Knee Joint Examination: Observation, Palpation, Range of Motion, and Special Tests

How to examine a knee joint?

Examining a knee joint involves a systematic, multi-faceted approach, encompassing observation, palpation, assessment of range of motion and strength, and specific special tests to evaluate the integrity of ligaments, menisci, and other structures.

The Importance of a Systematic Knee Examination

A thorough and structured examination of the knee joint is paramount for accurately identifying the source of pain, dysfunction, or instability. Given the knee's complex role in weight-bearing, locomotion, and energy absorption, a methodical approach ensures that no critical components are overlooked. For fitness enthusiasts, personal trainers, and student kinesiologists, understanding this process enhances diagnostic reasoning, informs exercise prescription, and guides appropriate referral when necessary. A systematic examination allows for the comparison of findings, helps differentiate between various pathologies, and forms the basis for effective intervention strategies.

Understanding Basic Knee Anatomy (Brief Review)

Before examining the knee, a quick review of its fundamental structures is beneficial. The knee is primarily a hinge joint formed by the articulation of the femur (thigh bone), tibia (shin bone), and patella (kneecap). The fibula (lower leg bone) is also present laterally but does not directly articulate with the femur.

Key stabilizing structures include:

• Ligaments:
  • Cruciate Ligaments: Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL) control anterior/posterior stability.
  • Collateral Ligaments: Medial Collateral Ligament (MCL) and Lateral Collateral Ligament (LCL) control valgus/varus stability.
• Menisci: The medial and lateral menisci are C-shaped cartilaginous discs that act as shock absorbers and help distribute forces within the joint.
• Muscles: The quadriceps femoris group (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) extends the knee, while the hamstrings (biceps femoris, semitendinosus, semimembranosus) flex it. The gastrocnemius also assists in knee flexion.

The Step-by-Step Examination Process

A comprehensive knee examination follows a logical sequence to gather objective information. Always begin by obtaining informed consent and ensuring the individual is comfortable and properly exposed.

1. Observation (Inspection)

Initial observation begins the moment the individual enters the room and continues throughout the examination.

• Gait Analysis: Observe the individual's walking pattern. Look for limping, antalgic gait (pain-avoiding), or any asymmetry.
• Static Posture and Alignment:
  • Standing: Note any genu varum (bow-legged), genu valgum (knock-kneed), or genu recurvatum (hyperextension).
  • Patellar Position: Assess for patella alta (high-riding), patella baja (low-riding), or patellar squinting (inward rotation).
• Skin and Soft Tissues:
  • Swelling/Effusion: Look for generalized swelling, localized swelling (e.g., prepatellar bursitis), or a distended joint capsule.
  • Bruising/Discoloration: Indicative of trauma.
  • Redness/Warmth: Suggests inflammation or infection.
  • Scars: From previous surgeries.
  • Muscle Atrophy: Especially of the quadriceps (vastus medialis obliquus).
• Patellar Tracking: Observe how the patella moves during active flexion and extension.

2. Palpation

Palpation involves systematically feeling the structures around the knee for tenderness, warmth, and swelling.

• Temperature: Compare the temperature of the affected knee to the unaffected knee. Increased warmth suggests inflammation.
• Effusion:
  • Patellar Tap Test (Ballotable Patella): With the knee extended, press down on the patella. If it depresses and then bounces back, it indicates significant effusion.
  • Fluid Wave Test: With the knee extended, stroke upwards on the medial side of the knee to milk fluid into the suprapatellar pouch, then tap the lateral side while feeling for a fluid wave on the medial side.
• Tenderness: Systematically palpate key anatomical landmarks:
  • Joint Lines: Medial and lateral (for meniscal or collateral ligament pathology).
  • Patellar Borders: Superior, inferior, medial, lateral (for patellofemoral pain, tendinopathy).
  • Patellar Tendon: For patellar tendinopathy ("jumper's knee").
  • Quadriceps Tendon: For quadriceps tendinopathy.
  • Collateral Ligaments: MCL (medial aspect), LCL (lateral aspect, often near fibular head).
  • Pes Anserine Bursa: Medial aspect of the tibia below the joint line.
  • Popliteal Fossa: Posterior aspect (for Baker's cyst, neurovascular issues).
• Crepitus: Feel for grinding or clicking sensations during passive or active movement, which can indicate articular cartilage damage or meniscal issues.

3. Range of Motion (ROM)

Assess both active (patient-initiated) and passive (examiner-initiated) range of motion.

• Active ROM:
  • Flexion: Ask the individual to bend their knee as far as possible.
  • Extension: Ask them to straighten their knee as far as possible.
  • Rotation: Assess internal and external rotation, typically with the knee flexed to 90 degrees.
• Passive ROM: Gently move the joint through its full range, noting any pain, stiffness, or mechanical blocks. Assess the "end-feel" (e.g., soft, firm, hard, empty).
• Goniometry: For objective measurement and tracking progress, use a goniometer to quantify flexion and extension angles.

4. Strength Assessment

Evaluate the strength of the major muscle groups surrounding the knee.

• Manual Muscle Testing (MMT):
  • Knee Extension: Quadriceps (e.g., isometric contraction against resistance).
  • Knee Flexion: Hamstrings (e.g., isometric contraction against resistance).
  • Hip Abduction/Adduction: While not directly knee muscles, hip strength significantly influences knee stability.
• Functional Strength: If appropriate and pain-free, observe functional movements like single-leg squats, lunges, or step-ups.

5. Special Tests (Ligamentous and Meniscal Stability)

These tests are designed to stress specific structures to assess their integrity. Always compare findings to the unaffected knee.

• Anterior Cruciate Ligament (ACL):
  • Lachman Test: With the knee flexed to 20-30 degrees, stabilize the femur and apply an anterior force to the tibia. Excessive anterior translation with a soft or absent end-feel suggests an ACL injury.
  • Anterior Drawer Test: With the knee flexed to 90 degrees, sit on the foot to stabilize and pull the tibia anteriorly. Excessive translation indicates an ACL injury.
• Posterior Cruciate Ligament (PCL):
  • Posterior Drawer Test: Similar to the anterior drawer, but push the tibia posteriorly. Excessive posterior translation indicates a PCL injury.
  • Posterior Sag Sign: Observe for a posterior sag of the tibia relative to the femur when the knee is flexed to 90 degrees and supported.
• Medial Collateral Ligament (MCL):
  • Valgus Stress Test: Apply a valgus (outward) force to the knee. Perform at 0 degrees (tests MCL, PCL, ACL, posterior capsule) and 30 degrees of flexion (isolates MCL). Excessive gapping or pain indicates an MCL injury.
• Lateral Collateral Ligament (LCL):
  • Varus Stress Test: Apply a varus (inward) force to the knee. Perform at 0 degrees (tests LCL, PCL, ACL, posterior capsule) and 30 degrees of flexion (isolates LCL). Excessive gapping or pain indicates an LCL injury.
• Meniscal Integrity:
  • McMurray Test: With the knee fully flexed, internally and externally rotate the tibia while slowly extending the knee. A click, clunk, or pain suggests a meniscal tear.
  • Apley's Compression/Distraction Test: With the individual prone and knee flexed to 90 degrees, apply compression and rotate the tibia (for meniscal tears) vs. distraction and rotation (for ligamentous injuries).
• Patellofemoral Joint:
  • Patellar Grind Test (Clarke's Sign): Press down on the superior pole of the patella and ask the individual to contract their quadriceps. Pain or crepitus suggests patellofemoral pain syndrome.
  • Patellar Apprehension Test: Gently push the patella laterally. If the individual expresses apprehension or tries to resist, it suggests patellar instability.

6. Neurovascular Assessment

While often performed by medical professionals, a basic neurovascular check is important, especially after acute trauma.

• Sensation: Test light touch in the dermatomes supplied by nerves around the knee (e.g., saphenous, common fibular, tibial nerves).
• Motor Function: Assess ankle dorsiflexion/plantarflexion, toe extension/flexion.
• Pulses: Palpate the popliteal pulse (behind the knee) and dorsalis pedis pulse (on the top of the foot) to ensure adequate blood flow.

Interpreting Findings and Next Steps

No single test provides a definitive diagnosis. It is crucial to synthesize all findings from the observation, palpation, ROM, strength, and special tests, correlating them with the individual's history and symptoms.

• Correlation: Look for patterns. For example, pain on the medial joint line with a positive valgus stress test points to an MCL injury.
• Referral: If significant instability, unmanageable pain, inability to bear weight, severe swelling, suspected fracture, or neurovascular compromise is present, immediate referral to a medical doctor, orthopedist, or physical therapist is essential.
• Exercise Professionals: For fitness professionals, a thorough examination guides appropriate exercise modifications, rehabilitation strategies (post-medical clearance), and injury prevention programs. Understanding the specific structures involved allows for targeted and safe training.
• Imaging: X-rays are useful for bony pathology, while MRI is the gold standard for soft tissue injuries (ligaments, menisci, cartilage). These are typically ordered by a physician.

Important Considerations and Disclaimer

This guide is intended for educational purposes for knowledgeable individuals such as fitness enthusiasts, personal trainers, and student kinesiologists. It provides a framework for understanding how a knee joint can be examined.

This information is NOT a substitute for professional medical diagnosis, treatment, or advice. Always consult with a qualified healthcare professional (e.g., physician, physical therapist, orthopedist) for any health concerns or before making any decisions related to your health or treatment.

When performing any assessment:

• Prioritize Safety: Always ensure the individual's safety and comfort. Stop if pain is excessive.
• Informed Consent: Always obtain verbal consent before beginning any physical examination.
• Comparison: Always compare findings to the unaffected limb.
• Limitations: Recognize the limitations of your scope of practice.