Knee Lab: Examination

Knee Lab: Examination Overview

Instructor: Dr. Daniel Maddox, PT, DPT, DSc
Credentials: Board Certified Orthopaedic Clinical Specialist (OCS); Fellow, American Academy of Orthopaedic Manual Physical Therapists (FAAOMPT)

General Observation

The clinician should examine the patient for all factors previously discussed in clinical evaluation, including:
- Posture: Overall alignment and positioning.
- Somatotype: Body build and physical characteristics.
- Muscle Tone: Resting state and density of musculature.
- Demeanor: Patient personality and behavioral responses.
- Integument: Skin health, scars, or disruptions.
- Etc…: Other standard physical observations.

Specific Postural Observations in the Knee

Genu Valgus

Definition: An abducted tibia in relation to the femur (often referred to as "knock-kneed").
Causation: Clinicians must consider potential structural or biomechanical causes for this alignment.
Objectifying Genu Valgus:
- Standard Position: The patient stands with knees and ankles as close together as possible.
- Measurement: If the knees touch but the ankle malleoli are $> 9-10\,cm$ apart, it is classified as Genu Valgus.

Genu Varus

Definition: An adducted tibia in relation to the femur (often referred to as "bow-legged").
Causation: Clinicians must consider potential structural or biomechanical causes for this alignment.
Objectifying Genu Varus:
- Standard Position: The patient stands with knees and ankles as close together as possible.
- Measurement: If the ankles touch but there is a gap of $> 4\,cm$ between the knees, it is classified as Genu Varus.

Genu Recurvatum

Definition: Knee Hyperextension.

Foot Alignment

Foot alignment may directly affect the knee, specifically the patellofemoral joint (PFJ).
Example Case: Clinical consideration must be given to what knee changes occur in the case of foot overpronation (e.g., increased internal rotation and valgus stress).

Functional Tests and Demonstrations

Functional Demonstration ("Show Me"): The Subjective Examination (SE) guides the selection of movements, but commonly utilized simple functional tests include:
- Observation of Gait.
- Observation of squatting and transfers (e.g., sit-to-stand).
- Observation of single leg stance (SLS).
- Observation of step-up and step-down maneuvers.

Neurological Screening

Dermatomal Sensory Assessment

Testing of sensory distribution for the lower extremity.

Deep Tendon Reflex (DTR) Testing

Patellar Reflex: Testing spinal levels $L3-L4$ .
Achilles Reflex: Testing spinal level $S1$ .

Myotomal Strength Testing

These tests may be performed later in the physical examination to assess motor output:
- L2: Hip Flexion
- L3: Knee Extension
- L4: Ankle Dorsiflexion (DF)
- L5: Great Toe Extension
- S1: Great Toe Flexion
- S2: Knee Flexion

Regional Screening

Screening is required for all regions that could be implicated in the patient's symptoms.
Active Movements: Perform movement in cardinal planes (e.g., flexion/extension) followed by manual overpressure.
Combined Planes: Perform active movements in combined planes followed by manual overpressure.
Ruling Out Competing Hypotheses: Utilize other regional screening tools as necessary.
Resistance Testing: To assess the integrity of contractile tissues.
Passive Accessory Mobility Assessment: To assess joint arthrokinematics.

Palpation: Key Structures

Musculature

Distal Quadriceps
Tibialis Anterior
Hamstring Tendons
Gastrocnemius (Gastroc) Origins and Heads

Bony Structures

Patella
Tibial Tubercle
Gerdy’s Tubercle
Fibular Head
Femoral Epicondyles
Adductor Tubercle
Medial and Lateral Joint Lines
Patellofemoral Joint (PFJ) Joint Lines

Tendons

Quadriceps (Quad) Tendon
Iliotibial (IT) Band
Pes Anserine

Other Relevant Structures

Medial Collateral Ligament (MCL)
Lateral Collateral Ligament (LCL)
Medial Meniscus
Lateral Meniscus
Popliteal Artery
Tibial Nerve
Common Fibular Nerve

Physical Examination: Active and Passive Movements

Movements are assessed actively, then passively, and then with overpressures (OP):
- Flexion
- Extension
- Internal Rotation
- External Rotation
- Combined Movements:
  - Extension / Internal Rotation / Adduction (EXT/IR/ADD)
  - Extension / External Rotation / Abduction (EXT/ER/ABD)
  - Flexion / External Rotation / Adduction (FLEX/ER/ADD)
  - Flexion / Internal Rotation / Abduction (FLEX/IR/ABD)

Accessory Mobility Testing

Tibiofemoral Joint

Anterior-Posterior (AP) Glide
Posterior-Anterior (PA) Glide
Internal Rotation (IR)
External Rotation (ER)

Patellofemoral Joint

Superior Glide
Inferior Glide
Medial Glide
Lateral Glide

Tibiofibular Joint

Anterior Glide
Posterior Glide

Note: Clinicians should also consider mobility testing that stresses specific tissues implicated by the patient's history. Formal ligamentous stress tests are often categorized under Special Tests.

Resistive Testing / Manual Muscle Testing (MMT)

Muscle groups to assess for strength and provocation:
- Quadriceps (Quads)
- Hamstrings
- Gluteus Maximus (Glute Max)
- Gluteus Medius (Glute Med)
- Tibialis Anterior
- Gastrocnemius (Gastroc)
- Soleus
- Tibialis Posterior
- Fibularis Longus
Consider performing Muscle Length Testing alongside resistance testing.

Neural Tissue Assessment

Sciatic Nerve

Basic Test: Straight Leg Raise (SLR) – hip flexion while maintaining full knee extension.
Additional Sensitizers:
- Ankle Dorsiflexion
- Hip Internal Rotation
- Hip Adduction

Femoral Nerve

Tests:
- Prone Knee Bend (PKB)
- Side-lying Knee Bend (SKB)
- Slumped position with the opposite knee pulled to the chest and the head flexed.
Technique: Flex the knee into hip extension. Add or remove cervical (cx) flexion to differentiate between neural tension and muscular tension.

Saphenous Nerve

Positioning: Patient is prone in hip Abduction (ABD) and Extension (EXT).
Test Components: Knee Extension, Hip Internal Rotation, and Ankle Plantarflexion (PF)/Eversion.

Special Tests: Principles and ACL Integrity

Principles of Diagnostic Utility

Sensitivity ( $Sn$ ): Range $0\% - 100\%$ . SnOut: High sensitivity means a negative result is good for ruling a condition out.
Specificity ( $Sp$ ): Range $0\% - 100\%$ . SpIn: High specificity means a positive result is good for ruling a condition in.

ACL: Lachman Test

Positive Finding: Excessive movement and/or a lack of a firm end feel.
Sensitivity: $\approx 85\%$
Specificity: $\approx 94\%$
Notes: Findings across studies vary widely; there are noted issues with inter-rater reliability.

ACL: Active Lachman Test

Positive Finding: Excessive anterior glide of the lateral tibial condyle compared to the contralateral side.
Sensitivity: Unknown ( $?$
Specificity: Unknown ( $?$
Notes: Studied only once. While that study indicated $100\%\,Sp$ , it lacked a valid reference standard.

ACL: Anterior Drawer Test

Positive Finding: Excessive movement and/or lack of end feel.
Sensitivity: $\approx 25\%$
Specificity: $\approx 96\%$
Notes: Consistently shown to be more specific than sensitive.

ACL: Pivot Shift Test

Positive Finding: A sudden reduction or "clunk" as the knee moves into flexion while maintains tibial Internal Rotation (IR) and a valgus force.
Sensitivity: $\approx 24\%$
Specificity: $\approx 98\%$
Notes: PhysioU video incorrectly states this is sensitive; it is actually a highly specific test.

Special Tests: PCL and Collateral Ligament Integrity

PCL: Posterior Sag Test / ‘Godfrey’s Sign’

Positive Finding: One tibial plateau sags lower than the other.
Extra Phase: Quadriceps contraction results in anterior translation back to "normal," or Hamstring (HS) contraction causes deeper sag.
Sensitivity: $\approx 79\%$
Specificity: $\approx 100\%$
Notes: Specificity reported in only one study; clinicians should be suspicious of this value.

PCL: Posterior Drawer Test

Positive Finding: Excessive posterior translation and a lack of end-feel.
Sensitivity: $\approx 90\%$
Specificity: $\approx 99\%$
Notes: Specificity reported in only one study; proceed with suspicion.

MCL: Valgus Stress Test (tested at $30^\circ$ flexion)

Positive Finding: Excessive medial gapping and/or comparable medial knee pain.
Sensitivity: Pain: $78\%$ , Laxity: $91\%$
Specificity: Pain: $67\%$ , Laxity: $49\%$
Notes: Lacks high-quality evidence; appears more sensitive than specific. Can be performed at $0^circ$ ; laxity at $0^circ$ may implicate the cruciate ligaments as well.

LCL: Varus Stress Test

Positive Finding: Excessive lateral gapping and/or comparable lateral knee pain.
Sensitivity: No quality research available.
Specificity: No quality research available.
Notes: Lacks high-quality diagnostic utility evidence. Similarly to the Valgus test, laxity at $0^circ$ suggests potential cruciate involvement.

Special Tests: Meniscus Integrity

McMurray Test

Positive Finding: Palpable or audible click, potentially with familiar symptoms.
Sensitivity: $\approx 45\%$
Specificity: $\approx 85\%$
Mechanism: External rotation tests medial meniscus; Internal rotation tests lateral meniscus. Varus/valgus moments may be added to increase compression.

Thessaly Test

Positive Finding: Familiar joint line pain and potential clicking, locking, or catching.
Sensitivity: $\approx 80\%$
Specificity: $\approx 57\%$
Procedure: Perform at $5^\circ$ and $20^\circ$ of flexion.
Notes: Values include recent research (Blyth et al. 2015, Goossens et al. 2015, Snoeker et al. 2015).

Apley Test

Positive Finding:
- Pain with Distraction: Indicates soft tissue sprain.
- Pain/Clicking with Compression: Indicates meniscus involvement.
Sensitivity: $\approx 31\%$
Specificity: $\approx 82\%$

Test Item Cluster (TIC) for Meniscus Integrity

According to Lowery 2006, there are five variables used to identify meniscus integrity:

Locking of the knee.
Joint Line Tenderness.
Positive McMurray’s Test.
Pain on Terminal Flexion.
Pain on Terminal Extension.

Diagnostic Probabilities:

All 5 Positive: Sensitivity $11\%$ , Specificity $99\%$
$> 4$ Positive: Sensitivity $17\%$ , Specificity $96\%$
$> 3$ Positive: Sensitivity $31\%$ , Specificity $90\%$