• Medial collateral ligament (MCL) - prevents lateral movement of the tibia on the femur when valgus (away from the midline) stress is placed on the knee. Runs between the medial epicondyle of the femur and the anteromedial aspect of the tibia. Also has a deep attachment to the medial meniscus.
• Lateral collateral ligament (LCL) - prevents medial movement of the tibia on the femur when varus (towards the midline) stress is placed on the knee. Runs between the lateral epicondyle of the femur and the head of the fibula.
• Anterior cruciate ligament (ACL) - controls rotational movement and prevents forward movement of the tibia in relation to the femur. Runs between attachments on the front (hence anterior cruciate) of the tibial plateau and the posterolateral aspect of the intercondylar notch of the femur.
• Posterior cruciate ligament (PCL) - prevents forward sliding of the femur in relation to the tibial plateau. Runs between attachments on the posterior part (hence posterior cruciate) of the tibial plateau and the medial aspect of the intercondylar notch of the femur.

Medial collateral ligament

The MCL is composed of superficial and deep portions:

• Superficial MCL - anatomically this is the middle layer of the medial compartment. The proximal attachment is the posterior aspect of medial femoral condyle and the distal attachment is to the metaphyseal region of the tibia. Its function is to provide primary restraint to valgus stress at the knee.
• Deep MCL - this is the deep layer of the medial compartment, which in many cases will be separated from the superficial MCL. It inserts directly into the edge of the tibial plateau and meniscus.

Assessment

See also separate article Knee Assessment (History and Examination).

The valgus stress test:¹

• The valgus stress test is performed with the hip abducted and the knee at 30° of flexion.
• This test is performed to measure the amount of joint-line opening of the medial compartment which could indicate an MCL complex injury; also, to look for potential rotation of the tibia on the distal femur.
• The leg is placed over the edge of the table and the examiner places his/her thigh against the patient's thigh to stabilise it.
• The fingers of one hand are placed directly over the joint line to feel for the amount of joint-line opening that occurs when the other hand creates valgus stress by pressure on the anterior aspect of the ankle.
• When proficient, the amount of joint-line opening can be quantified to between 0-5 mm, 5-10 mm, and greater than 1 cm. This would indicate either a mild, moderate, or complete tear of the MCL complex.

The clinical findings may be subtle even with complete injury.

Radiographic assessment:

• X-ray: look for the Pellegrini-Stieda phenomenon - with chronic injury it is common to see calcification at the origin of the MCL.²
• MRI: MCL is best visualised on T2 weighted images. Any concomitant meniscal tear should also be visible.³

Management

Physiotherapy is an integral part of the management of knee injuries in both the conservative and surgical settings.⁴

General points:

• Management aims are to manage pain, minimise knee swelling, maintain range of movement and quadriceps activation, and arrange appropriate referral.
• Rest, ice, compression, elevation (RICE), and non-weight bearing restriction with the use of crutches (often only required for a few days) are recommended. Bracing and non-weight bearing may be sufficient for mild injury.

• Optimum healing of the MCL occurs when the torn ends are in contact. Maturation of the scar occurs from 6 weeks to up to one year. The maturing scar tissue has only about 60% of the strength of the normal MCL.
• The surgical plan depends on whether injury is proximal, mid-substance, or distal. The knee should be held flexed at 30° and held in varus when the ligament is reattached.

Complications

Early operative treatment of combined ACL and MCL injuries can lead to restriction of movement and slow recovery of the quadriceps muscle. Aggressive physiotherapy may be required and nonoperative treatment may be preferred.⁵

Prevention

Prophylactic knee bracing has shown promise in preventing injury to the MCL.⁶

Lateral collateral ligament

This is the primary restraint to varus angulation. LCL also acts to resist internal rotation forces.⁷

Assessment

See also separate Knee Assessment (History and Examination) article.

Varus stress testing:

• The varus stress test is slightly more difficult to perform than the valgus test because the table begins to get in the way of performing the test correctly.
• The patient's thigh is placed slightly more away from the table and one hand is placed with the thumb stabilising the lower extremity and the fingers or thumb placed directly over the lateral joint line.
• In this position, the amount of joint-line opening that occurs can be palpated.
• It is important that this hand also serve to stabilise the extremity such that true amount of instability can be felt.
• The other hand is placed over the patient's foot and is used to apply varus stress with the knee flexed at 30°.
• Increased varus opening is assessed and compared with the normal contralateral knee. Mild (0-5 mm), moderate (5-10 mm), or severe (>10 mm) lateral compartment opening, compared with the normal knee is usually indicative of at least a posterolateral knee injury and potentially an ACL and/or PCL injury.

Management

General points:

• This is mainly surgical although, as with the other injuries, managing pain, minimising knee swelling, maintaining range of movement and quadriceps activation and arranging appropriate referral are also important. Rest, ice, compression, elevation (RICE), and non-weight bearing restriction with the use of crutches are recommended. Hinged bracing may also be helpful.

• Achilles allograft reconstruction may be used with chronic posterolateral injury. The main goal is to create a restraint for external rotation. A return to full weight bearing gait should be gradual over the course of 4 weeks.⁸

Anterior cruciate ligament

ACL tears most often occur in younger patients during football and basketball and, in older patients, occur most often from skiing injuries.⁹ Substantial anterior tibial shear forces that stress the ACL are produced from quadriceps contraction, especially in 0-30° of extension. Typically, the ACL is torn in a noncontact deceleration situation that produces a valgus twisting injury. This usually occurs when the athlete lands on the leg and quickly pivots in the opposite direction.

Mechanisms reported as possibly able to disrupt the ACL with minimal injury to other structures are:

• Hyperextension.
• Marked internal rotation of the tibia on the femur.
• Pure deceleration.

Assessment

The anterior drawer test:

• Flex the knee to 90°.
• Hold the position by sitting on the patient's foot.
• Ensure that the hamstring muscles are relaxed.
• With both hands, grasp below the knee and pull the tibia forward.
• Compare the degree of movement with the other side.
• Excessive movement may indicate ACL disruption.

Lachman's test:

• Flex the knee to 15-20°.
• Hold the lower thigh in one hand and the upper tibia in the other.
• Push the thigh in one direction and pull the tibia in the other.
• Reverse the direction, pushing the tibia and pulling the thigh, and look for increased movement or laxity between the tibia and the femur.

Pivot shift test:

• Hold the patient's heel with one hand.
• Internally rotate the foot and the tibia and, at the same time, apply an abduction (valgus) force at the knee.
• Flex the knee from 0° to 30° whilst applying this force and still holding the foot and tibia in internal rotation.
• Try to detect any palpable or visible reduction between the femur and the tibia.

• MRI of the knee is most commonly indicated in patients with suspected injuries of the menisci and cruciate ligaments.¹⁰ Plain radiographs have little value unless there has been an injury due to direct impact. In teaching centres where dedicated musculoskeletal radiologists report on images, diagnostic accuracy of 90% can be achieved for damage to the medial meniscus and ACL, slightly less for the lateral meniscus and slightly more for the PCL.

Management

General points:

• Most tears are managed surgically; however, some if, for example, they are not highly active or athletic or are minimally symptomatic, may choose conservative management. Management aims are to manage pain, minimise knee swelling, maintain range of movement and quadriceps activation and arrange appropriate referral.
• In conservative management, after initial control of pain and effusion, hamstring and quadriceps activation/disinhibition and protected weight bearing in a hinged brace should be recommended. As swelling and pain slowly resolve, range of movement should return to normal, or nearly normal, parameters. Exercises should be advised that take place in an anterior/posterior plane, e.g. stationary cycling.¹¹

• Each patient should be assessed individually with regards to the type and frequency of physical activity and the degree of laxity at presentation. In some circumstances primary reconstruction may be considered once the knee has settled and there is no swelling and a full range of movement has been restored.
• For complete rupture, where no local healing response is detectable at the injury site, a graft must be used to replace the ACL. There are 4 options used. The first 3 types are autografts using the central one third of the patellar ligament or the quadriceps tendon. The fourth type of graft is a cadaveric allograft.
• There is a lack of robust data for timing of intervention and material used for the graft.¹²

Complications

Early surgery may be associated with arthrofibrosis.

Posterior cruciate ligament

The PCL provides 95% of the total restraining force to straight posterior displacement of the tibia relative to the femur.¹³ Its secondary action includes resistance to varus, valgus, and external rotation. Hyperflexion is the most common mechanism for an isolated PCL injury and this type of injury does well with conservative treatment.

Assessment

See also separate Knee Assessment (History and Examination) record.

Associated injuries include ACL and collateral ligament injury (knee dislocation) and tibial plateau rim fractures, and any assessment should consider this.

The pain, degree of swelling and disability associated with ACL and MCL injuries is often missing from the patient's history. Many are able to walk with normal gait immediately after the injury. The soft endpoint of the posterior drawer test is firm by 2-3 weeks after injury.

Posterior drawer test:

• Perform the same examination as the anterior drawer test but pushing backwards in relation to the tibia instead of pulling forwards.
• Compare the degree of movement with the other side.

Posterior sag test:

• Flex both knees to 90°.
• Look at the position of the tibia in relation to the femur.
• If there is rupture of the PCL, the position will be relatively posterior.

• MRI assessment for extent and position of damage.

Management

General points:

• Management aims are to manage pain, minimise knee swelling, maintain range of movement and quadriceps activation and arrange appropriate referral.
• Apply the rest, ice, compression, and elevation (RICE) method several times a day, in addition to any other modalities incorporated by the physiotherapist to control pain and swelling, e.g. electrical stimulation, cold whirlpool.
• Patients with minimal injuries can bear weight as tolerated immediately, although some may require axillary crutches initially.
• Axillary crutches and a long leg brace are recommended for more severe injury.

• Indications for operative treatment include acute injuries, an active young patient and severity of injury. Several different techniques may be used to reconstruct the PCL, so the treatment protocol is determined by the individual physician and the type of graft used in surgery.

Prognosis

Conservatively managed patients do well and, in one study (with a mean follow-up of 6.2 years), 80% of patients were satisfied with their knees and 84% had returned to their previous sport (68% at the same level of performance, 16% at a decreased level of performance).¹⁴

If left untreated PCL ruptures may lead to chronic patellofemoral as well as medial compartment arthrosis.

Document references

1. Sports Medicine Institute. University of Minnesota. Valgus Stress test (pictures and video).
2. Medial collateral ligament, Wheeless' textbook of orthopaedics
3. Jacobson KE, Chi FS; Evaluation and treatment of medial collateral ligament and medial-sided injuries Sports Med Arthrosc. 2006 Jun;14(2):58-66. [abstract]
4. Scotney B; Sports knee injuries - assessment and management. Aust Fam Physician. 2010 Jan-Feb;39(1-2):30-4. [abstract]
5. Halinen J, Lindahl J, Hirvensalo E; Range of motion and quadriceps muscle power after early surgical treatment of J Bone Joint Surg Am. 2009 Jun;91(6):1305-12. [abstract]
6. Miyamoto RG, Bosco JA, Sherman OH; Treatment of medial collateral ligament injuries. J Am Acad Orthop Surg. 2009 Mar;17(3):152-61. [abstract]
7. Lateral collateral ligament, Wheeless' textbook of orthopaedics
8. Ho SS, Erikson BC; Lateral Collateral Knee Ligament Injury. eMedicine. Feb 2010.
9. Wheeless' textbook of orthopaedics; Anterior cruciate ligament.
10. McNally EG; Magnetic resonance imaging of the knee. BMJ. 2002 Jul 20;325(7356):115-6.
11. Gammons M, Schwartz E; Anterior Cruciate Ligament Injury. eMedicine. May 2010.
12. Biau DJ, Tournoux C, Katsahian S, et al; Bone-patellar tendon-bone autografts versus hamstring autografts for BMJ. 2006 Apr 29;332(7548):995-1001. Epub 2006 Apr 7. [abstract]
13. Posterior cruciate ligament, Wheeless' textbook of orthopaedics
14. Peterson CS, Agesen T; Posterior Cruciate Ligament Injury. eMedicine. Jan 2010.

Internet and further reading

• DeBerardino TM, Gundel JC; Medial Collateral Knee Ligament Injury. eMedicine. Jan 2010.
• Post-operative knee care. An expert explains how to get your knee back to its best following surgery. Short video from NHS Choices. (April 2008)

Acknowledgements