A dislocated knee (tibiofemoral dislocation) is rarer and more serious than a dislocated kneecap, because of the force required to misalign the leg bones and the damage, it does to the ligaments. A tibiofemoral dislocation is a formal name for a dislocated knee. It’s a fairly rare injury, but a serious one. On the inner side is the medial tibiofemoral compartment and on the outer side is the lateral tibiofemoral compartment. A tibiofemoral dislocation can cause damage to the structures that support your knee. This may result in joint instability, which can be a long-term problem. Symptoms a “popping” sensation, severe knee pain, being unable to straighten the knee, and the sudden swelling of the knee.
Pathophysiology
- Definition
- Not all patients will present with an acutely dislocated knee or with an obvious deformity
- Often, knee dislocation will reduce spontaneously or easily
- Direction of dislocation
- Anterior (40%), due to forced hyperextension
- Posterior (30%), common mechanism tibia impacting the dashboard during deceleration in motor vehicle accidents
- Medial (18%)
- Lateral (4%)
- Rotational (less than 5%)
Etiology
- High energy trauma including motor vehicle accidents, falls from height, and industrial injuries
- Can occur in lower energy sports and sport-related activities
- Spontaneous injuries during ambulation in the morbidly obese
Associated Injuries
- Most commonly injured are the major knee stabilizers
- Multi Ligament Knee Injury, often bicruciate, including ACL + PCL + LCL/MCL
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Biceps tendon avulsions
- Popliteus tendon tears
- Arcuate complex injuries
- Less commonly injured orthopedic structures
- Meniscal Tear in about 50% of cases
- Chondral injuries
- Bone bruises are seen in the majority of cases
- Fractures are seen in about 1/3 of cases
- Extensor Mechanism Injuries
- Sports with reported cases
- Soccer
- Wrestling
- Rugby
- Kabaddi
- Long jump
- Skating
- Cycling
- Skiing
- Gymnastics
- Motorsports
- Extreme adventure sports
- Other
- Morbid Obesity is a risk factor for low energy mechanism
Differential Diagnosis
- Fractures
- Distal Femur Fracture
- Patellar Fracture
- Tibial Plateau Fracture
- Dislocations & Subluxations
- Patellar Dislocation (and subluxation)
- Knee Dislocation
- Proximal Tibiofibular Joint Dislocation
- Muscle and Tendon Injuries
- Quadriceps Contusion
- Iliotibial Band Syndrome
- Quadriceps Tendonitis
- Patellar Tendonitis
- Popliteus Tendinopathy
- Extensor Mechanism Injury
- Patellar Tendon Rupture
- Quadriceps Tendon Rupture
- Patellar Fracture
- Ligament Pathology
- ACL Injury
- PCL Injury
- MCL Injury
- LCL Injury
- Meniscal Pathology
- Posterolateral Corner Injury
- Multiligament Injury
- Arthropathies
- Knee Osteoarthritis
- Septic Arthritis
- Gout
- Bursopathies
- Prepatellar Bursitis
- Pes Anserine Bursitis
- MCL Bursitis
- Infrapatellar Bursitis
- Patellofemoral Pain Syndrome (PFPS)/ Anterior Knee Pain)
- Chondromalacia Patellae
- Patellofemoral Osteoarthritis
- Osteochondral Defect Knee
- Plica Syndrome
- Infrapatellar Fat Pad Impingement
- Patellar Instability
- Neuropathies
- Saphenous Nerve Entrapment
- Other
- Bakers Cyst
- Patellar Contusion
- Pediatric Considerations
- Patellar Apophysitis (Sinding-Larsen-Johansson Disease)
- Patellar Pole Avulsion Fracture
- Tibial Tubercle Avulsion Fracture
- Tibial Tuberosity Apophysitis (Osgood Schalatters Disease)
Diagnosis
- History
- Most commonly high energy trauma and deformity of the knee
- May also report lower energy mechanism with pain +/- deformity
- Also endorses instability if attempting to ambulate
- Physical Exam: Physical Exam Knee
- About 50% of cases will have no obvious deformity and gross appearance may be normal!
- Dimple Sign: buttonholing of medial femoral condyle through a medial capsule
- Very important to document a thorough vascular exam
- The presence of peripheral pulses does not exclude vascular injury
- A serial vascular exam is mandatory
- Assess Peroneal Nerve, Tibial Nerve
- Special Tests
- Ankle Brachial Index: can be used to compare vascular flow to the contralateral limb
- Need to perform structural exam assessing ACL, PCL, MCL, and LCL
Ankle Brachial Index
- Excellent screening tool since arteriography is impractical in all patients
- If ABI < 0.9, must pursue further vascular workup
- Mills et al: ABI <0.9 has 100% sensitivity, specificity, and PPD for vascular injuries in knee dislocations[10]
Radiographs
- Standard Radiographs Knee
- It May be normal depending on the mechanism
- look for asymmetric, irregular or widening joint space
- Segunda Fracture, Osteochondral Defect may be seen
- Post reduction or post splinting films are necessary
MRI
- Indicated in most cases
- After reduction, prior to surgical intervention if possible
- Helpful to identify the degree of soft tissue injury
- Especially in the multi-ligament knee injury
- Consider angiography
CT
- Useful to evaluate for fracture patterns
- Findings
- Tibial eminence fracture
- Tibial tubercle fracture
- Tibial Plateau fracture
- Consider angiography
Ultrasound
- Duplex arterial sonography may be useful to evaluate arterial supply
Classification
Kennedy Position Classification
- Anterior
- Frequency: 40% (most common)
- Mechanism: Hyperextension
- Typically no medial or lateral damage
- PCL can be intact
- Vascular injury is common
- Posterior
- Frequency: 30%
- Mechanism: Direct anterior-posterior force
- Sometimes ACL is intact
- Vascular damage is common
- Lateral/ Lateral
- Frequency: Rare in isolation (often with anterior or posterior)
- Most of the time is posterolateral or posteromedial
- Bicruciate injury with ACL and PCL
- Vascular damage
- Nerve damage in medial dislocations
- Rotatory
- Frequency: Rare
- Often complex lesions
Schenck Anatomic Knee Dislocation (KD) Classification
- KD I: Knee dislocation with either cruciate intact
- KD II: Bicruciate with collateral intact
- KD III: Bicruciate injury with one collateral ligament injury
- KD IIIM: Bicruciate + MCL injury
- KD IIIL: Bicruciate + LCL injury
- KD IV: Bicruciate with both collateral ligaments injured
- KD V: Periarticular fracture-dislocation
Treatment
Prognosis
- Levy et al systematic review compared operative to nonoperative management[11]
- Overall, operative treatment results in the better functional outcomes as compared to nonoperative treatment
- International Knee Documentation Committee [IKDC] excellent/good results 58% operative vs 20% nonoperative
- Return to sport is 29% in operative group vs 10% in the nonoperative group
- Range of motion (126° vs. 123°) and flexion (4° vs. 3°) loss was similar among groups
- Levy looked at the timing of surgery[12]
- More likely to return to sport if surgery is done within 3 weeks
- No difference in functional outcomes between early and late surgery
Acute
- Follow ATLS protocol when appropriate
- Physicians should be suspicious based on mechanism and examination, regardless of whether the deformity is present or not
- Reduction
- Perform after XR only to confirm the diagnosis, exclude fracture
- Recommend procedural sedation
- The gentle extension is often all that is required
- Will often self reduce with minimal manipulation
- Examination
- Thorough structural examination
- Confirm palpable dorsalis pedis, posterior tibia, and popliteal artery pulses
- Immobilization
- Full-extension in long Hinged Knee Brace or Posterior Long Leg Splint
- If the posterior capsule is injured, may require 20° of flexion to avoid posterior subluxation
- May require temporary external fixation
- Imaging
- Pre and post-reduction radiographs
- Consider CT (with angiography), emergent MRI
- Vascular- consider ABI, duplex arterial sonography
- Emergent surgery
- Irreducible knee dislocation
- Open knee dislocation
- Vascular injury
Nonoperative
- Indications
- Elderly
- Patients who are not good surgical candidates or have multiple comorbidities
Operative
- Indications
- Most patients
- Open reduction indications[13]
- Irreducible knee
- Posterolateral dislocation
- Open fracture-dislocation
- Obesity (may be difficult to obtain closed)
- Vascular injury
- External fixation indications
- Vascular repair (takes precedence)
- Open fracture-dislocation
- Compartment syndrome
- Obese (if difficult to maintain reduction)
- Polytrauma patient
- Delayed ligamentous reconstruction/repair
Complications
- Amputation
- The rate reported to be up to 85% for injuries not corrected in 8 hours[4]
- Traumatic Osteoarthritis
- Chronic pain
- 25% to 68% complain of chronic pain
- Arthrofibrosis
- 5% to 71% develop arthrofibrosis making it the most common complication
- 29% of patients will eventually require adhesiolysis
- Knee stiffness
- Higher risk with 3 or more ligaments repaired
- Persistent knee instability
- Instability in at least one plane ranges from 18% to 100% (mean 42%)
- Popliteal Artery injury
- Reported in 18 to 64% of knee dislocations[14]
- Approximately 80% are repaired, 12% require amputation
- Lower risk in sports-related injuries than high-velocity injuries[15]
- Early interventions within 8 hours (11%) are associated with lower rates of amputation than beyond (86%)[16]
- The highest risk with KD IV injuries
- McDonough case series on popliteal artery injuries following MLKI[17]
- 4/12 identified by physical exam, 5/12 identified with arteriography, and 3/12 identified in OR with vascular exam and arteriography
- Peroneal Nerve Injury
- Most commonly the Common Peroneal Nerve, however Superficial Peroneal Nerve, Deep Peroneal Nerve also affected
- Injured in between 25% and 33% of dislocations, particular posterior and lateral[18][19]
- As high as 41% in posterolateral corner injuries[20]
- Among sports, skiing and football are most commonly associated[21]
- Approximately 30% have a complete palsy, with only 38.4% of them having a functional recovery
- Approximately 70% have an incomplete palsy, and 87.3% of them have a functional recovery
