Knee Dislocation – Causes, Symptoms, Diagnosis, Treatment

Knee Dislocation is a potentially devastating injury and is often a surgical emergency. This injury requires prompt identification, evaluation with appropriate imaging, and consultation with surgery for definitive treatment. Vascular injury and compartment syndrome are dreaded complications that the clinician should not miss in the workup of a knee dislocation. Note that this is in distinct contrast to patellar dislocations, which generally do not require immediate surgical or vascular intervention.[rx][rx]

A knee dislocation is a knee injury in which there is a complete disruption of the joint between the tibia and the femur. Symptoms include knee pain and instability of the knee. Complications may include injury to an artery around the knee, most commonly the artery behind the knee, or compartment syndrome.^[rx][rx][rx]

Types /Classification of Knee Dislocation

They may be divided into five types: anterior, posterior, lateral, medial, and rotatory. This classification is based on the movement of the tibia with respect to the femur. Anterior dislocations are the most common, followed by posterior dislocations. They may also be classified based on what ligaments are damaged.^[rx]

Kennedy classification based on the direction of displacement of the tibia

Anterior (30-50%)

• most common
• due to hyperextension injury
• usually involves tear of PCL
• an arterial injury is generally an intimal tear due to traction
• the highest rate of peroneal nerve injury

Posterior (30-40%)

• 2nd most common
• due to axial load to the flexed knee (dashboard injury)

The highest rate of vascular injury (25%) based on Kennedy classification

• has highest incidence of a complete tear of the popliteal artery

Lateral (13%)

• due to a varus or valgus force
• usually involves tears of both ACL and PCL

Medial (3%)

• varus or valgus force
• usually disrupted PLC and PCL

Rotational (4%)

• posterolateral is most common rotational dislocation
• usually irreducible
• buttonholing of femoral condyle through the capsule

Anatomic Classification System

The letters C and N can be added to denote arterial and neurologic injury, respectively.

Schenck Classification

• based on a pattern of multi ligamentous injury of knee dislocation (KD)

• Car accidents – If you bang your knee against a hard surface like your dashboard, the force of the blow may be strong enough to dislocate your knee.
• Sports injuries – This is less common than car accidents, but it’s possible to dislocate your knee if you collide with great force with another player or with the ground when your knee is bent, or if you over-extend your knee (bend it back farther than it’s supposed to go).
• Hard falls – It may happen to skiers or runners who lose control and fall on a bent or overextended knee. You may even dislocate your knee if you fall after stepping into a hole in the ground by mistake.
• Result of major trauma – and about half occur as a result of minor trauma.^[rx] Major trauma may include mechanisms like falls from a significant height, motor vehicle collisions, or a pedestrian being hit by a motor vehicle.
• Major trauma – often have other injuries.^[rx] Minor trauma may include tripping while walking or while playing sports. Risk factors include obesity.^[rx] The condition may also occur in a number of genetic disorders such as Ellis–van Creveld syndrome, Larsen syndrome, and Ehlers–Danlos syndrome.^[rx]
• Sudden forceful  fall down
• Road traffic accident
• Falls – Falling onto an outstretched hand is one of the most common causes of the broken or dislocation knee.
• Sports injuries – Many cervical spine fractures occur during contact sports or sports in which you might fall onto an outstretched hand — such as in-line skating or snowboarding.
• Motor vehicle crashes – Motor vehicle crashes can cause the knee dislocation to break, sometimes into many pieces, and often require surgical repair.
• Have osteoporosis –  a disease that weakens your bones
• Eave low muscle mass or poor muscle strength – or lack agility and have poor balance (these conditions make you more likely to fall)
• Walk or do other activities in the snow or on the ice – or do activities that require a lot of forwarding momenta, such as in-line skating and skiing.
• Previous fractures record.
• Wave an inadequate intake of calcium or vitamin D.
• Football or soccer, especially on artificial turf
• Athletic injury with a sports injury.

The ligamentum patellae. Attached above to the lower border of the patella and below to the tuberosity of the tibia. A continuation of the central portion of the common tendon of the quadriceps femoris muscle. The oblique popliteal ligament. A tendinous expansion derived from the semimembranosus muscle. It strengthens the posterior aspect of the capsule.

Symptoms of Knee Dislocation

• Symptoms include knee pain. The joint may also be obviously out of place. A joint effusion is not always present.^[rx]
• Hearing a “popping” sound at the time of injury
• Severe pain in the area of the knee
• A visible deformity at the knee joint
• Instability of the knee joint, or feeling like your knee joint is “giving way”
• Limitations in the range of movement of your knee
• Inability to continue with activities, whether they involve day-to-day tasks or sports
• Feeling the kneecap shift or slide out of the groove
• Feeling the knee buckle or give way
• Hearing a popping sound when the patella dislocates
• Swelling
• A change in the knee’s appearance — the knee may appear misshapen or deformed
• Apprehension or fear when running or changing direction.

Diagnosis of Knee Dislocation

Vascular exam (especially popliteal artery distribution)

Perfusion Assessment

• Dorsalis pedis pulse
• Posterior tibial pulse
• Capillary Refill
• Ankle-Brachial Index (ABI) – Normal ABI (as well as pulses, Capillary Refill) may not exclude popliteal artery disruption

Hard signs of vascular injury

• Distal pulse loss or ischemia (e.g. pallor, coolness)
• Active bleeding
• Expanding hematoma
• Palpable thrill or bruit over the popliteal artery

Neurologic Exam (especially peroneal nerve)

• First web space and dorsal foot sensation
• Ankle dorsiflexion

Multidirectional instability

• Multidirectional instability may be only finding if knee spontaneously reduced prior to presentation
• Three of four ligaments are likely injured (ACL Tear, PCL Tear, LCL tear, MCL tear)

Skin changes

• Dimple Sign – Anteromedial skinfold at medial joint line. Seen in posterolateral dislocation (not reducible without surgery)
• Skin necrosis – Entrapped skin at femoral condyle
• Overlying Laceration – Suggests open Knee Dislocation (accompanies 20-30% of Knee Dislocations)

Others exam may include

• Checking the pulse in several places on your leg and knee – This is called checking posterior tibial and dorsal pedal pulses, which are located in the region of the knee and foot. Lower pulses in your injured leg could indicate an injury to a blood vessel in your leg.
• Checking the blood pressure in your leg – Called the ankle-brachial index (ABI), this test compares the blood pressure measured in your arm to the blood pressure measured in your ankle. A low ABI measurement can indicate poor blood flow to your lower extremities.
• Checking your sense of touch or sensation – Your doctor will assess the feeling in the injured leg versus the unaffected leg.
• Checking nerve conduction – Tests like electromyography (EMG) or nerve conduction velocity (NCV) will measure the function of the nerves in your leg and knee.
• Checking your skin color and temperature – If your leg is cold or changing colors, there may be blood vessel problems.
• X-rays – These tests create clear pictures of bone. Your doctor may order x-rays to look for skeletal abnormalities in the knee, such as a shallow groove in the femur.
• Magnetic resonance imaging (MRI) scans – These scans create better pictures of the soft structures surrounding the knee, like ligaments. An MRI is seldom necessary because the doctor can usually diagnose a dislocated patella through an examination and x-rays. However, if your doctor needs additional, more detailed images, he or she may order an MRI.

^{Treatment of Knee Dislocation}

Nonoperative

• Immobilization – Your doctor may recommend that your child wear a brace for 3 to 4 weeks. This stabilizes the knee while it heals.
• Weightbearing –  Because putting weight on the knee may cause pain and slow the healing process, your doctor may recommend using crutches for the first week or two after the injury.
• Physical therapy – Once the knee has started to heal, your child’s doctor will recommend physical therapy to help your child regain normal motion. Specific exercises will strengthen the thigh muscles holding the knee joint in place. Your child’s commitment to the exercise program is important for a successful recovery. Typically, children return to activity 3 to 6 weeks after the injury.
• Emergent closed reduction followed by vascular assessment/consult – indications to considered an orthopedic emergency, vascular consult indicated if pulses are absent or diminished following reduction if arterial injury confirmed by arterial duplex ultrasound or CT angiography
• Immobilization as definitive management – successful closed reduction without vascular compromise, most cases require some form of surgical stabilization following reduction, outcomes of worse outcomes are seen with nonoperative management/prolonged immobilization will lead to loss of ROM with persistent instability.
• Rest Your Leg – Once you’re discharged from the hospital in a legislating, your top priority is to rest your and not further inflame the injury. Of course, the arm sling not only provides support, but it also restricts movement, which is why you should keep it on even during sleep. Avoiding the temptation to move your will help the bone mend quicker and the pain fades away sooner.

Medication

• Antibiotic – Cefuroxime or Azithromycin, or  Flucloxacillin or any others cephalosporin/quinolone antibiotic must be used to prevent infection or clotted blood remove to prevent furthers swelling and edema
• NSAIDs – Prescription-strength drugs that reduce both pain and inflammation. Pain medicines and anti-inflammatory drugs help to relieve pain and stiffness, allowing for increased mobility and exercise. There are many common over-the-counter medicines called non-steroidal anti-inflammatory drugs (NSAIDs). They include and Ketorolac, Aceclofenac, Naproxen, Etoricoxib.
• Corticosteroids – Also known as oral steroids, these medications reduce inflammation.
• Muscle Relaxants –  These medications provide relief from associated muscle spasms.
• Neuropathic Agents – Drugs(pregabalin & gabapentin) that address neuropathic—or nerve-related—pain. This includes burning, numbness, and tingling.
• Opioids – Also known as narcotics, these medications are intense pain relievers that should only be used under a doctor’s careful supervision.
• Topical Medications – These prescription-strength creams, gels, ointments, patches, and sprays help relieve pain and inflammation through the skin.
• Calcium & vitamin D3 – to improve bone health and healing fracture. As a general rule, men and women age 50 and older should consume 1,200 milligrams of calcium a day, and 600 international units of vitamin D a day.
• Glucosamine & Diacerein, Chondroitin sulfate – can be used to tightening the loose tension, cartilage, ligament, and cartilage, ligament regenerate cartilage or inhabit the further degeneration of cartilage, ligament
• Dietary supplement-to remove general weakness & improved health.
• Antidepressants – A drug that blocks pain messages from your brain and boosts the effects of endorphins (your body’s natural painkillers).

Surgical Treatment

Open reduction

• irreducible knee
• posterolateral dislocation
• open fracture-dislocation
• obesity (may be difficult to obtain closed)
• vascular injury

External fixation

• vascular repair (takes precedence)
• open fracture-dislocation
• compartment syndrome
• obese (if difficult to maintain reduction)
• polytrauma patient

Delayed ligamentous reconstruction/repair

• instability will require some kind of ligamentous repair or fixation
• patients can be placed in a knee immobilizer until treated operatively
• improved outcomes with early treatment (within 3 weeks)

Arthroscopy +/- open debridement

• Arthroscopic or open debridement with removal of any loose bodies may be necessary for displaced osteochondral fractures or loose bodies.

MPFL re-attachment or reconstruction (proximal realignment)

• Proximal realignment constitutes the reconstruction of the MPFL. In brief, to repair the ligament, a longitudinal incision is made at the border of the VMO, just anterior to the medial epicondyle. The ligament is usually re-attached to the femur using bone anchors. If the patient has had recurrent dislocations, then reconstruction may be necessary by harvesting gracilis or semitendinosus which are then attached to the patella and femur.
• Isolated repair/reconstruction of the MPFL is not a recommendation in those with bony abnormalities including TT-TG distance greater than 20mm, convex trochlear dysplasia, severe patella alta, advanced cartilage degeneration or severe femoral anteversion.[rx]

Lateral release (distal realignment)

• A lateral release cuts the retinaculum on the lateral aspect of the knee joint. The aim is to improve the alignment of the patella by reducing the lateral pull.

Osteotomy (distal realignment)

• Where there is abnormal anatomy contributing to poor patella tracking and a high TT-TG distance, the alignment correction can be through an osteotomy. The most common procedure of this type is known as the Fulkerson-type osteotomy and involves an osteotomy as well as removing the small portion of bone to which the tendon attaches and repositioning it in a more anteromedial position on the tibia.

Trochleoplasty

• Trochleoplasty is indicated in recurrent dislocators with a convex or flat trochlea. The trochlear groove is deepened to create a groove for the patella to glide through; this may take place alongside an MPFL reconstruction. Studies suggest it is not advisable in those with open growth plates or severely degenerative joints. This procedure is uncommon except in refractory cases.

Complications of Knee Dislocation

Vascular compromise

• incidence of – 5-15% in all dislocations. 40-50% in anterior or posterior dislocations
• risk factors – KD IV injuries have the highest rate of vascular injuries
• treatment-emergent vascular repair and prophylactic fasciotomies

Stiffness (arthrofibrosis)

• incidence – most common complication (38%)
• risk factors – more common with delayed mobilization
• avoid stiffness with early reconstruction and motion
• arthroscopic lysis of adhesion
• manipulation under anesthesia

Laxity and instability 

• incidence – 37% of some instability, however, redislocation is uncommon
• treatment – arthroscopic lysis of adhesion, manipulation under anesthesia

Peroneal nerve injury 

• incidence- 25% occurrence of a peroneal nerve injury, 50% recover partially
• posterolateral dislocations

Treatment

• A to prevent equinus contracture
• neurolysis or exploration at the time of reconstruction
• nerve repair or reconstruction or tendon transfers if chronic nerve palsy persists
• a dynamic tendon transfer involves transferring the posterior tibial tendon (PTT) to the foot

References

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