Wednesday, January 25, 2017

Knee Ligaments Review

Knee Ligaments Review
  • Ottawa knee rules are less sensitive in children; use Pittsburgh rules to determine whether or not to obtain radiographs
  • MRI is 95% and 90% accurate in identifying ACL tears and meniscal injuries, respectively
  • Pain with varus or valgus stress is more suggestive of ligament damage than a meniscus tear
  • The MCL is the primary static stabilizer against valgus stress at the knee
  • The LCL is the primary static stabilizer against varus stress at the knee
  • The ACL is the primary static stabilizer of the knee against anterior translation of the tibia with respect to the femur
  • The PCL is the primary static stabilizer of the knee against posterior translation of the tibia with respect to the femur
  • WB, NWB = weight bearing or non weight bearing
  • Ligament injuries are graded as follows:
    • Grade 1: stretching of the ligament with no detectable instability
    • Grade 2: further stretching of the ligament with detectable instability, but with the fibers in continuity
    • Grade 3: complete disruption of the ligament.

Meniscal Tear
Acute: Twisting injury on weight bearing knee
Chronic: degenerative tears, mechanical grinding of osteophytes on meniscus

Late teens, peak (30-40)

MC: medial meniscus

1. Foot planted with femur rotated internally with valgus stress (medial) OR
2. Femur rotated externally with varus stress (lateral)

1. Most acute tears (younger pt) are vertical longitudinal or oblique tears
2. Complex and degenerative tears (older pt)
HX: axial loading with rotation or HX of osteoarthritis
1. Pain (variable)
-Event followed by insidious pain and swelling over 24 hours
-Worse with twisting or pivoting
-Mechanical SX: ”Tearing” or “popping” sensation: popping, locking, catching, or “knee giving out”; cannot extend fully
2. Effusion (common) -patient will complain of stiffness  

1. Joint line tenderness (sensitive, non specific)
2. Abnormal ROM: loss of smooth passive motion or full extension
-Locking, instability  
3. Inability to squat or kneel; can bear weight
4. Joint effusion
1. McMurray Maneuver: catching, pop, or click at joint line
2. Flexion McMurray: pain over posteromedial joint line
3. Apley grind test: pain at either joint line
4. Thessaly Test: shows pain

1. X-ray of knee: degeneration, calcification
2. MRI - most sensitive (confirm)
1. Rest, ice for 15 mins every 4-6 hours, elevate, crutches, patellar restraining brace
2. Steroid injection - only useful if patient has OA complicated by meniscal tear
3. Surgery if mechanical symptoms present
-If small <15 mm: heals spontaneously
-Repair larger tears
(a) Partial meniscectomy: short recovery
(b) Repair rather than meniscectomy (esp in young)

Health Maintenance
1. Tears that occur centrally have a longer healing rate
2. Return to full function may be expected in 6–8 weeks
3. High risk of OA if meniscectomy at young age
Anterior Cruciate Ligament (ACL) Tear
Occur with sudden deceleration with a rotational maneuver, usually without contact; OR contact injury with valgus force to extended knee

F > M

Associated: high incidence of lateral meniscal tears
HX: hyperextension and/or valgus force to knee by direct blow
1. “Pop” reported by patient
2.  Knee swelling within 4-12 hours of injury

1. Unable to fully bear weight (instability), knee giving out with twisting activities
1. Lachman Test
-Most sensitive for diagnosis
2. Anterior Drawer Test
3. Pivot Shift Test: helps evaluate rotational instability

1. XR: normal
2. MRI (confirms)
1. Supportive
-Pain relief with Tylenol +/- NSAID
-Limit ROM, place in long leg brace
-Obtain XR if indicated
-Consider MRI
2. Refer to Ortho
-Surgical repair once full ROM obtained
-Double-bundle reconstruction
-RTA in 4-6 months
-Physical therapy
Lateral Collateral Ligament (LCL) Injuries
“Knee buckling” into hyperextension with normal gait ‘

Associated: peroneal nerve injury (12-29%)
1. HX: valgus/varus stress to extended knee
2. Pain over lateral aspect of knee joint
3. Hemarthrosis

1. Able to bear weight without instability or locking
2. Laxity with varus stress testing with knee at 30 degrees flexion
3. Tenderness along lateral joint line
4. Neurovascular exam: r/o peroneal nerve injury
5. Dial test: most useful to evaluate for posterolateral instability
1. XR: normal or fibular head avulsions, patellar dislocation, loose bodies; lateral joint space narrowing with osteophytes and subchondral sclerosis
2. MRI: abnormal
1. Supportive
-Pain relief with Tylenol +/- NSAID
-Limit ROM, place in long leg brace
-Obtain XR if indicated
-Consider MRI
2. Refer to Ortho
-All start early PT
-Grade I: 2-4 weeks immobilization → Quad strengthening
-Grade II: brace blocking last 20 degrees of flexion, WBAT
-Grade III: surgery

Health Maintenance
1. Limit weight bearing after surgery for 6 weeks, brace for at least 3 weeks
Medial Collateral Ligament (MCL) Injuries
MCL is primary restraint to valgus stress, attached to medial meniscus at joint line

Forced abduction of leg at knee

Associated: tear of medial meniscus and rupture of ACL (look for immediate swelling)
1. HX twisting injury or direct blow at knee with valgus strain
2. Pain over medial aspect of knee joint
3. Joint effusion if severe

1. Medial joint line tenderness
2. Patellar apprehension test
-Check for patellar dislocation
3. Laxity to valgus stress at 30 degrees of flexion
1. XR: not helpful unless made with valgus stress applied
2. MRI - r/o concomitant meniscal injury (confirms)
1. Supportive
-Pain relief with Tylenol +/- NSAID
-Limit ROM, place in long leg brace
-Obtain XR if indicated
-Consider MRI
2. Refer to Ortho
-All start early PT
-Grade I: WBAT, early amb
-Grade II: brace blocking last 20 degrees of flexion, WBAT
-Grade III: hinged brace, initial NWB, advance WB over 4 weeks
Posterior Cruciate Ligament (PCL) Tear
Most common mechanism of injury: direct blow to anterior tibia with knee flexed or fall to ground with foot plantar flexed

Associated: posterolateral corner (meniscus) tear (60%)
1. Knee pain
- Biggest complaint
2. Swelling
3. Stiffness

1. Abrasions or ecchymosis around proximal anterior tibia
2. Ecchymosis in popliteal fossa
3. Instability
1. Posterior Drawer Test
2. Posterior Sag (Godfrey) Test
3. Reverse Pivot Test

1. MRI
1. Non-surgical
-Obtain full quad strength
-Grade I/II: early motion, WBAT
-Grade III: keep knee immobilized in extension
-Surgery to prevent osteoarthritis or instability

Health Maintenance
1. Bracing is ineffective
2. Minimum 3 months rehab before return to play  
  • Thessaly Test: have patient hold your hand and have patient stand on one leg with knee flexed to 20 degrees, then patient will internally and externally rotate their knee
    • Pain or locking/catching sensation = (+) test, 90% sensitive, 96% specific
  • McMurray Test: repeated passive flexion and extension of knee; painful click in early or mid extension of the knee = meniscal tear
    • Grasp patient’s heel with one hand and place fingers and thumb of other hand along joint line; passively flex knee and internally rotate tibia; extend the knee while maintaining internal rotation; passively flex the knee while externally rotating
    • Sensitivity: 50%, specificity 60-97%
  • Apley Test: patient prone with affected knee flexed 90 degrees, stabilize thigh with a knee or hand; press patient’s heel toward the floor while internally and externally rotating the foot; pain = (+) test
    • Sensitivity: 38-41%
  • Lachman Test: Knee flexed at 20 degrees, stabilizing the distal femur with one hand and pulling forward on the proximal tibia with the other hand
  • Anterior Drawer Test: With the patient supine and the knee flexed to 90 degrees (hip flexed to about 45 degrees), the foot is restrained by sitting on it and the examiner's hands are placed around the proximal tibia. Then, while the hamstrings are felt to relax and the tibia is pulled forward, the displacement and the end point are evaluated.
  • Pivot Shift (Losee) Test: a valgus and internal rotation force is applied to the tibia; Starting at 45 degrees of flexion, the lateral tibial plateau is reduced. Extending the knee causes the lateral plateau to subluxate anteriorly with a thud at about 20 degrees of flexion. It reduces quietly at full extension
  • Posterior Drawer Test: The posterior drawer test evaluates the integrity of the PCL. It is performed with posterior pressure on the proximal tibia with the knee flexed at 90 degrees and
  • Posterior Sag (Godfrey) Test: This test involves flexing the knee and hip and noting the posterior pull of gravity creating posterior “sag” of the tibia on the femur
  • Dial Test: externally rotate each tibia and note the angle subtended between the thigh and the foot. The dial test is performed at 30 and 90 degrees of flexion with a significant difference being an angle 5 degrees or greater than the contralateral leg. Injury to the posterolateral capsule alone is confirmed with greater external rotation at 30 degrees, an isolated PCL at 90 degrees, and to both structures when there is greater rotation at 30 and 90 degrees compared to the uninjured leg

Obtain X-ray for:
Ottawa Knee Rules
Pittsburg Knee Rules
Greater specificity
1. Age >55
2. Tenderness to head of fibula
3. Isolated tenderness to patella
4. Inability to flex knee to 90 degrees
5. Inability to bear weight for 4 steps both immediately and in examination room regardless of limp
1. Recent fall or blunt trauma
2. Age <12 y/o or >50 y/o
3. Unable to take 4 unaided steps

Please enjoy these free TrueLearn questions below and check out the link above for more!

Question 1: A 40-year-old man presents to the office complaining of right knee pain for the past three days after a weekend football game in his neighborhood. He fell with his knee in extension after being tackled and felt a sudden sharp pain as he hit the ground. Afterwards, he could not stand on the knee and has been taking acetaminophen and using ice packs to help reduce the swelling. He is in moderate pain and cannot walk up and down stairs in his house. On examination, the right knee is red and swollen with a mild effusion anteriorly. The left knee appears normal. There is mild tenderness to palpation diffusely. There are no sites of penetration or fluctuance. A Lachman’s test is positive. Which of the following is the most likely diagnosis for this patient?
  1. Anterior cruciate ligament injury
  2. Lateral collateral ligament injury
  3. Medial collateral ligament injury
  4. Medial meniscus injury
  5. Posterior cruciate ligament injury

The most common set of knee injuries are the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus (the unhappy triad of knee injuries). The ACL provides anterior stability to the knee and is injured in periods of hyperextension. It originates at the posteromedial aspect of the lateral femoral condyle and courses in an anterior and medial fashion to the anteromedial aspect of the tibia between the condyles, as shown below. Patients report a sharp sudden pain as the ligament is torn. The Lachman’s test is specifically designed to evaluate the anterior cruciate ligament. During the test, a patient lays supine with the knee flexed at 20º while the examiner pulls anteriorly with the tibia and stabilizes the femur. The anterior drawer sign can also be used to evaluate ACL injury as the patient lays supine with the knee flexed at 90º and the hips flexed at 45º. The examiner pulls the tibia forward and, similar to the Lachman’s test, will note hypermobility anteriorly if there is an injury.

Answer B: The lateral collateral ligament can be examined with Varus stress on the knee. If damaged, the physician will note hyperlaxity with the stress.
Answer C: A medial collateral ligament injury can be diagnosed with Valgus stress and injury is noted if there is hyperlaxity in relation to the medial aspect of the knee.
Answer D: The medial meniscus can be evaluated by the McMurray’s test. The patient lies flat and the examiner flexes the knee. A click may be felt on the medial joint line. Then, the foot is torqued medially as the knee is rotated laterally in order to trap the meniscus and note further pain and clicking. The directions can be reversed for evaluating the lateral meniscus.
Answer E: The posterior drawer sign can be elicited to evaluate for a posterior cruciate ligament injury. The knee is flexed at 90º with the hips flexed at 45º as the tibia is pushed posteriorly against a fixed femur. Posterior hyperlaxity will be noted if there is an injury.

Bottom Line: The ACL tear is one of the most common knee injuries and can be diagnosed by the Lachman’s and anterior drawer tests. Treatment is surgical if the patient intends to return to the sport or strenuous activities. The following links are some videos to help with understanding the various physical exam maneuvers for diagnosing knee injuries.

For more information, see:

Question 2: A 39-year-old male presents to the office with the complaint of left knee pain and swelling for five days' duration. He denies fevers, chills, or other joint involvement. History reveals the presence of locking and popping in the left knee that began while playing flag football. At this time, he felt a pop and had immediate pain and swelling. The symptoms initially improved with ice, then became more painful. Physical examination reveals the left knee is warm to the touch, swollen, and very tender to palpation along the joint line. Further examination reveals a positive McMurray test. The most appropriate test to confirm the diagnosis is a

  1. bone scan of the lower extremity
  2. computed tomography with contrast of the lower extremity
  3. magnetic resonance imaging of the lower extremity
  4. ultrasound of the lower extremity
  5. radiograph of the lower extremity

This patient is suffering from a torn meniscus. The medial meniscus is torn three times more commonly than the lateral meniscus. However, when the ACL is torn, the lateral meniscus is more commonly involved, such as in the terrible triad of the knee (ACL, MCL and lateral meniscus). Traumatic meniscal tears occur more commonly in young, athletic adults, while degenerative meniscal tears occur more often in older patients. Meniscal injuries are typically due to a twisting moment about the knee while it is under load, such as when a football player makes a turn while running. The McMurray test recreates the forces that cause the tear. This is done by having the patient supine with the affected knee flexed to 90 degrees with a valgus stress applied, then externally rotating and extending the knee. A positive test is indicated by pain or a “click”. The diagnostic test of choice is a magnetic resonance imaging (MRI). MRI is the test of choice for ligament injuries, meniscal disease, avascular necrosis, and articular cartilage defects of the knee.

Answer A: Bone scans are useful in diagnosing stress fractures, but not particularly helpful for meniscal tears.
Answer B: Computed tomography (CT) scans have been largely replaced by MRI for the evaluation of soft tissue structures, such as the fibrocartilage in the meniscus. Though, they remain useful for the evaluation of bony tumors and fractures.
Answer D: Ultrasound is beneficial for evaluating soft tissue lesions about the knee, such as patellar tendonitis, hematomas and extensor tendon ruptures.
Answer E: Radiographs are an initial diagnostic modality that will be performed to rule out bony injury, however they will not provide the soft tissue imagery necessary to diagnose a torn meniscus.

Bottom Line: An MRI is the diagnostic study of choice to evaluate meniscal injuries of the knee. For more information, see: Ayala C, Spellberg B. Boards and Wards. 4th Ed. Philadelphia, PA; Lippincott Williams & Wilkins; 2010: 201. Le T, Bhushan V, Skapik J, et al. First Aid for the USMLE Step II 2007: A Student-to-Student Guide. New York, NY: McGraw-Hill; 2007: 245 "Meniscal Injuries" on Medscape. "Meniscal injury of the knee" on UpToDate. Miller MD, Thompson SR, Hart JA, et al. Review of Orthopaedics. Philadelphia, PA: Elseiver-Saunders; 2012: 294 Updated: September 19, 2012

Question 3: A 35-year-old man complains of a painful and swollen right knee that began after playing ice hockey three days ago. He fell on his knee during the game and had difficulty playing the rest of the game. He has had severe difficulty walking down stairs for the last three days and has been using ice packs frequently to help reduce the swelling. He denies any fever or chills. His medical history is only significant for a splenectomy after being involved in a car accident 10 years ago. On examination, the entire right knee is edematous in comparison to the left, without erythema or warmth. There is tenderness to palpation of the medial side of the knee and valgus stress causes pain and increased motion at the knee joint. Which of the following is the most important step in managing this patient?

  1. Corticosteroids
  2. Immobilization and observation
  3. Joint fluid aspiration
  4. MRI of the knee
  5. X-ray of the knee

This patient with a history of trauma and pain on palpation on the medial aspect of the knee most likely has a medial collateral ligament tear. The medial collateral ligament is part of the “unhappy triad” (anterior collateral ligament, medial meniscus, and medial collateral ligament) most commonly injured in knee trauma. These structures are most commonly injured because knee injuries occur most commonly following valgus stress. In order to visualize the soft tissue structures of a knee, patients require an MRI. The MRI will show the ligaments and reveal any tears.

Answer A: Patients with chronic arthritis may require corticosteroid injections. Patients should not receive more than one injection per month for seriously affected joints. This plays no role in treatment of an acute injury due to trauma.
Answer B: Immobilization would not be best because a diagnosis has not been made. Many medial collateral ligament injuries are partial tears and will require an immobilizer brace, but this should only be utilized if the diagnosis is confirmed by imaging.
Answer C: Joint fluid aspiration is utilized for infected joints. Although this joint is swollen, it is not fluctuant or warm. Though a history of splenectomy may suggest a higher risk for infection, this patient does not exhibit the classic signs or symptoms of a septic joint. This patient has a known traumatic incident, not an infectious etiology from a puncture or systemic infection.
Answer E: An x-ray is useful for evaluating any breaks or osteoarthritis but not for visualizing the ligaments.

Bottom Line: Medial collateral ligaments are commonly injured and present with pain on palpation of the medial side and hyper-laxity of the joint with valgus stress due to increased instability.

TrueLearn Insight : Know the difference between varus and valgus stress. The below image shows valgus stress (Remember the L in the vaLgus is for Lateral force). For more information, see

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