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JukkaRistiniemi

Knee Injuries

Essentials

  • A knee injury should be diagnosed and treated quickly (in order to reduce the time of disability and the emergence of late complications).
  • Dislocation of the knee joint (possible vascular damage; does not apply to the dislocation of the patella) and all open injuries warrant immediate referral.
  • If several ligaments are involved and valgus or varus deformity can be produced with the knee extended, the patient needs to be referred quickly, perhaps on the following day.

History

  • An accurate history is important.
  • The patient should be allowed to explain without being hurried
    • what happened (did the trauma involve a blow/twisting)
    • the duration of initial recovery (days/weeks)
    • what were the initial symptoms (swelling, amount and location of pain)
    • what is the current situation (pain, locking, instability).

Typical history of the most common knee injuries

Injury of the meniscus

  • Occurs when rotational force is applied to a flexed knee or, particularly in older patients, as a result of a twisting injury.
  • The initial pain is moderate, principally in the joint space, accompanied by slight swelling followed by locking of the knee, especially when squatting.
  • Occasional sharp pain when twisting the knee
  • Asymptomatic from time to time

Torn anterior cruciate ligament (ACL)

  • Occurs as a result of a violent twisting motion of the knee, of landing from a jump (e.g. snowboarders) or of an abrupt stop of movement (e.g. floorball, football).
  • Almost without exception the patient gives a history of immediate swelling and restricted range of movement. Torn ACL is the aetiology in half of cases of knee haemarthrosis.
  • The associated pain is non-specific and is either difficult to locate or is felt laterally (bone contusion).
  • Recovery is slow, i.e. 2-6 weeks.
  • Immediately after the injury, the patient will feel instability in the knee (the knee ”gives away”) when trying to quickly change direction when walking.
  • If the injury is old, the patient will give a history of feelings of instability of the knee, followed by pain, with asymptomatic periods in-between.

Dislocation of the patella

  • Usually the patient is able to recall an obvious dislocation of the patella. The patella almost without exception dislocates laterally but the patient may describe the dislocation occurring inwards.
  • The patient often gives a history of severe post-injury swelling.
  • The pain is either difficult to localise or is felt at the medial aspect, next to the patella, or sometimes in front of the lateral condyle of the femur.
  • Bruising at the medial side of the patella
  • See also Dislocation of the Patella.

Torn medial collateral ligament

  • Caused by a valgus force/twisting injury
  • The injury usually involves the upper attachment site.
  • Severe local pain at the site of the medial condyle of the femur (epicondyle), and any movement into valgus causes pain.
  • The initial, pain-induced restriction to the range of movement may last for several days or even weeks.
  • There is no significant joint swelling, but local swelling and bruising will be evident on the medial aspect of the knee.
  • Tenderness on palpation may persist for several months.

Physical examination

Clinical investigations

  • Compare with the unaffected knee.
  • Visual inspection: swelling, haematoma, location of the patella
  • Active and passive range of movement. Is the patient able to actively extend the knee (injury to the extensor tendon)?
  • When lying down is the patient able to lift the leg up straight?
  • Is weight bearing possible? In soft tissue damage weight bearing is usually possible, but not in fractures.
  • Examination of knee instability, see table T1.

Examination of knee instability

InstabilityTestTissues tested
Medial (valgus)Attempt to produce valgus deformity with the knee flexed to 30ºMedial collateral ligament, ACL
Attempt to produce valgus deformity with the knee extendedMedial collateral ligament, ACL, PCL (posterior cruciate ligament), popliteus tendon, posterior capsule, avulsion fracture of the fibular head
Lateral (varus)Attempt to produce varus deformity with the knee flexed to 30ºLateral collateral ligament, ACL
Attempt to produce varus deformity with the knee extendedLateral collateral ligament, ACL, PCL, posterior capsule
PosteriorThe posterior drawer testPCL
AnteriorThe Lachman test (anterior)ACL
AnteromedialThe anterior drawer test with external rotationMedial collateral ligament, medial posterior capsule, ACL
HyperextensionAttempt to produce hyperextensionACL, PCL, posterior capsule
AnterolateralPivot test (with internal rotation), lateral rotatory stress (see the text)ACL, lateral capsule, iliotibial band, lateral collateral ligament
PosterolateralReverse pivot test (with external rotation; see the text)Posterolateral capsule tissues, popliteus tendon, PCL

Evaluation of swelling

  • The knee joint cavity extends 4-6 cm above the patella. In acute injuries, swelling is evident above the patella.
  • Swelling may be evaluated by placing the fingers of one hand on both sides of the patella and the other hand above the patella. Fluid movement may be felt when squeezing the hands alternatively (compare with a fluid-filled balloon).
  • Knee arthrocentesis is not a primary examination in a knee injury. In the case of painful, massive swelling, it may be performed laterally at the level of patellofemoral joint.

Vascular status

  • Multiligament injuries may also result from a reduced knee dislocation: check vascular status (distal pulses).

Lachman test

  • Superior to the drawer test in determining anterior cruciate integrity
  • The examiner places one hand on the patient's thigh just above the patella and the other one on the tibia at the site of the tibial tuberosity. With the knee flexed at 20°-30° an attempt is made to lift the tibia forward in relation to the femur. The test is most successful if the examiner's knee or a hard pillow is placed under the patient's thigh. The test is positive and suggestive of a torn ACL if abnormal anterior tibial displacement (compare with the other side) with a spongy endpoint is detected 2.

Drawer test

  • Both the anterior and posterior drawer test should be carried out with the knee flexed in 80°-90°. Any displacement is compared with the unaffected knee (ACL and PCL injuries) 3.
  • If the tibia pulls forward more than is normal with no definite endpoint the test is positive and suggestive of an ACL tear. If the PCL is torn, the tibia will sag behind (posterior sag sign).

Lateral pivot shift test

  • Superior to both the Lachmann test and the drawer test in determining anterior cruciate integrity, but its performance requires experience.
  • Can only be carried out if extension of the knee is possible.
  • A torn ACL will cause rotational laxity. The lateral condyle of the tibia will subluxate anterior to the femoral condyle when internal rotation is applied to the tibia with the knee extended 4. Knee flexion will provide reduction with accompanying obvious jerk.

Collateral ligaments

  • The test is carried out both with the knee extended and in about 20° flexion (adduction-abduction test), keeping other structures relaxed 5. Valgus or varus instability in an extended knee is suggestive of extensive injury involving a collateral ligament, joint capsule and cruciate ligament.

Patella and extension of the knee

  • The extension power (fracture of the patella or tendon detachment) and lateral stability of the patella must be tested. After subluxation, an apprehension sign may be elicited by pushing the patella laterally. This will provoke an unpleasant feeling or a sensation of subluxation and the patient will contract the ipsilateral quadriceps muscle.
  • Testing of the extensors of the knee, in supine position with the knee extended: if the patient is unable to raise his/her knee off the surface, a tear in the tendinous part of the quadriceps femoris muscle should be suspected and the patient should be immediately sent for surgical assessment.

Examining a torn meniscus

  • The most reliable examination will include the combination of the McMurray test, Apley test and palpation of the joint space.
  • McMurray test:
    • Medial meniscus: The patient in supine position. Place a finger at the medial joint space and grasp the foot with the other hand. Flex the knee while applying a varus force to it. Keeping the leg externally rotated extend the knee. Repeat the manoeuvre with internal rotation. If the patient feels pain in the joint or a click is felt in the joint space, the test suggests a meniscus tear.
    • Lateral meniscus: Palpate the lateral joint space and apply a valgus force to the knee. Carry out the manoeuvre both with external and internal rotation.
    • The click can often be provoked, when the leg is rotated in relation to the femur while the knee is in extreme flexion position: a click during outward rotation suggests a tear of the medial meniscus and a click during inward rotation suggests a tear of the lateral meniscus. Locating the click is often difficult, but a clear click strongly suggests a tear.
  • Apley test:
    • The patient in prone position with the thigh pressed against the surface and the knee in 90° flexion. Rotate the leg whilst applying traction to the leg and foot (pain indicates a ligament injury). Then compress the leg onto the knee joint while being rotated (pain and clicking in the joint space indicate meniscal injury).

Other investigations

  • Plain x-rays should be considered after the injury if at least one of the following is true:
    1. the patient is aged 55 years or older
    2. there is tenderness at the head of the fibula
    3. there is isolated tenderness of the patella
    4. the patient cannot flex the knee to over 90°
    5. the patient cannot weight bear for 4 steps immediately after the injury or in the emergency department.
  • An ultrasound examination is only indicated if an injury to the extensor tendon is suspected. The most powerful diagnostic tool comprises magnetic resonance imaging.
  • If unclear symptoms are suspected to be caused by meniscal injury, MRI study is the first-line examination in differential diagnostics.
  • In acute dislocation of the patella, an early MRI within 1-3 weeks to investigate joint strucure and associated injuries.
  • Only 12% of ACL injuries occur without associated injuries: early MRI within 1-2 weeks to investigate possible associated injuries.

Treatment

  • Dislocation of the knee joint (possible vascular damage; does not apply to the dislocation of the patella) and all open injuries warrant immediate referral. If several ligaments are involved and valgus or varus deformity can be produced with the knee extended, the patient needs to be referred quickly, perhaps on the following day.

Dislocation of the patella

  • See Dislocation of the Patella
  • Treatment is conservative.
  • Reduction involves extending the knee and applying lateral pressure.
  • Patellar support may be worn initially for 1-3 weeks to keep the patella in situ.
  • Thigh muscle exercises must be taught to the patient. The aim is to return the full range of movement.
  • Indications for immediate surgery: osteochondral fracture, massive swelling, patella not staying in situ.
  • Surgery is also considered in cases of recurrent dislocation.

Torn ACL

  • Initial symptoms include pain and restricted range of movement.
  • Thigh muscle exercises must be taught to the patient; extension of the knee, in particular, should be restored as soon as possible.
  • Not all ACL tears require surgical repair. There is no definite evidence in favour of surgical management Interventions for Anterior Cruciate Ligament Ruptures in Adults, but modern surgical procedures provide good stability and are associated with very few complications.
  • A surgical opinion is often useful when deciding on the treatment management.
  • A patient with sports activities that are challenging for the knee and who on early clinical examination shows tibial displacement of more than 5 mm on the Lachmann test and a positive finding on the pivot shift test will benefit from reconstruction surgery.
  • The ideal time for surgical intervention is approximately 4 weeks after the injury. Surgery may only be considered if the thigh muscle functions well and the knee can be fully extended.
  • The surgery consist of the removal of the torn ACL, and a replacement ligament is made out of the patients own tendons (the pes anserinus tendons or the mid-third of the patellar ligament).

Torn PCL

  • Surgery is only rarely considered in an isolated injury.
  • A torn PCL may heal with conservative management. Subluxation of the lower leg may be prevented by wearing an extension brace.
  • Surgical opinion is usually warranted since significant instability may result if the injury involves several ligaments (urgent referral).

Injury to the medial collateral ligament

  • Problems include pain and restricted range of movement.
  • Full range of movement is allowed and thigh muscle exercises must be taught to the patient.
  • Extending the knee is particularly painful and hence there is a risk of extension deficit.
  • Mobilisation must be checked.
  • Significant instability may result if the injury involves several ligaments (urgent referral).

Combined rupture of ACL and the medial collateral ligament

  • Rupture of ACL and the medial collateral ligament with no valgus instability in an extended knee: initially the collateral ligament tear is treated conservatively by free mobilization, followed by a reconstruction of the ACL preferably within 2-6 weeks.

Meniscus injury

  • Torn meniscus is a common injury even in an asymptomatic patient.
  • An evaluation should always be made as to how much of the patient's problems are attributable to general degeneration of the knee and how much to a torn meniscus.
  • Keyhole surgery may be indicated in a young person if the tear causes mechanical locking, which will manifest as a knee lock.
  • Timing of the operation
    • Repair by surgery is attempted within 1-2 weeks if a young person has a torn meniscus caused by an injury mechanism and a clear disabling mechanical knee-locking symptom.
    • In an osteoarthritic knee, the knee-locking symptom will subside with time, and a longer follow-up is thus reasonable.

Fractures

  • All condylar fractures of the femur or tibia must be assessed by a surgeon.
  • Dislocation may be difficult to see from plain x-rays.
  • Undisplaced fractures of the patella may be treated conservatively with immediate mobilisation or with short term plaster application (up to 1-3 weeks). If dislocation is > 2 mm, referral to a surgeon is indicated.

Knee supports

  • An injured knee must not be immobilised without a diagnosis.
  • Elastic bandages, neoprene supports etc. are not beneficial in the treatment of knee injuries. It may, however, be of significance for the patient-physician relationship that an elastic bandage is applied to relieve pain (not too tight, removed for the night).
  • Patellar support may be of benefit in an acute dislocation of the patella.
  • A hinged knee orthosis is used in the treatment of collateral ligament injuries. Full range of movement is allowed.

Follow-up care of a knee injury

  • Soft tissue damage of the knee will affect the functioning of the thigh muscle leading to restricted movement.
  • Thigh muscle exercises must be taught to the patient . The aim should be to restore the normal range of movement as soon as possible.
  • Return to physical activity should be allowed when no significant hydrops remains in the knee joint.
  • Full range of movement should be restored as soon as possible after cruciate ligament surgery, and return to sporting activities is allowed 4-8 months after the injury, depending on the type of sport.

    References

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    • Boden SD, Davis DO, Dina TS, Stoller DW, Brown SD, Vailas JC, Labropoulos PA. A prospective and blinded investigation of magnetic resonance imaging of the knee. Abnormal findings in asymptomatic subjects. Clin Orthop Relat Res 1992 Sep;(282):177-85. [PubMed]
    • Frobell RB, Roos EM, Roos HP et al. A randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med 2010;363(4):331-42. [PubMed]. Erratum in: N Engl J Med. 2010 Aug 26;363(9):893
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