Brief anatomy and function

• Modified hinge type bicondylar synovial joint
• Knee joint per se is formed by lower end of femur, upper end of tibia and patella. So, it is combination of two joints named: Tibio-femoral & Patellofemoral

• Tibial condyles are relatively flat and femoral condyles are rounded. This makes articulation quite shallow. Meniscus deepen the tibial condyle and provide further stability
• Patella increases the lever arm of the quadriceps and hence, enhances the power of quadriceps
• Menisci are shock absorbers, deepen the articular surface, provide stability
• Cruciates, collaterals, capsule and surrounding muscle provide further stability
• Vasculature to the knee: anastomosis around the knee
• Nerve supply to the knee: femoral, common peroneal and tibial
• Major bursae: Prepatellar, infrapatellar, semimembranosus
• Normal alignment for a knee is 4-7⁰ of valgus.

• Muscles around Knee joint

 

Chief complaints

The patients with knee pathology mostly come up with few specific complaints.

1. Pain
2. Swelling
3. Deformity
4. Instability
5. Locking

1. Pain: Most common complaint

• Acute or chronic. Acute pain in

1. Traumatic: H/O frank trauma
2. Acute infection: septic arthritis
3. Exacerbation of chronic condition

• Aggravates with

1. iI pain aggravates only with attempted movements/weight bearing/squatting/sitting cross leg/walking/running; it is known as mechanical pain
2. If pain is present even during nights/rest, it indicates or suggestive of inflammation/infection/tumor

• Relieving factor:
• Rest: suggestive of mechanical pathology like osteoarthritis/meniscal tears
• not relieved on rest/even present during nights: suggestive of inflammation/infection/tumor

 

2. Swelling: It could arise within the joint or from extra-articular source (bone, tendon, nerve, vessels etc).

However, within the joint- reasons which could lead to swelling are

1. Effusion
2. Synovial hypertrophy.

OR It could be both.

Swelling immediately or within few hours after trauma indicates haemarthrosis whereas swelling after 12-24 hours of trauma indicates synovial reaction.

 

3. Instability: “My knee gives way” while running, jumping, stair climbing, walking on uneven ground etc. It indicates that one or more stabilizing ligaments of the knee are insufficient/torn. It mostly happens after major trauma or twisting injury.

Patella dislocation can happen even with minimal twisting injury.

An acute intraarticular ligament tear leads to inability to bear weight, stand and walk for few hours to days. Only later, patient regains his ability to bear weight.

4. Difficulty in movement: Loss of range of movement could be another complaint. It could be due to deformity, pain, swelling or mechanical block.

5. Locking: Feeling as if knee gets locked in a flexed position often. It is a true mechanical block to further movement in any direction, flexion/extension. It is observed in bucket handle tear of meniscus, loose bodies.

Pseudo-locking (no true mechanical locking but a mere muscular spasm not allowing further movement) is seen in patellofemoral arthritis.

 

 

General & systemic examination: It is important in systemic diseases affecting the knee joint like Rheumatoid arthritis, tuberculosis etc.

 

Local examination

The entire lower limb should be properly exposed.

1. Attitude: Usually knee examination is performed in supine. The attitude of the both lower limbs can be described.

 

2. Inspection (Look): From front, side and back

 

General aspects

• Gait
• Supine
  • Coronal plane deformities:

Varus/Valgus

• Sagittal plane deformity:

Flexion deformity/recurvatum

• Muscle wasting
• Limb length discrepancy
• Swelling
• Position of patella
• Scar, sinus, ulcer,
• Prone
  • Examination of popliteal fossa

3. Palpation

1. Local rise in temperature
2. Tenderness: always palpate in a sequence to look for

Tenderness over bony and soft tissue points

-  Fibular Head, Patella

- Tibial and femoral condyles

- Attachments of MCL, LCL, ITB

Specific point to palpate during knee examination are

    A) Joint line tenderness: indicates- arthritis, meniscal tear or midsubstance collateral injury

Method- The knee is flexed 90⁰. Then, using thumb the tibial tuberosity is palpated. The thumb is advanced above slightly medially until the thumb falls into soft spot adjacent to the patellar tendon in the joint. Further, the joint line is palpated medially. Similarly, the joint line is palpated laterally.

   B) Swelling: swelling of the joint arises due to synovial fluid or synovial hypertrophy or both

   C) Patellar tap: Assessed to guage the excess fluid in the knee joint in form of excess synovial fluid/haemarthrosis

Method- While the knee is in supine position, the fluid in suprapatellar fossa (4 finger above the superior border of patella) is squeezed into the joint using entire hand, and hand is held in same position just above the patella. Then tip of all fingers and thumb are placed over the anterior aspect of patella. Then, patella is pushed towards the femoral trochlea with a ‘jerk’. In case of excess fluid, the patella hits femoral trochlea and bounces back. Multiple repetitions confirm the tap.

   D) Crepitus: It is assessed while moving the knee though available range of movement by keeping the hand over the knee. Crepitus could be fixed

                  in its location where it is felt: This is observed in fixed lesions of cartilage and bone like osteoarthritis. Mobile crepitus where there is no                     specific location where it is felt. It may be felt or not intermittently is seen in case of loose bodies wherein a loose body creates                                    crepitus/click only when it is entrapped between the two articulating surface.

   E) Synovial hypertrophy:

Method- it is assessed while palpating over medial femoral condyle just medial to medial border of patella.

   F) Retropatellar tenderness:

Method- The examiner places his entire hand over the patella and gently presses it against the femoral trochlea.

In case of Retropatellar cartilage lesions, patient winces with pain.

   G) Facet tenderness:

Method- push the patella medially and place the finger under the medial facet and feel for tenderness with index finger. Similarly, push the patella laterally and feel for tenderness under the lateral facet with index finger.

   H) Palpating popliteal fossa

 

4. Movements:       Flexion: Normal range is 0-140⁰. It may be fewer degree less or more depending upon the bulk of thigh and calf.  Hyperextension, if any: Normally 0⁰ but occasionally it could be upto 10-20⁰

 

5. Measurement:

1. The length of the lower limb is measured in standard fashion. (ASIS to medial joint line; medial joint line to tip of medial malleolus)
2. Wasting of thigh and calf muscles
3. Q angle: It is the angle between quadriceps tendon and patellar tendon. It is a measure of lateral pull exerted on patella by quadriceps.

Method: Keep both lower limbs parallel to each other with quadriceps relaxed. Patella should be centered over the knee. Then a line is drawn from ASIS to the midpoint of patella. Another line is drawn from midpoint of patella to the tibial tuberosity. The angle between the intersection of two lines is the Q-angle

 

6. Neurovascular examination of lower limbs

 

7. Joint above and below: hip and ankle-foot

 

8. Special tests:

 

1. For instability of the knee:

There are four major ligaments in and around the knee (ACL, PCL, MCL, LCL) which should be tested for integrity and stability of the knee.

• Anterior cruciate ligament (ACL)

1. Lachman test: Very sensitive test for ACL tear. Useful in acute injuries of the knee.

Method- Knee is kept in 15-20⁰ flexion. The examiner stabilizes the thigh with one hand while other hand pulls the leg forward. Test is considered to be positive if there is soft end feel.

 

2. Anterior drawer’s test: Less sensitive than Lachman.

Method- Knee is flexed to 90⁰ and hip to 45⁰ and foot is placed over the couch. The examiner sits on the forefoot of the patient and stabilizes it. Then the examiner places both his hand around the upper end of tibia and pulls it forward.

 

3. Pivot shift test: Most specific test for the ACL tear.

Method: While keeping the knee in extension and internal rotation, valgus stress is applied to the knee and the knee is flexed. The knee reduces by 20-30⁰ of flexion by a click.

 

• Posterior cruciate ligament (PCL)

 

1. Posterior drawer’s test: Performed for PCL tear

Method- Knee is flexed to 90⁰ and hip to 45⁰. The examiner sits on the forefoot of the patient and stabilizes it. Then the examiner places both his hand around the upper end of tibia and pushes it backward.

 

2. Posterior sag sign

Method- Both the hip and knee are flexed to 90⁰ while leg is kept off the couch. Normally, the tibial shin is above the level of patella. However in case of PCL tear, the tibia sags downwards below the level of patella

 

• Medial/lateral collateral ligament (MCL/LCL)

 

1. Valgus stress test: For MCL tear

Method of Valgus stress test- Patient in supine position with knee extended. The examiner stands on lateral aspect of leg. Examiner holds the leg at the level of ankle while other hand is kept at the level of lateral aspect of the knee (over the lateral femoral condyle). A valgus tress is applied using the hand holding the ankle whereas the other hand at the level of femoral condyle acts as a fulcrum. In case of MCL tear, there is abnormal valgus opening.

The test is performed in 0⁰ extension and 30⁰ flexion.

If there is significant opening in extension, it indicates- tear of cruciate ligaments as well as posteromedial capsule too

If there is significant opening in flexion, it indicates- MCL tear alone

2. Varus stress test: for LCL tear

Method of varus stress test- Patient in supine position with knee extended. The examiner stands on lateral aspect of leg. Examiner holds the leg at the level of ankle while other hand is kept at the level of medial aspect of the knee (over the medial femoral condyle). A varus stress is applied using the hand holding the ankle whereas the other hand at the level of femoral condyle acts as a fulcrum. In case of LCL tear, there is abnormal varus opening.

This test is also performed in 0⁰ extension and 30⁰ flexion.

If there is significant opening in extension, it indicates- tear of cruciate ligaments as well as posterolateral capsule too

If there is significant opening in flexion, it indicates- LCL tear alone

 

 

2. For Meniscal tear

Many tests are performed for confirming the meniscal tear viz, McMurray’s test, Appley’s grinding test and Thessaly test.

 

1. McMurray’s test: performed for meniscal tear.

Method for McMurray for medial meniscus (MM)- patient is asked to flex his affected knee as much as possible. Then, examiner holds the ankle with one hand and other hand holds the lower end of thigh. Then, the leg is externally rotated and gently extended while giving a valgus stress test at the level of the knee. In case of MM tear, patient will wince with pain.

 

Method for McMurray for Lateral meniscus (LM)- patient is asked to flex his affected knee as much as possible. Then, examiner holds the ankle with one hand and other hand holds the lower end of thigh. Then, the leg is internally rotated and gently extended while giving a varus stress test at the level of the knee. In case of LM tear, patient will wince with pain.

 

2. Apley’s grinding test:

This test is not performed these days as there is an element of grinding involved.

However, it is useful test to differentiate between meniscal tear and mid-substance collateral ligament tear.

This test has two parts; Apley’s compression test and Apley’s distraction test.

Method: patient is made to lie prone and the affected knee is flexed to 90⁰. Then, examiner pushes the thigh against the couch and stabilises it while hold the leg just below the level of ankle.

Apley’s distraction test: Now, the leg is distracted and rotated internally as well as externally. Any pain in such situation is suggestive of collateral ligament injury as the injured ligament is stretched in ‘distraction’

Apley’s compression test: Now, the leg is pushed against the knee to ‘compress the menisci’ and rotated. This also relaxes the collaterals. If pain is elicited in this situation, it is due to the meniscal tear and not collateral.

 

3. For recurrent patella dislocation (RPD)

Apprehension test:

Method: The knee is kept in extension while patient is lying supine. Then, the patella is pushed laterally by the thumb of examiner while the knee is gently flexed from 0-30⁰.

In patients with RPD, the patient shows apprehension on his face and stops the examiner to further continuing flexion.

 

Common conditions affecting knee with salient features

1. Recurrent instability due to ligament tears (ACL/PCL/MCL/LCL/RDP/combination)

• Affects young patients
• May be associated ligament laxity
• H/O twisting injury/RTA
• Usually H/O inability to stand and walk after the injury, immediate swelling
• Pathologically: complete tear of the ligament
• Presents with: instability while running/jumping/pivoting sports/climbing stairs etc depending upon ligament injured
• Clinically: appropriate tests are positive
• Diagnosis: MRI
• Needs surgical repair/reconstruction: Arthroscopic/open

 

2. Osteoarthritis

• Affects adults and elderly: 50+ years

• Presents with: Mechanical pain, difficulty in walking, squatting, sitting cross leg
• Pathologically: loss of articular cartilage in the joint
• Clinically:

• Joint line tenderness
• Crepitus
• Painfully restricted ROM

• Diagnosis: Xray
• Treatment: NSAIDs, physiotherapy, intraarticular steroid or hyaluronic acid injection, arthroscopic debridement, Total knee replacement

 

3. Tubercular arthritis

• Affects any age
• Presents with: Night pain, deformity and loss of ROM, systemic features (fever/loss of weight, loss of appetite)
• Pathologically: three stages

• Stage of synovitis
• Stage of arthritis
• Stage of deformity

• Clinically:

• synovitis, features of arthritis
• triple subluxation in late stages: flexion, posterior subluxation and external rotation at the knee

• Diagnosis: Xray, MRI, synoval or bone biopsy
• Treatment: NSAIDs, physiotherapy, ATT, biaxial traction, arthrodesis and sometime total knee replacement.

 

4. Chondromalacia

• Affects young patients especially females
• Usually idiopathic
• Presents with: knee pain especially while keeping the knee bent, climbing stairs, squatting
• Pathologically: fraying and fibrillation of patellar cartilage
• Clinically: patellar facet and Retropatellar tenderness +
• Diagnosis: MRI
• Treatment: NSAIDs, physiotherapy. Usually self limiting by 6 months to few years. Rarely needs arthroscopic debridement of frayed cartilage.