The Knee

Tibiofemoral Joint:

Joint Structure: Bicondylar Hinge Joint

Joint Function

• Biaxial movement

• 2 degrees of freedom (some argue it's 1 degree)

• Allows:

  • Flexion/Extension

  • Medial/Lateral Rotation (only when knee is flexed)

Articulations

• Femur: Medial & lateral femoral condyles

• Tibia: Tibial plateau

Cartilage

• Menisci (Medial & Lateral):

  • C-shaped fibrocartilage

  • Acts as a shock absorber

  • Improves joint stability

Movements

• Flexion (Bending): 0°–135°

• Extension (Straightening): 0°

• Medial & Lateral Rotation: Only occurs when the knee is flexed

Primary Muscles Involved

Extension: Quadriceps (Rectus Femoris, Vastus Medialis, Vastus Lateralis, Vastus Intermedius)

Flexion: Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus), Gastrocnemius, Sartorius, Gracilis, Popliteus

Ligaments (Joint Stability)

• Anterior Cruciate Ligament (ACL): Prevents anterior displacement of tibia

• Posterior Cruciate Ligament (PCL): Prevents posterior displacement of tibia

• Medial Collateral Ligament (MCL): Prevents valgus (inward) stress

• Lateral Collateral Ligament (LCL): Prevents varus (outward) stress

Synovial Fluid & Joint Capsule: Reduces friction, Nourishes cartilage, Allows smooth movement

Weight-Bearing Role: Supports body weight, Absorbs impact during walking, running, and jumping

Blood Supply: Genicular arteries (branches of the popliteal artery)

Nerve Supply: Femoral nerve (L2-L4): Quadriceps (extension), Sciatic nerve (L5-S2): Hamstrings (flexion), Tibial nerve (L4-S3): Popliteus, Gastrocnemius, Plantaris

 1. Medial & Lateral Femoral Condyles

How to Palpate:

• Position: Have the patient sit with their knee flexed to 90°.

• Procedure:

  • Place your fingers on both sides of the knee joint.

  • The medial and lateral femoral condyles are the rounded prominences above the tibiofemoral joint.

  • Move superiorly to feel the transition into the femoral shaft.

• Confirm:

  • Have the patient extend and flex the knee; the condyles should remain relatively stable.

5. Patella

How to Palpate:

• Position: Patient sitting with the knee extended and relaxed.

• Procedure:

  • The patella is a freely movable bone within the quadriceps tendon.

  • Place fingers on the superior, inferior, medial, and lateral aspects to assess movement.

• Confirm:

  • The patella moves freely when the quadriceps are relaxed but tightens when they contract.

7. Patellar Ligament

How to Palpate:

• Position: Patient sitting with knee extended and relaxed.

• Procedure:

  • Locate the apex of the patella and move downward towards the tibial tuberosity.

  • The thick, strong band connecting them is the patellar ligament.

• Confirm:

  • Ask the patient to contract their quadriceps—the ligament will tighten under your fingers.

6. Patella: Base, Apex, Medial & Lateral Borders

How to Palpate:

• Base (Superior Border):

  • Found at the top of the patella; move superiorly to feel the attachment of the quadriceps tendon.

• Apex (Inferior Tip):

  • The pointed lower end of the patella; where the patellar ligament attaches.

• Medial & Lateral Borders:

  • Slide fingers along the sides of the patella.

  • Medial border is near the vastus medialis, and lateral border near the vastus lateralis.

• Confirm:

  • Move the patella side-to-side gently while the knee is relaxed to assess mobility.

9. Head of the Fibula

How to Palpate:

• Position: Patient sitting with knee flexed to 90°.

• Procedure:

  • Locate the lateral tibial condyle, then move posterolaterally.

  • The rounded prominence just below the lateral knee joint is the fibular head.

• Confirm:

  • Ask the patient to dorsiflex the foot—the biceps femoris tendon attaches here and can be felt contracting.

Tibiofemoral Joint and Tibia – Anatomical Overview

• The distal femur articulates with the proximal tibia to form the tibiofemoral joint.

• Each femoral condyle has a separate articulation with the tibial plateau.

• The supracondylar ridges and adductor tubercle serve as muscular attachment points.

• The tibial plateau is flattened, with the intercondylar eminence positioned centrally.

• Menisci are required to increase depth and improve joint congruency for the femoral condyles.

• The lateral condyle features an articular facet for the head of the fibula.

• The anteroproximal tibial tuberosity serves as the attachment point for the patellar ligament (quadriceps tendon).

• The tibial shaft is triangular in cross-section, with a distinct anterior border.

• Distally, the medial malleolus extends downward, contributing to ankle stability.

• The inferior surface of the tibia is smooth, allowing articulation with the talus.

• The tibia is the primary weight-bearing bone, transmitting forces from the medial and lateral femoral condyles to the foot.

4. Intercondylar Eminence

How to Palpate:

• Position: Patient in supine or sitting position with knee slightly flexed.

• Procedure:

  • The intercondylar eminence is located between the tibial plateaus.

  • It is difficult to palpate externally but can sometimes be felt as a slight elevation when pushing posteriorly at the anterior tibial plateau.

• Confirm:

  • Difficult to palpate directly but can be identified with slight tibial movement in flexion.

3. Tibial Plateau

How to Palpate:

• Position: Patient sitting with knee flexed to 90°.

• Procedure:

  • Place thumbs on either side of the patellar tendon.

  • Press inferiorly and slightly posteriorly to locate the flat surface beneath the condyles.

  • The tibial plateau is where the medial and lateral menisci sit.

• Confirm:

  • Move fingers medially and laterally to feel the plateau edges.

  • It becomes more prominent when the knee is fully extended.

8. Adductor Tubercle

How to Palpate:

• Position: Patient sitting with the knee flexed to 90° or supine with slight hip abduction.

• Procedure:

  • Locate the medial femoral condyle.

  • Move superiorly along the medial supracondylar ridge.

  • The adductor tubercle is a small bony prominence where the adductor magnus tendon inserts.

• Confirm:

  • Press firmly—it may be tender due to its muscular attachment.

Patellofemoral Joint & Importance of the Patella

Patellofemoral Joint Overview

• The patellofemoral joint is the articulation between the patella (kneecap) and the femoral trochlear groove (on the distal femur).

• It is a gliding synovial joint, where the patella moves superiorly and inferiorly along the trochlear groove during knee flexion and extension.

• The joint is stabilized by the quadriceps muscle, patellar ligament, medial and lateral retinacula, and surrounding soft tissues.

Patellar Tracking

• During knee flexion, the patella moves inferiorly and engages deeper in the femoral groove.

• During knee extension, it moves superiorly, reducing contact with the femur.

• Proper tracking of the patella is crucial for smooth motion and knee stability.

Tibio-Fibula Joint

•         Joint Structure: 

•         Synovial plane joint

•         Joint Function:

•         Not anatomically part of the “knee joint”

•         Inferior/superior/anterior/posterior glides – related to ankle function

•         Articulations:

•         Fibula head

•         Lateral tibial condyle 

Proximal Tibio-Fibular Joint: Located near the knee, where the head of the fibula articulates with the tibia. It is a synovial joint, allowing for some gliding and rotational movements. However, it does not play a significant role in weight-bearing.

Distal Tibio-Fibular Joint: Found near the ankle, where the fibula and tibia are connected via a syndesmosis (a fibrous joint). This connection provides stability to the ankle joint, particularly during weight-bearing activities, and permits minimal movement.

2. Medial & Lateral Supracondylar Ridges

How to Palpate:

• Position: Patient in a relaxed sitting or supine position with the leg slightly bent.

• Procedure:

  • From the femoral condyles, move upward along the femur.

  • Feel the bony ridges extending superiorly and posteriorly on both the medial and lateral sides.

• Confirm:

  • These ridges are more prominent in thinner individuals.

  • The medial supracondylar ridge leads toward the adductor tubercle.

Importance of the Patella

1.          Increases Quadriceps Efficiency

o   The patella acts as a fulcrum, increasing the mechanical advantage of the quadriceps by lengthening the moment arm.

o   This enhances knee extension force, reducing effort required for movement.

2.          Protects the Knee Joint

o   The patella shields the anterior knee joint from direct trauma.

o   It distributes forces applied to the knee, reducing excessive stress on the femoral condyles.

3.          Reduces Friction

o   The smooth articular cartilage on the posterior patella reduces friction between the quadriceps tendon and the femur.

4.          Enhances Stability

o   The patella centralizes quadriceps pull, preventing lateral displacement and promoting knee alignment.

o   Medial and lateral patellar stabilizers prevent excessive side-to-side movement.

5.          Force Transmission

o   The patellar ligament connects the patella to the tibial tuberosity, efficiently transmitting forces from the quadriceps to enable knee extension.

Locking Mechanism of the Knee:

How it works: When the knee extends, the tibia rotates externally relative to the femur (or the femur rotates internally relative to the tibia). This action causes the tibia to "lock" into place, enhancing stability and minimizing the need for muscular activation to maintain the extended position.

 Biomechanical Implication: During the last few degrees of extension, the lateral femoral condyle (on the femur) is larger than the medial condyle. As the knee extends, this causes a slight external rotation of the tibia (in relation to the femur), which locks the knee into full extension. This rotation stabilizes the joint during weight-bearing activities, reducing the energy required to maintain standing.

1. Final 20° of Knee Extension and the Screw-Home Mechanism

• Knee Extension: As the knee moves toward full extension, the final 20° is crucial for locking the knee into place. This "locking" mechanism is known as the Screw-Home Mechanism, which serves to stabilize the knee joint during standing and reduces the need for muscular effort to maintain that position.

• Convex Femoral Condyles: The femoral condyles are convex in shape, and during extension, they roll and slide over the tibial plateau. In the final 20° of extension, the convex femoral condyles rotate internally (medially) over the tibia in closed-chain movements (where the foot is fixed, like standing).

• External Rotation of Tibia: In open-chain movements (where the foot is not fixed, like when sitting and extending the knee), the tibia rotates externally in relation to the femur during the last 20° of extension. This rotation creates the locking mechanism in both open and closed chains.

2. Ligament Tightening and Closed-Pack Position

• As the knee approaches full extension, the ligaments around the knee (such as the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and collateral ligaments) become taut. This tension in the ligaments contributes to the knee being in its closed-pack position — a stable configuration where the joint surfaces fit closely together and provide maximum stability.

• The closed-pack position is the position where the knee is fully extended, and the ligaments, particularly those that cross the knee joint (ACL and PCL), are at their tightest. This tightness increases the joint's stability and prevents excessive movement, particularly when weight-bearing.

3. Unlocking the Knee: The Role of the Popliteus Muscle

• The knee is "unlocked" from this fully extended, stable position by the popliteus muscle. The popliteus muscle plays a crucial role in the transition from full extension to slight flexion.

• In open-chain movements, the popliteus muscle internally rotates the tibia, thus "unwinding" the external rotation that occurred during the locking phase of extension.

• In closed-chain movements, the popliteus externally rotates the femur relative to the tibia, which also helps to "unlock" the knee. Essentially, this muscle breaks the rotational lock that the screw-home mechanism created, allowing the knee to flex.

Q Angle (Quadriceps Angle)

The Q angle is the angle formed between two lines:

1.          One line from the ASIS (Anterior Superior Iliac Spine) to the center of the patella.

2.          The second line from the center of the patella to the tibial tuberosity (a bony prominence on the tibia just below the knee).

This angle reflects the alignment of the quadriceps muscle, the patella, and the tibial shaft. In other words, it indicates the angle at which the quadriceps force is applied to the patella relative to the tibia.

Normal Q Angle:

• For women: The normal Q angle is typically 15-20 degrees.

• For men: The normal Q angle is generally 10-15 degrees.

Factors that Affect Q Angle:

• Pelvic width: Wider hips can increase the Q angle, which is more common in women.

• Femoral anteversion (excessive inward twisting of the femur) or tibial torsion (abnormal rotation of the tibia).

• Patella alignment: If the patella is not aligned properly (e.g., in patella alta or patella baja), the Q angle may be altered.

• Muscle imbalances: Weakness or tightness in the quadriceps or hamstrings can impact patella tracking and alter the Q angle.

Clinical Implications of Q Angle:

1.          Patellofemoral Pain Syndrome (PFPS) and Patellar Malalignment:

o   Increased Q Angle: A larger Q angle can lead to abnormal patellar tracking, where the patella does not move smoothly within the femoral groove, resulting in patellofemoral pain syndrome (also called runner's knee). This is often seen in individuals with wider hips (more common in females) and can contribute to discomfort, pain, or inflammation around the kneecap.

o   Lateral Tracking of the Patella: A higher Q angle can also contribute to lateral displacement of the patella (where the patella moves towards the outer side of the knee). This can cause irritation, instability, or damage to the cartilage on the femoral condyle, leading to pain and wear and tear on the knee joint.

2.          Anterior Cruciate Ligament (ACL) Injury Risk:

o   A higher Q angle is sometimes associated with an increased risk of ACL injuries. This is because the altered alignment of the knee joint (often related to a larger Q angle) can place more strain on the ACL, especially during activities that involve sudden stops, pivots, or changes in direction (like sports such as soccer, basketball, or skiing).

o   The misalignment can also affect the mechanical efficiency of the knee joint during dynamic movements, leading to instability or higher stresses on the ACL.

3.          Genu Valgum (Knock Knees):

o   A larger Q angle can be associated with genu valgum, or knock knees, where the knees angle inward and touch while the feet are apart. This condition places additional stress on the medial (inner) structures of the knee, leading to possible pain and dysfunction over time.

4.          Genu Varum (Bowlegs): In genu varum, the knees angle outward, and the tibia deviates laterally from the femur. As the knees are positioned farther apart, the line from the ASIS to the patella becomes more angled. This can lead to an increase in the Q angle.

Knee Structures- Ligaments:

• Medial Collateral Ligament (MCL):

  • Origin: Medial femoral epicondyle

  • Insertion: Medial tibia

  • Function: Stabilizes the knee medially, preventing excessive valgus (inward) motion & restricts Hyperextension

• Lateral (Fibular) Collateral Ligament (LCL):

  • Origin: Lateral femoral epicondyle

  • Insertion: Head of the fibula

  • Function: Stabilizes the knee laterally, preventing excessive varus (outward) motion & restrict hyperextension

• Anterior Cruciate Ligament (ACL):

  • Origin: Anterior tibia, just below the plateau

  • Insertion: Posterior femoral condyle (lateral side)

  • Function: Prevents anterior translation of the tibia relative to the femur and limits knee hyperextension.

  • Posterolateral band is tight in extension, Anteromedial band is lax in extension

• Posterior Cruciate Ligament (PCL):

  • Origin: Posterior tibia

  • Insertion: Anterior femoral condyle

  • Function: Prevents posterior translation of the tibia relative to the femur (open chain) & anterior translation of femur on tibia (closed chain)

  • Taut in EOR flexion.

• Oblique Popliteal Ligament (OPL):

  • Origin: Tendon of the semimembranosus muscle (posteromedial knee)

  • Insertion: Lateral femoral condyle

  • Function: Reinforces the posterior knee capsule and helps prevent hyperextension.

• Arcuate popliteal Ligament:

  • Origin: Fibular head

  • Insertion: Lateral femoral condyle

  • Function: Provides additional stability to the posterior knee and assists the popliteus in knee rotation.

Knee Structures- Bursae:

•         Important lubricated fluid-filled thin sac located between bone and surrounding soft tissue, bones and tendons, and/or muscles around joints.

•         Baker’s Cyst is also called a popliteal cyst as it relates to the posterior aspect of the knee. It is a fluid-filled swelling that can cause pain in the knee and calf, a build-up of fluid around the knee and occasional locking or clicking in the knee joint.

•         It is a benign swelling of the semimembranous muscle or of the posterior synovial bursa. It is named after William Morrant Baker being the surgeon who first described it.

•         Housemaid’s Knee = pre-patella bursa

•         Housemaid's knee is ‘prepatellar bursitis’. It is caused by inflammation of the bursa inferior to the patella on the anterior aspect of the knee. It is most commonly caused by acute or chronic, repetitive, trauma to the knee.

 Prepatellar Bursae:

• Located in front of the patella; protects the patella from friction against the skin.

Infrapatellar Bursae:

• Located below the patella; cushions the patellar tendon.

 Suprapatellar Bursae:

• Located above the patella; allows the quadriceps tendon to glide smoothly over the femur.

Pes Anserine Bursae:

• Located between the tibia and the tendons of the sartorius, gracilis, and semitendinosus muscles; reduces friction where the tendons insert on the tibia.

Knee Structures- Menisci:

•         C-Shaped fibrocartilaginous wedge, Poor vascularity, Common site of injury

Functions:

Increase joint congruency

Spread load bearing

shock absorbers

lubrication

to participate in the locking mechanism

Peripheral Borders: Thick, convex, and vascularized.

Greater Vascularity in Youth:

• In children (<11 years), menisci have a rich blood supply.

• This results in enhanced healing and a lower tendency for injury.

Mature Menisci (After 11 Years):

• Blood supply decreases.

• Only the outer 20% and the horns remain vascularized.

• The inner portions rely on nutrition from synovial fluid.

Nerve Supply:

• The outer third contains some non-myelinated nerve fibers, though their function remains unclear.

• Limited innervation contributes to reduced pain perception in inner meniscus injuries.

Medial Meniscus:

• Shape: C-shaped

• Function: Acts as a shock absorber, improves joint stability, and helps distribute weight across the knee.

 Lateral Meniscus:

• Shape: O-shaped

• Function: Similar to the medial meniscus, it absorbs shock and helps with stability. The lateral meniscus is more mobile than the medial one.

Knee Injuries:

Triad (Unhappy Triad): O’Donohue’s Triad

• Injury: A common knee injury involving the simultaneous rupture of:

  • Medial Collateral Ligament (MCL)

  • Anterior Cruciate Ligament (ACL)

  • Medial Meniscus.

• Cause: Often occurs from a traumatic blow to the knee, such as during contact sports.

How to Test:

• Lachman & Pivot-Shift → Best for ACL tear

• Valgus Stress Test → Best for MCL tear

• McMurray & Apley’s → Best for Medial Meniscus tear

A combination of positive tests for ACL, MCL, and medial meniscus confirms the Unhappy Triad diagnosis. MRI is often used to confirm findings.

Pes Anserine: Goose Foot

 Muscle Group: Refers to the tendons of the sartorius, gracilis, and semitendinosus muscles, which insert together on the medial tibia.

  Function:

• Provides medial stability to the knee and assists with knee flexion and internal rotation.

Muscle Support and Other Structures:

• Quadriceps Tendon and Patella:

  • Anteriorly, the quadriceps tendon blends with the patella to form a complex of structures that extend the knee.

• Medial Structures:

  • The medial capsule blends with the MCL and the medial meniscus, helping to stabilize the medial aspect of the knee.

• Posteromedial Support:

  • The semimembranosus tendon and oblique popliteal ligament provide posterior-medial support to the knee joint, preventing excessive extension and internal rotation.

• Lateral Structures:

  • Laterally, the knee is supported by the iliotibial tract, which contributes to knee stability and lateral support during walking and running.

• Posterolateral Support:

  • The popliteus muscle helps stabilize the posterior-lateral aspect of the knee, assisting in unlocking the knee during flexion.

Physiological Movements (Osteokinematics)

These are the active movements that occur at the knee joint:

✅ Flexion & Extension

• Flexion: 0° to ~135° (Hamstrings, gastrocnemius, popliteus)

• Extension: 135° to 0° (Quadriceps)

• Occurs in the sagittal plane

✅ Internal & External Rotation (only when knee is flexed)

• Internal Rotation: ~10–15°

• External Rotation: ~30–40°

• Occurs in the transverse plane

• Needed for the "Screw Home Mechanism" (locks/unlocks knee for stability)

Accessory Movements (Arthrokinematics)

These are passive movements that occur within the joint:

✅ Anterior & Posterior Glide

• Anterior glide occurs with knee extension

• Posterior glide occurs with knee flexion

✅ Medial & Lateral Glide

• Controlled by ligamentous tension (e.g., MCL/LCL)

• Limited in normal movement but increased in instability

✅ Screw Home Mechanism (Locking Mechanism)

• Final 20° of extension:

  • Closed-chain (weight-bearing): Femur internally rotates on tibia.

  • Open-chain (non-weight-bearing): Tibia externally rotates on femur.

• Ligaments tighten, creating a closed-packed stable position.

• Popliteus muscle "unlocks" the knee by reversing the rotation.

Quadriceps Group (Knee Extension)

These muscles are located anteriorly and work to extend the knee.

Quadriceps weakness → Knee instability, difficulty standing.

A. Rectus Femoris

• Origin: Anterior Inferior Iliac Spine (AIIS)

• Insertion: Tibial tuberosity (via patellar tendon)

• Palpation:

  • Patient seated with knee extended.

  • Place hand on the middle of the thigh and ask the patient to extend the knee.

  • A firm contraction can be felt in the center of the thigh.

B. Vastus Lateralis

• Origin: Greater trochanter & lateral linea aspera of femur

• Insertion: Tibial tuberosity (via patellar tendon)

• Palpation:

  • Place hand on the outer (lateral) thigh.

  • Ask the patient to extend the knee against resistance.

  • A firm contraction is felt on the lateral side.

C. Vastus Medialis

• Origin: Medial linea aspera of femur

• Insertion: Tibial tuberosity (via patellar tendon)

• Palpation:

  • Place hand above and medial to the knee (VMO – vastus medialis oblique).

  • Ask the patient to extend the knee, especially the last 15° of movement.

  • The teardrop-shaped muscle contraction can be seen and felt.

D. Vastus Intermedius (Deep Muscle)

• Origin: Anterior & lateral shaft of the femur

• Insertion: Tibial tuberosity (via patellar tendon)

• Palpation:

  • Not directly palpable as it lies beneath the rectus femoris.

Other Key Muscles of the Knee

A. Popliteus ("Unlocks" the Knee)

• Origin: Lateral condyle of the femur

• Insertion: Posterior tibia

• Function: Internally rotates tibia to "unlock" the knee.

• Palpation: Difficult to palpate due to deep location, but pressure in the posterior knee while resisting internal rotation may activate it.

B. Gastrocnemius (Calf Muscle, Assists with Knee Flexion)

• Origin:

  • Medial head: Medial condyle of femur

  • Lateral head: Lateral condyle of femur

• Insertion: Achilles tendon → Calcaneus

• Palpation: Ask the patient to stand on their toes, The bulky calf muscle will be visible and palpable.

C. Sartorius (Longest Muscle in the Body)

• Origin: Anterior Superior Iliac Spine (ASIS)

• Insertion: Pes anserinus (medial tibia)

• Function: Assists knee flexion and internal rotation

• Palpation: Ask the patient to flex, abduct, and externally rotate the hip (like crossing the leg over the knee), Feel for a thin muscle running from the ASIS toward the medial knee.

D. Gracilis (Medial Thigh Muscle)

• Origin: Pubis

• Insertion: Pes anserinus (medial tibia)

• Function: Assists knee flexion and adduction

• Palpation: Feel for the inner thigh muscle running toward the knee, activated by resisted adduction.

E. Tensor Fasciae Latae (TFL) & Iliotibial (IT) Band

• Origin: Iliac crest & ASIS

• Insertion: Lateral condyle of tibia (Gerdy's tubercle) via IT band

• Function: Assists in knee stabilization and extension

• Palpation: ask the patient to flex and internally rotate the hip, The TFL muscle can be felt just lateral to the hip.

Hamstrings Group (Knee Flexion)

Located posteriorly, responsible for knee flexion and hip extension.

Hamstring tightness → Reduced knee extension, increased ACL injury risk.

A. Biceps Femoris (Lateral Hamstring)

• Origin:

  • Long head: Ischial tuberosity

  • Short head: Linea aspera of femur

• Insertion: Head of the fibula

• Palpation:

  • Ask the patient to flex the knee.

  • Palpate the lateral tendon on the outer back of the knee.

B. Semitendinosus (Medial Hamstring)

• Origin: Ischial tuberosity

• Insertion: Pes anserinus (medial tibia)

• Palpation:

  • Ask the patient to flex the knee.

  • Feel the medial tendon, which is more prominent than semimembranosus.

C. Semimembranosus (Medial Hamstring, Deeper)

• Origin: Ischial tuberosity

• Insertion: Medial condyle of the tibia

• Palpation:

  • Lies deep to semitendinosus.

  • Palpate just medial and deep to the semitendinosus tendon.

Assessment of the Knee: LOOK

•         Bursae: pre-patella, infrapatella (housemaid vs. clergyman’s)

•         Scars

•         Lesions

•         Signs of trauma / previous surgery

•         Swelling vs. effusion

•         Redness

•         Muscle bulk symmetry

•         Internal femoral rotation; due to insufficient gluteal function is a common finding with patients with PFP and can cause squinting of the patella and increased Q-angle.

•         Enlarged tibial tuberosity: An enlarged tibial tuberosity is often associated with conditions affecting the patellar tendon attachment at the tibial tuberosity, i.e Osgood Schlatter’s disease, fracture, patellar tendinopathy

•         Medial lateral tibial torsion

•         Foot pronation

Special Tests: Joint Effusion

abnormal accumulation of fluid within a joint capsule or body cavity

Patella tap

Purpose:  To assess for presence of fluid in the knee

Technique: Patient lying supine, clinician adds pressure across the suprapatellar pouch (with one hand). With the other hand the clinician applies a light downward force (tap) to the patella which in the presence of an effusion will feel as if the patella is “floating”

Interpretation: The test is positive for effusion, if the patellar bounces off the underlying bone

Sweep test

Purpose:  To assess for presence of fluid in the knee

Technique: Palm of one hand sweeps fluid proximally up the medial side of the knee into the suprapatellar pouch. The other hand is then used to sweep distally down the lateral side. 

Interpretation: In the presence of effusion, a small bulge of fluid will appear on the medial side of the knee. 

Special Tests: Active Range of Motion (AROM) of the Knee

✅ Purpose: Assesses the patient's ability to move the knee independently, Muscle strength and control
✅ Movements Tested:

• Flexion (bending the knee)

• Extension (straightening the knee)

🔹 How to Perform AROM:

1.          Patient Position:

o   Seated on the edge of a table OR lying supine.

2.          Knee Flexion:

o   Ask the patient to bend their knee as far as possible.

o   Normal ROM: 0–135°

3.          Knee Extension:

o   Ask the patient to straighten the knee completely.

o   Normal ROM: 0° (some may have slight hyperextension up to -5°)

✅ Observations:

• Pain or stiffness? Pain indicates Muscle/tendon issues

• Restricted movement?

• Any abnormal compensations?

🔹 Reduced AROM & PROM: Joint stiffness, arthritis, meniscus injury.
🔹 Pain in AROM but not PROM: Muscle or tendon issue (e.g., quadriceps strain).
🔹 Pain in both AROM & PROM: Joint pathology (e.g., osteoarthritis, ligament tear).

Passive Range of Motion (PROM) of the Knee

✅ Purpose: Assesses joint flexibility, end feel, and restrictions without patient muscle effort.

🔹 How to Perform PROM:

1.          Patient Position: Lying supine and relaxed.

2.          Knee Flexion:

o   Hold the patient’s ankle and slowly bend the knee toward their buttocks.

o   Stop when resistance or discomfort occurs.

o   Normal ROM: 0–135°

3.          Knee Extension:

o   Hold the leg at the ankle and gently straighten the knee.

o   Normal ROM: 0° to slight hyperextension (-5° to -10° in some individuals).

✅ Observations:

• Compare both knees for symmetry.

• Look for pain, stiffness, or muscle guarding, Pain indicates Joint/capsular/ligament issues

• End Feel:

  • Flexion: Soft (due to muscle bulk).

  • Extension: Firm (due to ligaments & capsule).

🔹 Reduced AROM & PROM: Joint stiffness, arthritis, meniscus injury.
🔹 Pain in AROM but not PROM: Muscle or tendon issue (e.g., quadriceps strain).
🔹 Pain in both AROM & PROM: Joint pathology (e.g., osteoarthritis, ligament tear).

Special Tests: Joint Integrity

Anterior Drawer test

Anterior Cruciate Ligament

Purpose: To assess the integrity of the ACL

Technique: In lying, flex the knee to 90° without tibial rotation. Place both hands on the posterior proximal tibia and pull the upper part of the leg forwards.

Interpretation: The test is positive if the tibia moves anteriorly without an abrupt stop, suggesting a rupture.

Posterior Drawer test

Posterior Cruciate Ligament

Purpose:  To assess the integrity of the PCL

Technique: In lying with 90° of knee flexion, posterior sagging of the tibia is observed on the affected side.

Interpretation: The test is positive if the tibia moves posteriorly without an abrupt stop, suggesting a rupture

Dial Test

PLC: Posterior Lateral Corner

Purpose:  To detect PLC or PLC + PCL ruptures.

Technique: Patient is in prone, passively flex the patient’s knees to 30⁰. Then, externally rotate the feet, looking for asymmetry. Repeat at 90 degrees knee flexion.

Interpretation:  The test is positive if there is an increase in ER >10 degrees (at 30 degrees knee flexion). At 90 degrees, in there is an increase in laxity, there is a possible PLC and PCL.

Lachman’s Test

Purpose: Used to assess Anterior Cruciate Ligament (ACL) integrity, More sensitive than the Anterior Drawer Test, especially for acute ACL tears.

Technique: The patient lies supine, The knee is flexed to 20-30° (not 90°, like in the Anterior Drawer Test), One hand stabilizes the distal femur (above the knee), The other hand grasps the proximal tibia (just below the knee).

Apply a quick anterior translation (pulling forward) on the tibia while stabilizing the femur.

Interpretation: Increased anterior translation of the tibia compared to the uninjured knee, Soft or absent end-feel (normally, the ACL should stop tibial movement firmly), May indicate a partial or complete ACL tear.

Special Tests: Joint Integrity

Varus stress test- Varus (Bowlegs): Imagine legs forming a rounded "O" shape.

LCL: Lateral Collateral Ligament

Purpose:  To assess the integrity of the LCL

Technique: Place the knee into 20’- 30’ degrees of flexion. Stabilise around the knee whilst being able to palpate the LCL and apply an adducting (varus) strain for the LCL. Repeat the above at 0 degrees of flexion.

Interpretation: The test is positive if there is excessive gapping on the lateral side and reproduction of pain.

Valgus stress test- Valgus (Knock-Knees): Imagine knees "knocking" together like a letter "L" shape.

MCL: Medial Collateral Ligament

Purpose:  To assess the integrity of the MCL

Technique: Place the knee into 20’- 30’ degrees of flexion. Stabilise around the knee whilst being able to palpate the MCL and apply an abducting (valgus) strain for the MCL. Repeat the above at 0 degrees of flexion.

Interpretation: The test is positive if there is excessive gapping on the medial side and reproduction of pain.

Special Tests: Meniscus Tests

Thessaly test

Purpose:  To detect meniscus lesions

Technique: Stand on one leg, with it flexed to 20 degrees, holding onto the therapists arms for support. Then ask the patient to twist their body side to side, effectively rotating the tibia. Repeat three times

Interpretation: The test is positive if there are reports of pain around the joint line or hesitation to perform the movement.

McMurray test

Purpose:  To detect meniscus lesions 

Technique: Supine lying position with the tested knee fully flexed by the therapist. Then, rotate the tibia media and bring the knee into extension. This is then repeated a few times with different degrees of knee flexion to test the posterior compartment of the LATERAL meniscus. For the medial meniscus, bring the foot into full flexion and lateral rotate the tibia.

Interpretation: The test is positive if there is clicking, locking or pain in the knee.

Joint line tenderness

Purpose:  To detect meniscus lesions. Often used as an adjunct with other tests. Combined with McMurray = likely tear

Technique: Patient is in supine, with knee bent 90⁰ fix the tested leg, and flex the patient’s knee to 90 degrees and . Flexion facilitates palpation of the anterior meniscus.

Interpretation:  The test is positive if the patient’s familiar pain is reproduced. Combined with McMurray = likely tear.

Steadman Criteria – Meniscal injury = 92% positively predicted

•         History of catching or locking

•         Pain with forced hyperextension

•         Pain with maximum flexion

•         Pain or audible click with McMurray’s

•         Joint Line Tenderness

Special Tests: Anterior Knee Pain

McConnel’s Test

Purpose:  To test for Patella femoral pain syndrome (PFPS).

Technique: Ask the patient to initiate and maintain isometric knee flexion and varying degrees. Start at 120 degrees flexion, then 90 degrees, 60 degrees, 30 degrees and finally full extension. Where there is pain, then apply a medial patella glide

Interpretation:  The test is positive for PFPS if the pain is reduced by the medial patella glide.

Clark’s sign

Purpose:  To test for Patella femoral pain syndrome (PFPS).

Technique: Patient is lying in supine. Place the web space of the thumb on the superior boarder of the patella. The ask the patient to contract their quads and place downward and inferior pressure on the patella.

Interpretation:  The test is positive for PFPS if the pain is produced with movement of the patella or apprehension to do the test.

PNF in Knee Rehabilitation

What is PNF in Knee Rehab?

• Proprioceptive Neuromuscular Facilitation (PNF) is used in knee rehabilitation to enhance flexibility, strength, and neuromuscular control.

• It helps restore function and promotes range of motion (ROM), which is essential for recovering from injuries like ACL tears, meniscus injuries, or knee surgeries.

How PNF Helps in Knee Rehab:

• PNF techniques (e.g., Contract-Relax (CR), Hold-Relax (HR)) can assist in improving joint mobility, reducing muscle stiffness, and restoring normal muscle function around the knee.

• It also works on proprioception, which is vital for joint stability, balance, and preventing future knee injuries.

Relaxation / Lengthening Techniques for Knee Rehabilitation

Purpose of Relaxation Techniques:

• Help reduce muscle tension and improve flexibility around the knee joint.

• Lengthening techniques focus on improving ROM and reducing tightness in the quadriceps, hamstrings, and calf muscles, which are crucial for optimal knee function.

Techniques for Knee Rehab:

• Static Stretching: Hold stretches for muscles surrounding the knee, like the quadriceps (front thigh), hamstrings (back thigh), calf, and hip flexors.

• Dynamic Stretching: For warming up and increasing flexibility, dynamic stretching improves joint mobility.

• PNF Stretching: Techniques like Contract-Relax (CR) and Hold-Relax (HR) target the quadriceps, hamstrings, and calf to improve flexibility and muscle activation.

Autogenic Inhibition in Knee Rehab

What is Autogenic Inhibition?

• Autogenic inhibition is a process where the Golgi Tendon Organ (GTO) detects excessive tension in a muscle and sends a signal to relax it.

• In knee rehab, this process is used to help lengthen and relax tight muscles, especially the quadriceps or hamstrings, after active contraction.

Example in Knee Rehab:

• PNF Contract-Relax (CR):

  • For quadriceps: In this technique, the quadriceps is contracted isometrically (without moving) for several seconds. After this contraction, the muscle relaxes, allowing for a deeper stretch. This helps lengthen the quadriceps and improve flexibility around the knee.

Benefits for Knee Rehab:

• Increases flexibility in the quadriceps, hamstrings, and calves.

• Reduces muscle guarding and muscle tightness, common after knee surgeries or injuries.

Reciprocal Inhibition in Knee Rehab

What is Reciprocal Inhibition?

• Reciprocal inhibition occurs when the contraction of one muscle leads to the relaxation of its antagonist (opposing muscle). For example, when the quadriceps contracts, the hamstrings relax.

• This mechanism is used in knee rehab to improve muscle balance and coordination.

Example in Knee Rehab:

• Contract-Relax-Antagonist-Contract (CRAC):

  • For hamstrings: The patient contracts the hamstrings (agonist) and then relaxes them. After the relaxation phase, the quadriceps (antagonist) are actively contracted, promoting the relaxation and lengthening of the hamstrings. This enhances flexibility and muscle activation around the knee joint.

Benefits for Knee Rehab:

• Improves the neuromuscular relationship between agonists and antagonists (e.g., quadriceps and hamstrings).

• Promotes joint stability and muscle coordination.

• Essential for post-surgery rehabilitation or following a muscle strain.

Isometric Exercises for the Knee:

Isometric Strengthening

What is Isometric Contraction?

• Isometric exercises involve muscle contraction without joint movement.

• The muscle generates force, but the joint does not change position.

• Quad Sets (quadriceps contraction without knee movement):

  • How to do it: Sit with your leg extended, tighten your quadriceps (front thigh muscle) by pushing the knee down into the floor, and hold for 5-10 seconds.

• Hamstring Sets (hamstring contraction without knee movement):

  • How to do it: Sit or lie with your knee extended and contract the hamstrings by pushing the heel into the floor or against a surface for 5-10 seconds.

Benefits for the Knee:

• Improves muscle strength around the knee joint without stressing the joint itself.

• Useful for post-surgery rehabilitation (e.g., after ACL or meniscus surgery) where movement may initially be limited.

• Reduces atrophy (muscle wasting) and helps maintain muscle tone.

• Reduces pain by improving neuromuscular activation.

Concentric Strengthening

What is Concentric Contraction?

• Concentric exercises involve the muscle shortening while generating force to move a joint.

• This is the type of contraction used when muscles work to accelerate movement.

Concentric Exercises for the Knee:

• Leg Extensions:

  • How to do it: Sit on a leg extension machine, straighten the knee to extend the leg, then slowly return to the starting position.

• Squats (with controlled knee flexion):

  • How to do it: With feet shoulder-width apart, squat down and push back up to standing position. Ensure the knee does not pass over the toes to avoid strain.

• Step-Ups:

  • How to do it: Step up onto a box or bench and then step down.

Benefits for the Knee:

• Strengthens quadriceps and hamstrings, key muscles that stabilize and control the knee joint.

• Improves muscular endurance and power for daily activities and sports.

• Enhances functional mobility and balance.

• Good for rehabilitating knee injuries where muscle strengthening is needed for joint stability.

Open-Chain Exercises

What is Open-Chain Exercise?

• Open-chain exercises occur when the distal part of the limb (foot or hand) is free to move while the proximal part (thigh or torso) is fixed or stationary.

• Typically, the knee joint is the primary focus of these exercises.

Open-Chain Knee Exercises:

• Leg Extensions (as mentioned above): The knee is the moving joint, and the foot/ankle is fixed.

• Straight Leg Raises (SLR):

  • How to do it: Lie flat, keeping the opposite leg bent, and raise one leg straight up while keeping the knee locked.

• Hip Flexor Stretch:

  • How to do it: This helps reduce tightness that may affect knee motion, which can be helpful for open-chain knee exercises.

Benefits for the Knee:

• Targets quadriceps and hamstring muscles individually.

• Focuses on isolated joint movement (specific range of motion).

• Good for strengthening the knee extensors (quads) after surgery or injury.

• Allows for precise and controlled strengthening of the knee joint muscles.

Concerns in Open-Chain for Knee Rehab:

• Increased shear forces on the knee joint (e.g., during leg extensions) can be risky in early rehab stages, especially post-ACL reconstruction.

• Should be carefully monitored to avoid overloading the joint or risking injury.

Closed-Chain Exercises

What is Closed-Chain Exercise?

• Closed-chain exercises involve movements where the distal part of the limb (foot) is fixed against a surface (such as the floor or a piece of equipment), and the proximal part (thigh or pelvis) moves.

• These exercises generally involve multi-joint movements and are more functional because they mimic real-world activities.

Closed-Chain Knee Exercises:

• Squats (Bodyweight or Weighted):

  • How to do it: Lower the body as if sitting in a chair, making sure the knees don’t go beyond the toes, and then stand back up.

• Lunges:

  • How to do it: Step forward and bend both knees to 90 degrees, then return to standing.

• Wall Sits:

  • How to do it: Lean against a wall, bend the knees to 90 degrees, and hold the position to engage the quadriceps.

• Leg Press Machine:

  • How to do it: In a controlled manner, push the weight up with your feet, extending the knees without locking them.

Benefits for the Knee:

• More functional for real-life activities (e.g., walking, climbing stairs).

• Less stress on the knee joint due to joint stability from the foot being fixed.

• Improves coordination of multiple muscles, making these exercises more functional.

• Engages stabilizing muscles (e.g., glutes, core), which are essential for knee function.

Benefits for Knee Rehabilitation:

• Rehabilitates the knee joint in a weight-bearing position, which is more beneficial for the functional use of the knee.

• Less risk of shear forces, making it safer post-surgery, especially after ACL or meniscus repair.

Key Differences:

Which Exercise is Best for the Knee?

• Early Stage Rehab: Start with isometric exercises to maintain strength and control pain.

• Mid to Late Stage Rehab: Include concentric and closed-chain exercises for joint stability and muscle strength.

• Open-Chain exercises can be added as the knee regains mobility and stability (particularly for ACL rehab once cleared by a therapist).