An injury to the knee can lead to sprained external ligaments (medial and lateral collateral) or internal ligaments (anterior and posterior cruciate) or meniscal injuries

Symptoms include pain, joint effusion, instability (in the case of severe sprains) and joint locking (in the case of meniscal injuries).

Diagnosis is based on clinical examination and sometimes MRI.

Treatment consists of PRICE therapy (protection, rest, ice, compression and elevation) and, in the case of severe injuries, immobilisation with a plaster cast or surgical repair.

Many structures that help provide stability to the knee are located primarily outside the joint; these include the joint muscles (e.g. the quadriceps muscle and the thigh flexor muscles), their insertion (e.g. the goose foot) and the extracapsular ligaments.

The external collateral ligament is extracapsular; the internal (tibial) collateral ligament has a superficial extracapsular portion and a deep portion that is part of the joint capsule.

Inside the knee, the joint capsule and the highly vascularised anterior and posterior cruciate ligaments help stabilise the joint.

The medial and lateral menisci are intra-articular cartilaginous structures that act primarily as shock absorbers, but provide some stabilisation.

The most commonly injured knee structures are

• Medial collateral ligament
• Anterior cruciate ligament

The mechanism of injury is predictive of the type of injury:

• An inward force (valgus): generally, the medial collateral ligament, followed by the anterior cruciate ligament, then the medial meniscus (this mechanism is the most common and is usually accompanied by some external rotation and flexion, as occurs in football)
• An outward force (varus): often, the lateral collateral ligament, the anterior cruciate ligament, or both (this mechanism is the 2nd most common)
• Anterior or posterior forces and hyperextension: typically, the cruciate ligaments
• Loading and rotation at the time of injury: usually the menisci

Symptomatology

Swelling and muscle spasm occur in the first few hours.

In the case of 2nd degree sprains, the pain is typically moderate or severe.

In the case of 3rd degree sprains, the pain can be moderate, and surprisingly, some patients can walk unaided.

When the injury occurs, some patients hear or feel a pop.

This finding suggests a tear in the anterior cruciate ligament, but is not a reliable indicator.

The location of the soreness and pain depends on the knee injury:

• Medial or lateral ligament sprain: swelling over the damaged ligament
• Medial meniscal injuries: pain in the joint plateau (swelling of the joint line) medially
• Lateral meniscal injuries: pain in the lateral joint plateau
• Medial and lateral meniscal injuries: pain aggravated by extreme flexion or extension and limitation of passive knee movement (lockout)

Injuries to any of the knee ligaments or menisci cause a visible and palpable joint effusion

The ballot test (patellar tap) can be used to check for joint effusion.

It is best when the patient lies supine.

The examiner uses one hand to slide the quadriceps muscles firmly towards the knee and stops several centimetres above the knee joint.

With the other hand, the examiner taps the kneecap.

If the kneecap bounces (ballotte), the kneecap is floating in fluid, indicating a significant effusion in the knee joint.

Diagnosis

• Clinical evaluation
• Radiographs to exclude fractures
• Sometimes MRI

Diagnosis of knee sprains and meniscal injuries is mainly clinical

Stress testing is usually delayed because the pain is initially very severe.

Spontaneous reduction of a knee dislocation should be suspected in patients with abundant hemarthrosis, macroscopic instability or both; a detailed vascular evaluation including ankle-arm index and CT angiography should be done immediately because injury to the popliteal artery is possible.

Afterwards, the knee should be fully examined.

Active knee extension is assessed in all patients presenting with knee pain and effusion to check for a rupture of the knee extensor mechanism (e.g. quadriceps tendon or patellar tendon tears, patella and tibial apophysis fracture).

Stress test

Stress testing to assess ligament integrity helps distinguish a partial tear from a complete one.

However, the test is usually postponed until radiographs are taken to exclude fractures if patients have significant pain and swelling or muscle contracture.

In addition, significant swelling and contracture may give stability to the joint making assessment difficult.

Such patients should be examined 2 to 3 days later (after the swelling and spasm have subsided).

A delayed objective examination of the knee is more sensitive than MRI of the knee (86% vs 76% [1]) for the diagnosis of meniscal and anterior cruciate ligament injuries.

Bedside stress testing is done to check for specific injuries, although most of these tests are not very accurate or reliable.

For bedside stress testing, the operators move the joint in a direction where the ligament being tested normally prevents excessive joint movement.

For the Apley test, the patient is in the prone position, and the examiner locks the patient’s thigh.

The examiner flexes the patient’s knee to 90° and rotates the leg while pressing the leg down towards the knee (compression), then rotates the lower leg while pushing it out of the knee (distraction).

Pain during compression and rotation suggest a meniscal injury; pain during knee extension and rotation suggest a ligamentous or joint capsule injury.

For assessment of the medial and lateral collateral ligaments, the patient is supine with the knee flexed approximately 20° and the posterior thigh muscles relaxed.

The examiner places one hand over the side of the knee opposite the ligament to be assessed.

With the other hand, the examiner locks the calcaneus and circles the lower leg either externally to assess the medial collateral ligament or internally to assess the external collateral ligament.

Moderate instability after an acute injury suggests that the meniscus or cruciate ligament is injured as well as the collateral ligament.

The Lachman test is the most sensitive clinical examination for acute anterior cruciate ligament injuries (2).

With the patient supine, the examiner supports the patient’s thigh and calf, and the patient’s knee is flexed to 20°.

The leg is moved anteriorly.

Excessive passive anterior movement of the tibia from the femur suggests a major tear.

Diagnostic imaging

Not all patients require radiographs.

However, anteroposterior, lateral, and oblique radiographs are often performed to exclude fractures.

The Ottawa knee rules are used to limit X-rays for patients most likely to have a fracture requiring specific treatment.

X-rays should only be taken if one of the following situations is present:

• Age > 55 years
• Isolated patella pain (with no other knee bone pain)
• Pain in the head of the fibula
• Inability to bend the knee to 90°.
• Inability to bear load for 4 steps immediately and in the emergency room (with or without lameness)

MRI is usually not necessary at initial assessment.

A reasonable approach is to do MRI if the symptoms do not resolve after a few weeks of conservative treatment.

However, MRI is often done when severe or significant intra-articular lesions are suspected or cannot be excluded by other means.

Other tests may be performed to check for related lesions:

• Arteriography or CT angiography to check for suspicious arterial lesions
• Electromyography and/or nerve conduction studies (rarely conducted immediately; more typically performed when nerve symptoms persist weeks to months after injury)

References for diagnosis of knee injury

1.  Rayan F, Bhonsle S, Shukla DD: Clinical, MRI, and arthroscopic correlation in meniscal and anterior cruciate ligament injuries. Int Orthop 2009 33 (1):129-132, 2009. doi: 10.1007/s00264-008-0520-4

2. Benjaminse A, Gokeler A, van der Schans CP: Clinical diagnosis of an anterior cruciate ligament rupture: A meta-analysis. J Orthop Sports Phys Ther 36(5):267-288, 2006.

Knee injuries and lacerations: treatment

• Mild sprain: PRICE (protection, rest, ice, compression and elevation) with previous immobilisation
• Severe injuries: a splint or knee brace and referral to an orthopaedic surgeon for surgical repair

Drainage of large effusions can reduce pain and spasm.

Contraindications to knee arthrocentesis include anticoagulation and cellulitis overlying the affected knee.

Most moderate Grade 1 and Grade 2 injuries can be treated initially with PRICE (protection, rest, ice, compression and elevation), including immobilisation of the knee in 20o flexion with a commercially available brace or splint.

Early movement exercises are usually recommended.

Severe 2nd degree and most 3rd degree injuries require a cast brace for ≥ 6 weeks.

Some 3rd degree injuries of the medial collateral ligament and anterior cruciate ligament require arthroscopic surgical repair.

Patients with severe injuries are referred to an orthopaedic surgeon for surgical repair.

Meniscal injuries vary greatly in their characteristics and treatments.

Large, complex, or vertical tears and injuries that result in persistent effusions or disabling symptoms are more likely to require surgery.

Patient preference may influence the choice of treatment.

Physiotherapy may be helpful, depending on the patient and the type of injury.

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Source:

MSD