LIGAMENTOUS KNEE INJURIES Introduction The 4 most important ligamentous injuries of the knee joint involve the: ●
Lateral collateral ligament.
●
Medial collateral ligament
●
Anterior cruciate ligament
●
Posterior cruciate ligament.
Anatomy
Posterior aspect of the left knee joint, showing interior ligaments, (Gray’s Anatomy 1918)
Anterior aspect right knee joint, showing interior ligaments, (Gray’s Anatomy 1918)
LATERAL COLLATERAL LIGAMENT Introduction ●
Lateral collateral ligament ruptures are uncommon when compared to those of the medial collateral ligament.
●
Complete tears are often associated with more extensive associated injury to the cruciate ligaments.
●
The usual mechanism will be a forceful varus injury applied to the medial aspect of the knee.
Mechanism The lateral collateral ligament of the knee is damaged by a forceful varus injury to medial aspect of the knee.
The ligament actually forms part of a greater tendon-ligamentous structure (dotted line) that helps stabilize the lateral knee. This involves, the lateral collateral ligament (1), the biceps femoris tendon (2), and the fascia lata (3). The whole complex attaches to the tibia, lateral patella and head of the fibula. 1 Consequently these other structures may be damaged in association with injury to the lateral collateral ligament. A very significant varus force may also involve the cruciates (5) and the peroneal nerve (6) Clinical Features 1.
Pain and tenderness are usually maximal over the points of bony attachment, at the lateral femoral condyle and/ or the head of the fibula.
2.
Peroneal nerve: ●
3.
Function should be tested by checking for weakness of dorsi-flexion of the foot and great toe and/or sensory loss at the dorso-lateral aspect of the foot.
The lateral collateral ligament: To test the integrity of the lateral collateral ligament, a varus force is applied to the knee joint in 30 degree flexion and again in full extension. When assessing for instability it is often useful to compare with the opposite uninjured joint. In general terms 3 degrees of injury can be described: Grade I:
Pain but the joint is stable, (a sprain of the ligament).
Grade II:
Pain with some opening (< 1 cm) of the joint line, (a partial tear) with a perceived end point.
Grade III:
Significant opening of the joint line, (a complete tear) with no firm end point. Paradoxically pain may be not as severe in lesser degrees of injury as the rupture is complete.
Varus Stress Test: ●
The varus stress test is done at 30 degrees flexion of the knee and at full extension of the knee.
●
There is normally a little medio-lateral movement of the knee at 30 degrees flexion, so comparison with the other side is useful. May pick up a grade II or III injury.
●
Sideways movement in full extension however is always abnormal and indicates severe injury with torn ligaments. This will pick up a grade III injury. Extensive movement suggests that the cruciate ligaments are also involved.
Varus Stress Test: apply a medial force to the distal leg (1) with a lateral force to medial joint line (2) Investigations Plain radiography: Will not directly be able to diagnose a lateral collateral ligament injury, but should be done to: ●
Rule out other bony injury
●
To gain indirect evidence of damage to the ligament by detection of the presence of avulsion fragments.
Avulsion fragments associated with the lateral collateral ligament may be seen: ●
At the upper lateral margin of the lateral tibial condyle where the ligament attaches. This is known as Segond’s fracture, (first described by Paul Segond in 1879), and is an important sign to recognize. The significance of the Segond fracture is that despite the seemingly small bony injury, there is a very high prevalence of internal derangement to both the anterior cruciate ligament and the menisci. Follow-up MRI should be done to look for these injuries.
Segond fracture, left knee, (the small bony fragment just lateral to the proximal lateral tibial plateau). ●
At the tip of the head of the fibula. Larger displaced fragments at this point may indicate avulsion of the biceps femoris muscle.
MRI: This may be considered in cases of: ●
Clinical uncertainty.
●
When more extensive injury is suspected, (especially in the presence of a Segond fracture).
●
Failure of resolution of symptoms with conservative management.
Arthroscopy: ●
This may be considered in cases when more extensive injury is suspected.
Management In general terms 1.
2.
3.
Grade I sprains: ●
Conservative treatment
●
Initially with RICE, (rest, ice compression and elevation)
●
Then tubigrip/ crutches / physiotherapy referral as indicated.
Grade II injuries: ●
Initially with RICE, (rest, ice compression and elevation)
●
Zimmer splint/ crutches/ physiotherapy.
●
The aggressiveness of treatment (conservative versus surgical) will depend in part on the requirements of the individual (elite sports person for example).
●
Early orthopedic review with referral to Sports and Soft tissue injury clinic.
Grade III injuries: ●
These are serious injuries with significant joint instability. An apparent grade III injury to the lateral collateral ligament may also in fact be associated with more extensive injury to the cruciate ligaments.
●
Suspected cases should be referred to the orthopaedic unit for assessment for operative repair.
MEDIAL COLLATERAL LIGAMENT Introduction ●
Medial collateral ligament injuries are much more common compared to lateral collateral ligament injuries.
●
Complete tears are often associated with more extensive associated injury to the cruciate ligaments.
●
The usual mechanism will be a forceful valgus injury applied to the lateral aspect of the knee.
Mechanism ●
The medial collateral ligament of the knee is damaged by a forceful valgus injury to the lateral aspect of the knee.
Clinical Features 1.
Pain and tenderness are usually maximal over the points of bony attachment, at the medial aspect of the femoral condyle and the medial aspect of the tibial condyle.
2.
The medial collateral ligament: To test the integrity of the medial collateral ligament, a valgus force is applied to the knee joint in 30 degree flexion and again in full extension. When assessing for instability it is often useful to compare with the opposite uninjured joint. In general terms 3 degrees of injury can be described: Grade I:
Pain but the joint is stable, (a sprain of the ligament).
Grade II:
Pain with some opening (< 1 cm) of the joint line, (a partial tear) with a perceived end point.
Grade III:
Significant opening of the joint line, (a complete tear) with no firm end point. Paradoxically pain may be not as severe in lesser degrees of injury as the rupture is complete.
Valgus Stress Test: ●
The valgus stress test is done at 30 degrees flexion of the knee and at full extension of the knee.
●
There is normally a little medio-lateral movement of the knee at 30 degrees flexion, so comparison with the other side is useful. May pick up a grade II or III injury.
●
Sideways movement in full extension however is always abnormal and indicates severe injury with torn ligaments. This will pick up a grade III injury. Extensive movement suggests that the cruciate ligaments are also involved.
Valgus stress test: apply a lateral force to the distal leg and a medial force to the lateral joint line. Investigations Plain radiography: Will not directly be able to diagnose a lateral collateral ligament injury, but should be done to: ●
Rule out other bony injury
●
To gain indirect evidence of damage to the ligament by detection of the presence of avulsion fragments.
Avulsion fragments associated with the medial collateral ligament may be seen: ●
At the medial aspect of the medial femoral condyle.
●
At the medial aspect of the medial tibial condyle This has been termed a “Reverse Segond” fracture. 3
They have a high association with disruption of the posterior cruciate ligament and peripheral medial meniscal tears.
White arrow showing a Reverse Segond fracture at the medial proximal tibial plateau of the right knee. The black arrow shows another avulsion fragment of the medial tibial eminence suggestive of a posterior cruciate ligament avulsion. MRI: This may be considered in cases of: ●
Clinical uncertainty.
●
When more extensive injury is suspected, (especially with Reverse Segond fracture).
●
Failure of resolution of symptoms with conservative management.
Arthroscopy: ●
This may be considered in cases when more extensive injury is suspected.
Management In general terms 1.
Grade I sprains: ●
Conservative treatment
2.
3.
●
Initially with RICE, (rest, ice compression and elevation)
●
Then tubigrip/ crutches / physiotherapy referral as indicated.
Grade II injuries: ●
Initially with RICE, (rest, ice compression and elevation)
●
Zimmer splint/ crutches/ physiotherapy.
●
The aggressiveness of treatment (conservative versus surgical) will depend in part on the requirements of the individual (elite sports person for example).
●
Early orthopedic review with referral to Sports and Soft tissue injury clinic.
Grade III injuries: ●
These are serious injuries with significant joint instability. An apparent grade III injury to the lateral collateral ligament may also in fact be associated with more extensive injury to the cruciate ligaments.
●
Suspected cases should be referred to the orthopaedic unit for assessment for operative repair.
ANTERIOR CRUCIATE LIGAMENT Introduction ●
Anterior cruciate ligament (ACL) damage is much more common than posterior cruciate ligament damage.
●
It is most commonly seen in younger patients involved in high impact or contact sports.
●
It is commonly associated with medial collateral ligament damage and medial meniscal damage.
Function of the anterior cruciate ligament: The anterior cruciate ligament: ●
Limits forward movement of the tibia in relation to the femur.
●
Inhibits excessive internal rotation of the knee
●
Limits hyperextension of the knee.
Mechanism ●
A severe hyper-extension force to the knee.
●
Severe internal rotation of the tibia in relation to the femur.
●
Any significant enough valgus or varus force that injures the collateral ligaments of the knee may also damage the cruciate ligaments.
Clinical Features 1.
Pain is usually severe with acute ruptures.
2.
A “snapping” sound may have been experienced.
3.
The knee may suddenly “give-way”.
4.
There may be significant swelling (hemarthrosis) of the knee joint.
5.
Testing anterior cruciate ligament function: The anterior draw test: ●
The knee is flexed to 90 degrees.
●
Secure the foot and attempt to draw the tibia forward in relation to the femur. Make sure that the tibia is not already lying back, indicating a posterior cruciate ligament injury (and thus providing potential for a false positive anterior draw test).
●
It the tibia comes forward, this is a positive anterior draw test.
Lachman’s test: ●
This test is said to be more sensitive than the anterior draw test for the detection of an anterior cruciate ligament injury, although it is a little more difficult to perform correctly.
●
The knee is flexed to 20 degrees only, by the placing of a pillow under the knee.
●
Pull the tibia upwards whilst stabilizing the thigh. Movement upwards (or tibia forwards in relation to the femur) suggests a rupture of the ACL.
Pivot shift test: ●
This test can produce pain and so is often done under anaesthetic.
●
With the knee fully extended, the ankle is grasped and the tibia internally rotated. Then apply a valgus force keeping the tibia internally rotated and flex the knee past 30 degrees. If a “clunk” is detected this means that a degree of subluxation has occurred consequent to an ACL rupture.
Investigations Plain radiography: Will not directly be able to diagnose an anterior cruciate ligament injury, but should be done to: ●
Rule out other bony injury
●
To gain indirect evidence of damage to the ligament by detection of the presence of avulsion fragments.
Avulsion fragments associated with the anterior cruciate ligament may be seen: ●
At the anterior tibial spine.
MRI: ●
This is the best non-invasive investigation to make the diagnosis.
Arthroscopy: ●
This may be done when exact diagnosis is unclear on MRI
●
It has the advantage of allowing therapeutic intervention at the same time as the imaging.
Management 1.
Analgesia: ●
2.
RICE ●
3.
Pain is often severe and narcotics will be required.
Initial first aid management will consist of the soft tissue RICE, treatment, (rest, ice, compress and elevate.)
Note that full assessment of the knee may be impossible acutely due to the degree of patient distress. A high index of suspicion for a significant injury however may be indicated by: ●
Inability to weight bear.
●
The severity of symptoms.
●
The degree of associated haemarthrosis.
●
The mechanism if injury.
Initial radiology will be needed to rule out bony injury or even knee joint dislocation and where significant concern remains the patient should be referred to the orthopaedic unit for possible MRI/ EUA/ arthroscopy. 4.
Surgical repair: Not all patients will show the same degree of long term knee joint instability if left unrepaired. Some may show surprisingly minimal instability whilst will others will show incapacitating symptoms. If left unrepaired all will: ●
Eventually suffer increased secondary degenerative joint disease
●
Be more liable to further injury.
●
Suffer from problems relating to an unstable joint such as giving way with consequent limitation of normal activities to varying extents.
The decision to undergo surgical repair therefore will depend on a number of factors including: ●
The age and co-morbidities of the patient
●
The expectations of the patient
●
The profession of the patient (eg elite or professional athlete).
●
The motivation/ ability of the patient to undergo operation followed by a prolonged period of intensive rehabilitation and physiotherapy.
POSTERIOR CRUCIATE LIGAMENT Introduction ●
Posterior cruciate ligament damage is much less common than anterior cruciate ligament damage. In fact an isolated injury to the posterior cruciate ligament is uncommon.
Function of the posterior cruciate ligament: ●
The posterior cruciate ligament limits excessive posterior movement of the tibia in relation to the femur.
Mechanism ●
Damage to the posterior cruciate ligament may occur with falls in which the tibia strikes an object and is forced backwards. This may also occur in motor vehicle dashboard injuries whereby the knee strikes the dashboard in head on collisions.
●
Any significant enough valgus or varus force that injures the collateral ligaments of the knee may also damage the cruciate ligaments.
Clinical Features 1.
Pain is usually severe with acute ruptures.
2.
A “snapping” sound may have been experienced.
3.
The knee may suddenly “give-way”.
4.
There may be significant swelling (hemarthrosis) of the knee joint.
5.
Testing posterior cruciate ligament function: The posterior draw test: ●
The knee is flexed to 90 degrees.
●
Observe the position of the tibia in relation to the femur. If it is sitting backwards (compared to the good side) it is likely that there is a rupture of the posterior cruciate ligament.
●
Otherwise secure the foot and attempt to push the tibia backward in relation to the femur.
●
It the tibia does show backward movement, this is a positive posterior draw test.
Investigations Plain radiography: Will not directly be able to diagnose an posterior cruciate ligament injury, but should be done to: ●
Rule out other bony injury.
●
To gain indirect evidence of damage to the ligament by detection of the presence of avulsion fragments.
Avulsion fragments associated with the posterior cruciate ligament may be seen: ●
At the posterior tibial spine.
MRI: ●
This is the best non-invasive investigation to make the diagnosis.
Arthroscopy: ●
This may be done when exact diagnosis is unclear on MRI
●
It has the advantage of allowing therapeutic intervention at the same time as the imaging.
Management 1.
Analgesia: ●
Pain is often severe and narcotics will be required.
2.
RICE ●
3.
Initial first aid management will consist of the soft tissue RICE, treatment, (rest, ice, compress and elevate.)
Note that full assessment of the knee may be impossible acutely due to the degree of patient distress. A high index of suspicion for a significant injury may be indicated by: ●
Inability to weight bear
●
The severity of symptoms
●
The degree of associated haemarthrosis.
●
The mechanism if injury
Initial radiology will be needed to rule out bony injury or even knee joint dislocation and where significant concern remains the patient should be referred to the orthopaedic unit for possible MRI/ EUA/ arthroscopy. 4.
Surgical repair: Not all patients will show the same degree of long term knee joint instability if left unrepaired. Some may show surprisingly minimal instability whilst will others will show incapacitating symptoms. If left unrepaired all will: ●
Eventually suffer increased secondary degenerative joint disease.
●
Be more liable to further injury.
●
Suffer from problems relating to an unstable joint such as giving way with consequent limitation of normal activities to varying extents.
The decision to undergo surgical repair therefore will depend on a number of factors including: ●
The age and co-morbidities of the patient
●
The expectations of the patient
●
The profession of the patient (eg elite or professional athlete).
●
The motivation/ ability of the patient to undergo operation followed by a prolonged period of intensive rehabilitation and physiotherapy.
References 1.
McRae R. Practical Fracture Treatment. 3rd ed 1994
2.
Apply’s System of Orthopaedics and Fractures 7th ed 1993.
3.
Escobedo EM et al. The “reverse Segond” fracture: association with a tear of the posterior cruciate ligament and medial meniscus.
Dr J. Hayes Reviewed February 2009.
