellofemoral dysfunction?
- Physio - especially strengthening the vastus medialis
- Taping - to help alleviate symptoms
- Surgery (a last resort)
The patella always dislocates __________
When the patella dislocates, the ________ ________________ __________ tears and _____________ ____________ may occur
When the patella dislocates, the medial patellar ligament tears and osteochondral fracture may occur
(can be seen on X-ray as small opacification)
In a patellar dislocation, what may be seen on X-ray?
- Small opacification (osteochondral fracture due to medial patellar facet striking the lateral femoral condyle)
Predisposing factors patellar dislocation include?
- Ligamentous laxity
- Female gender
- Shallow trochlear groove
- Genu valgum
- Femoral neck anteversion
- Patella alta (high riding patella)
What are the treatment options for patellar instability?