8. Knee Ligaments, Joints, Meniscus, Bursae, and Injuries
Ligaments of the Knee
Collateral Ligaments (MCL & LCL):
Medial Collateral Ligament (MCL) and Lateral Collateral Ligament (LCL) are located more on the outside, within the joint space.
They are palpable with fingers to check for pain.
Cruciate Ligaments (ACL & PCL):
Anterior Cruciate Ligament (ACL) and Posterior Cruciate Ligament (PCL) are not palpable.
Their integrity is assessed using special tests; a positive test suggests a tear.
Anterior Cruciate Ligament (ACL)
Function: Prevents anterior translation of the tibia on the femur.
Example: Stops the lower part of the leg from sliding forward in the knee joint when the knee is bent.
Special Test: Anterior drawer test, which mimics the movement the ACL prevents.
Mechanism of Injury (MOI): Commonly seen with pivoting and cutting movements (planting and twisting) leading to an abrupt change of direction and speed. A direct blow can also cause damage.
Signs & Symptoms:
Often described as a "big pop" sound, similar to an Achilles tendon rupture.
Immediate and significant swelling occurs within hours. Note: If an athlete claims no swelling, an ACL tear is highly unlikely.
Posterior Cruciate Ligament (PCL)
Function: Inhibits posterior translation of the tibia on the femur.
Example: Stops the tibia from sagging backward on the femur when the knee is bent.
Special Test: Sag sign. When the knee is bent, and the quad is relaxed, the tibia will sag backward. Contracting the quad will pull the tibia forward.
Mechanism of Injury (MOI): Commonly injured during hyperextension (leg fully extended and then forced beyond normal range) or a direct blow to the anterior tibia (e.g., "dashboard injury" where the knee strikes the dashboard).
Signs & Symptoms: Swelling may or may not be present, or it can be mild compared to an ACL tear.
Medial Collateral Ligament (MCL)
Function: Provides support against valgus stress (where the knees come together).
Mnemonic: "Genuvalgum" (knock-knees) – knees stuck together like "gum."
Mechanism of Injury (MOI): Typically results from a blow to the outside of the knee, causing a valgus stress. Can also be damaged by twisting with a planted foot. Common in contact sports (football, hockey, rugby).
Signs & Symptoms:
Probable swelling, though it can be localized.
Medial knee pain and tenderness on palpation along the MCL.
Discomfort with valgus stress during examination (patient may tense up to protect).
Unhappy Triad: A common simultaneous injury involving the ACL, MCL, and the medial meniscus from a single traumatic event (often planting, cutting, and twisting).
Surgical Considerations: Often managed conservatively if isolated and the ACL is intact. Surgery may be considered if there is an associated ACL tear.
Lateral Collateral Ligament (LCL)
Function: Provides support against varus stress (where the knees bow outwards).
Mechanism of Injury (MOI): Typically results from a blow to the inside of the knee, causing a varus stress. Can also occur with sudden twisting or hyperextension with a planted foot.
Prevalence: Least common knee ligament injury due to the protection offered by the other limb during contact.
Signs & Symptoms:
Lateralized knee pain (localized to the outside).
Localized swelling.
Tenderness on palpation along the LCL (from its attachment down to the fibular head).
Discomfort with varus stress (even in the absence of laxity for partial tears).
Unique Attachment: The LCL is the only knee ligament that attaches to the fibular head.
Articulations of the Knee
The knee joint is composed of three distinct articulations:
Tibiofemoral Joint: The true knee joint, formed between the femur and the tibia.
Patellofemoral Joint: Formed by the patella (kneecap) articulating with the femur. The patella "sits on top and floats" on the femur; there is no articulation between the patella and the tibia.
Proximal Tibiofibular Joint: Articulation between the tibia and the fibula.
Meniscus
Function: Act as shock absorbers, providing protection and cushioning for the knee joint. Crucial for sports involving jumping, planting, or twisting.
Shape:
Medial Meniscus: C-shaped.
Lateral Meniscus: O-shaped.
Common Injury: The medial meniscus is more commonly injured due to its C-shape, which covers less surface area and provides less protection than the lateral meniscus (which is partly protected by the fibula).
Association: The medial meniscus is a component of the Unhappy Triad (along with ACL and MCL).
Bursae of the Knee
Function: Small, fluid-filled sacs that assist the synovial membrane with lubrication and reduce friction in areas of high stress.
Clinical Significance: Important to differentiate swelling within the joint (intra-articular, e.g., ACL tear) from swelling in a bursa (due to biomechanical issues or direct trauma).
Key Bursae:
Prepatellar Bursa: Located in front of the patella, between the kneecap and the skin. Swelling presents as a distinct "golf ball" lump directly on top of the kneecap.
Infrapatellar Bursas (Superficial & Deep): Located below the kneecap, around the patellar tendon. Swelling is generally less distinct than the prepatellar bursa.
Suprapatellar Bursa: Located between the quadriceps muscles and the femur, above the knee joint. Swelling appears above the kneecap, almost under the quad.
Pes Anserine Bursa: Located medial and inferior to the tibial tuberosity. It lies beneath the tendons of the sartorius, gracilis, and semitendinosus muscles (the "pes anserinus" or "goose's foot" insertion). Inflammation here is called pes anserine bursitis, often presenting with redness and heat, and is the most common cause of medial knee pain in runners.
Knee Abnormalities (Genu Deformities)
Observation: Assessed during observation of the lower limbs, progressing from feet (e.g., pes planus/cavus) upwards.
Genu Varum (Bowleg): Knees bow outwards. Anatomical presentation.
Genu Valgum (Knock-knees): Knees bow inwards (like "gum" sticking them together). Anatomical presentation.
Clinical Note: These deformities are anatomical findings. If asymptomatic, they are not treated as pathologies but are important to note.
Clinical Implications:
Genu Varum: Increased stress on the lateral compartment of the knee.
Both Genu Varum and Genu Valgum: Increase the risk of patellofemoral pain syndrome (PFPS) due to an altered Q-angle, which affects patella tracking.
Patellar Position Abnormalities
Assessment: Observed standing and supine.
Patella Baja: A low-riding patella that sits more over the actual joint line when the leg is extended.
Patella Alta: A high-riding patella, appearing almost dislocated or subluxated, not sitting deeply in the patellofemoral groove.
Squinting Patella: Patellas that are more medially placed.
Frog Eye Patella: Patellas that are more laterally placed.
Asymmetry: Unilateral abnormalities may indicate previous surgical interventions, especially those for patellar dislocation (e.g., lateral retinaculum tightening).
Specific Knee Injuries: PCL Sprains
Mechanism of Injury (MOI):
"Dashboard injury": A direct blow to the anterior aspect of a flexed knee.
Hyperextension of the knee.
Signs & Symptoms:
Posterior knee pain (front of the knee often not sore acutely).
Mild swelling compared to an ACL tear.
Feelings of instability, especially when going downstairs or downhill.
Pain with squatting and kneeling.
Chronic PCL Injury: Can lead to anterior knee pain and quadriceps tendinitis or patellofemoral joint pain due to the quadriceps compensating for the PCL's function.
Management (Grade I-II / Partial Tear):
RICE: Rest, Ice, Compression, Elevation.
Immobilization: Use of a brace that prevents posterior translation, often a hinged brace that keeps the tibia in an anterior position.
Strengthening: Focus on quadriceps strengthening to pull the tibia forward.
Avoid: Isolated hamstring movements, as they can pull the tibia further posteriorly.
Management (Grade III / Complete Tear): Most likely involves surgical intervention.
Specific Knee Injuries: ACL Sprains
Mechanism of Injury (MOI):
Non-contact (Most Common): Cutting or pivoting movements, involving abrupt changes in direction and speed.
Contact: A direct blow to the knee, usually from lateral to medial.
Signs & Symptoms:
Often a distinct "pop" sound (similar to an Achilles rupture).
Immediate, significant swelling (hemosarthrosis) within hours.
Feelings of instability, the leg "giving out," or not being trusted during walking or pivoting movements.
Management:
RICE: Rest, Ice, Compression, Elevation.
Immobilization/Bracing: Functional bracing to provide support.
Control swelling and pain.
Strengthening: Focus on both quadriceps and hamstrings.
Surgical Intervention: Considered for Grade 3+ tears or if conservative management fails to allow satisfactory return to function. Often involves grafting.
Specific Knee Injuries: LCL Sprains
Mechanism of Injury (MOI):
A varus force applied to the knee (a blow to the inside of the knee forcing the knee outwards).
Sudden twisting or hyperextension with the foot planted.
Prevalence: It is the least common of the major knee ligament injuries, often protected by the other limb during contact.
Signs & Symptoms:
Lateral knee pain.
Localized swelling on the outside of the knee.
Tenderness on palpation along the LCL.
Discomfort with varus stress during examination.
Management:
RICE: Rest, Ice, Compression, Elevation.
Immobilization: A hinge brace for stability.
Strengthening: Hamstrings, quadriceps, and gluteal muscles (strengthening the entire complex).
Prognosis: Often Grade I or II; typically responds well to conservative treatment without surgery.
Specific Knee Injuries: MCL Sprains
Prevalence: One of the most common knee ligament injuries, comparable to ACL tears in frequency.
Mechanism of Injury (MOI):
A blow to the outside of the knee (imparting valgus stress).
Twisting motion with the foot planted.
Common in contact sports (e.g., football, hockey, rugby).
Signs & Symptoms:
Medial knee pain.
Localized swelling on the inside of the knee.
Tenderness on palpation along the MCL.
Pain and discomfort with a valgus stress during examination (due to stretching of torn fibers).
Management:
RICE: Rest, Ice, Compression, Elevation.
Early mobilization with a hinge brace for stability.
Early range of motion exercises.
Strength training.
Gradual return to play.
Surgical Considerations: Surgical intervention for isolated MCL tears (especially Grade 3) is rare, particularly if the ACL is intact. However, if both MCL and ACL are torn (e.g., in an unhappy triad), surgery is more likely.
Specific Knee Injuries: IT Band Syndrome (ITBS) / ITB Friction Syndrome
Type: Overuse injury.
Common in: Runners and cyclists.
Mechanism: Repetitive knee flexion and extension (e.g., running, cycling) causes friction of the iliotibial band (ITB) over the lateral femoral condyle, leading to irritation and inflammation.
Contributing Factors:
Tightness in the IT band or gluteal muscles.
Weak gluteus medius (a hip stabilizer).
Overpronation of the foot (in runners).
Genu varum (bowlegs), which can increase the distance the ITB must travel over the condyle.
Signs & Symptoms:
Lateral knee pain.
Pain is worse with activity (running, cycling) and often subsides at rest.
May report a "snapping" sensation or sound during activity as the ITB passes over the condyle.
Management:
Acute Phase: Decrease inflammation (RICE).
Activity Modification: Reduce mileage, change terrain, consider insoles/inserts for overpronation, or strengthen feet.
Strength Training: Essential to strengthen gluteal and hip muscles to reduce stress on the ITB.
Specific Knee Injuries: Patellar Dislocation / Subluxation
Direction: Approximately 9 out of 10 patellar dislocations occur laterally.
Mechanism:
A valgus stress combined with external rotation of the tibia (e.g., cutting or pivoting movements).
A direct blow to the inside of the knee.
Predisposing Factors (often anatomical/genetic):
Patella Alta (high-riding patella).
A shallow trochlear groove (the groove in the femur where the patella sits).
Generalized ligamentous laxity.
Genu Valgum (knock-knees), which can cause the patella to be predisposed to a lateral position.
Signs & Symptoms (Acute):
Visible deformity, with the patella often clearly displaced laterally.
Severe anterior knee pain.
Inability to move the knee.
Huge, immediate swelling (similar to an ACL tear).
Pain on the medial side of the knee due to tearing of the medial retinaculum.
Spontaneous Reduction: Athletes may report the patella "popped back in" due to muscle activation or wiggling the leg.
Management (Post-Reduction):
Immobilization: A large leg cast for approximately 2 to 4 weeks.
Manage swelling and pain.
Gradual return to gentle range of motion, followed by strengthening, and then return to play.
Specific Knee Injuries: Jumper's Knee (Patellar Tendinopathy)
Type: Overuse injury.
Common in: Athletes involved in jumping and sprinting sports (e.g., basketball, volleyball, track and field), often seen in females.
Location: Inflammation or degeneration at the inferior pole of the patella where the patellar tendon attaches.
Short-term: Tendinitis (inflammation).
Long-term: Tendinopathy (structural tendon changes).
Causes: Often due to muscular imbalance, high training volume, load, or intensity. Typically involves very tight quadriceps muscles coupled with weak hamstrings and hip stabilizers, leading to excessive quad dominance in jumping activities.
Signs & Symptoms:
Pain located underneath the patella (the patella itself is usually not painful).
Pain is worse with jumping, running, squatting, and going down stairs.
Tenderness on palpation at the inferior pole of the patella.
Initially, pain occurs only with activity; if chronic, anterior knee pain can become constant.
Management:
No Immobilization: Movement is encouraged, not restricted.
Eccentric Loading: Focus on eccentric quadriceps exercises for proper patellar tendon healing and remodeling.
Activity modification.
Address muscular imbalances.
Specific Knee Injuries: Meniscus Tear
Types:
Acute Traumatic Injury: Occurs with twisting or pivoting movements when the knee is flexed. Common in sports (soccer, football, basketball). The most significant pressure on the meniscus occurs at 90^\circ of knee flexion.
Degenerative Chronic Injury: Age-related wear and tear from repetitive stress over time (e.g., construction workers with frequent squatting/kneeling).
Signs & Symptoms:
Medial or lateral knee pain, depending on the location of the tear.
Delayed Swelling: Swelling typically appears 2-3 days after the injury, unlike the immediate swelling seen with ACL tears or patellar dislocations. This is important to note and communicate to the patient.
"Locking or catching" sensation: The leg may feel stuck, requiring wiggling to regain range of motion.
Limited full range of motion (full flexion or extension may be incomplete).
Tenderness on palpation along the joint line (distinct from MCL palpation along the ligament itself).
Management:
RICE: Rest, Ice, Compression, Elevation.
Avoid twisting and deep bending (to reduce pressure on the meniscus).
Range of Motion (ROM) Exercises: Encouraged to maintain joint mobility and prevent seizing up; splinting is generally avoided.
Surgical Intervention: Considered for persistent knee locking or catching.
Assessment Overview
History
Key Questions: Who, what, how, when, where is the pain? Did they hear/feel anything (e.g., pop for ACL, snap for ITB)?
Information Gathering: Previous health history, current medications.
Observation
Bilateral Comparison: Always compare the injured knee to the uninjured side.
Visual Assessment: Look for swelling, discoloration, and deformities around the knee, as well as structures above and below.
Knee Position: Note genu varum (bowleg) or genu valgum (knock-knees).
Patellar Position: Observe patella baja (low-riding), patella alta (high-riding), squinting (medially placed), or frog eye (laterally placed) patellas.
Foot Position: Assess for pes planus (flat feet) or pes cavus (high arches), as these can impact knee biomechanics.
Comprehensive View: Examine the front, back, and sides of the knee for any abnormalities.
Palpation
Ligaments:
MCL & LCL: Palpable to identify localized pain.
ACL & PCL: Not palpable directly.
Muscles to Palpate:
Quadriceps.
Hamstrings.
Adductors.
Pes Anserine Complex: Medial and inferior to the tibial tuberosity, where the sartorius, gracilis, and semitendinosus muscles converge.
Bones to Palpate:
Patella.
Medial femoral condyle.
Lateral femoral condyle.
Fibular Head: Located laterally; confirm palpation by flexing and extending the knee without your hand moving.
Tibial condyles, tibial tuberosity, Gerdy's tubercle.
Other: Assess skin temperature and swelling using the back of the hands.
Pulses: Check the popliteal pulse, located behind the knee in the popliteal fossa.
Range of Motion (ROM) Assessment
Types: Active, passive, and resisted movements.
Knee: Primary movements are flexion and extension (a hinge joint).
Hip: Due to the kinetic chain, hip ROM (internal/external rotation, abduction/adduction, flexion) should also be assessed.
Goniometry (Q-Angle): The Q-angle represents the angle from the femur into the knee. Women typically have a larger Q-angle due to a wider pelvis, which is associated with a higher incidence of knee injuries.
Special Tests for the Knee
Special tests are performed to assess specific ligamentous or meniscal integrity, or patellar stability.
Valgus & Varus Stress Tests
Purpose: To assess the integrity of the collateral ligaments (MCL for valgus, LCL for varus) for pain and laxity.
Procedure:
Valgus Stress: The distal part of the lower leg moves away from the midline (testing MCL).
Varus Stress: The distal part of the lower leg moves towards the midline (testing LCL).
Execution: Tests are performed with the knee fully extended and also slightly flexed.
Anterior & Posterior Drawer Tests
Purpose: To assess the integrity of the cruciate ligaments (ACL for anterior, PCL for posterior) for pain and laxity.
Procedure: Patient lies supine with the knee flexed at 90^\circ. The examiner's hands are used to:
Anterior Drawer: Pull the tibia forward (testing ACL – like opening a drawer).
Posterior Drawer: Push the tibia backward (testing PCL).
Clinical Note: Female athletes may exhibit false positive laxity in ACL/PCL during certain phases of their menstrual cycle.
Posterior Sag Test
Purpose: To assess the integrity of the PCL.
Procedure: Patient lies supine with the knee flexed at 90^\circ. Observe if the tibia sags posteriorly. Asking the patient to contract their quadriceps should pull the tibia anteriorly, reducing the sag.
Ober's Test
Purpose: To assess for tightness of the iliotibial band (ITB).
Procedure: Patient lies on their non-affected side. The affected leg is extended and abducted by the examiner, then gently lowered.
Positive Result: Pain, a palpable "pop" as the ITB moves over the lateral femoral condyle, or the leg remaining elevated due to tightness or pain.
McMurray's Test
Purpose: To assess for a meniscal injury.
Procedure: Patient lies supine. One hand is placed on the knee, and the other on the foot. The examiner applies axial compression to the knee joint while simultaneously rotating the tibia medially and laterally.
Positive Result: Pain, popping, clicking, or a locking sensation (inability for further rotation).
Thessaly's Test
Purpose: To assess for a meniscal injury (often performed as a weight-bearing alternative to McMurray's).
Procedure: Patient stands on one leg with the knee slightly flexed (around 20^\circ). The patient then rotates their body from side to side.
Positive Result: Pain, popping, clicking, or a locking sensation. Often considered highly sensitive due to weight-bearing.
Apprehension Test (for Patellar Subluxation)
Purpose: To assess for patellar instability and risk of subluxation or dislocation.
Procedure: Patient lies supine with legs relaxed. The examiner gently attempts to move the patella laterally.
Positive Result: The patient contracts their quadriceps muscles or displays apprehension/fear, attempting to prevent the patella from further lateral displacement, indicating potential instability.
Injury Mechanisms (Video Examples)
Lateral Blow to the Knee with Foot Planted: High risk of ACL rupture and the "Unhappy Triad" (ACL, MCL, medial meniscus).
Hyperextension: Primarily associated with PCL injury, but can involve other structures in severe cases.
Severe Knee Trauma/Dislocation (e.g., "Tank Dell" injury): Can involve multiple ligamentous and bony structures due to extreme forces.
Notes Rewrite:
ACL function:
Prevents anterior translation of the tibia; sliding forward on femur when the knee is bent.
Ligaments of the Knee
Collateral Ligaments (MCL & LCL): Located centrally within the joint space and palpable; MCL on the medial side, LCL on the lateral side.
Cruciate Ligaments (ACL & PCL): Not palpable; assessed via special tests. ACL prevents anterior tibial translation, PCL prevents posterior tibial translation.
Anterior Cruciate Ligament (ACL)
Function: Prevents anterior translation of the tibia on the femur.
MOI: Pivoting, cutting, direct blow.
Signs & Symptoms: "Big pop," immediate significant swelling (hemosarthrosis), instability.
Posterior Cruciate Ligament (PCL)
Function: Inhibits posterior translation of the tibia on the femur.
MOI: Hyperextension, direct blow to anterior tibia ("dashboard injury").
Signs & Symptoms: Sag sign, mild or absent swelling.
Medial Collateral Ligament (MCL)
Function: Supports against valgus stress (knees come together, like "gum").
MOI: Blow to the outside of the knee.
Signs & Symptoms: Medial knee pain, localized swelling, tenderness on palpation, discomfort with valgus stress.
Unhappy Triad: Concomitant ACL, MCL, and medial meniscus injury.
Lateral Collateral Ligament (LCL)
Function: Supports against varus stress (knees bow outwards).
MOI: Blow to the inside of the knee.
Prevalence: Least common knee ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness on palpation along LCL to fibular head.
Unique Attachment: Only knee ligament attaching to the fibular head.
Articulations of the Knee
Tibiofemoral Joint: Femur and tibia.
Patellofemoral Joint: Patella and femur (no patella-tibia articulation).
Proximal Tibiofibular Joint: Tibia and fibula.
Meniscus
Function: Shock absorbers and cushioning. Medial is C-shaped, Lateral is O-shaped.
Common Injury: Medial meniscus (less surface area, part of Unhappy Triad).
Bursae of the Knee
Function: Fluid-filled sacs reducing friction and lubricating. Differentiate from intra-articular swelling.
Key Bursae:
Prepatellar: On kneecap ("golf ball" lump).
Infrapatellar: Below kneecap.
Suprapatellar: Above kneecap.
Pes Anserine: Medial and inferior to tibial tuberosity; prone to bursitis in runners; most common cause of medial knee pain in runners.
Knee Abnormalities (Genu Deformities)
Genu Varum (Bowleg): Knees bow outwards; increases lateral compartment stress.
Genu Valgum (Knock-knees): Knees bow inwards; increases risk of patellofemoral pain syndrome (PFPS) due to altered Q-angle.
Patellar Position Abnormalities
Patella Baja: Low-riding patella.
Patella Alta: High-riding patella.
Squinting Patella: Medially placed.
Frog Eye Patella: Laterally placed.
Specific Knee Injuries: PCL Sprains
MOI: "Dashboard injury," hyperextension.
Signs & Symptoms: Posterior knee pain, mild swelling, instability (especially downhill/stairs), chronic can lead to anterior knee pain.
Management: RICE, immobilization, quadriceps strengthening (avoid isolated hamstrings).
Specific Knee Injuries: ACL Sprains
MOI: Non-contact (cutting/pivoting) or direct blow.
Signs & Symptoms: "Pop," immediate significant swelling, instability.
Management: RICE, bracing, quad/hamstring strengthening. Surgery for Grade 3+ tears.
Specific Knee Injuries: LCL Sprains
MOI: Varus force (blow to inside of knee).
Prevalence: Least common ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness.
Management: RICE, hinge brace, full complex strengthening. Responds well to conservative treatment.
Specific Knee Injuries: MCL Sprains
Prevalence: Common (comparable to ACL).
MOI: Valgus force (blow to outside of knee).
Signs & Symptoms: Medial knee pain, localized swelling, tenderness, pain with valgus stress.
Management: RICE, early mobilization/ROM/strengthening. Surgery rare for isolated tears; more likely if ACL co-injured.
Specific Knee Injuries: IT Band Syndrome (ITBS) / ITB Friction Syndrome
Type: Overuse injury; common in runners/cyclists.
Mechanism: Friction of ITB over lateral femoral condyle from repetitive flexion/extension.
Signs & Symptoms: Lateral knee pain, worse with activity, may have "snapping."
Management: RICE, activity modification, gluteal/hip strengthening.
Specific Knee Injuries: Patellar Dislocation / Subluxation
Direction: ~9 in 10 are lateral.
MOI: Valgus stress + external tibial rotation, or direct blow.
Predisposing Factors: Patella alta, shallow trochlear groove, ligamentous laxity, genu valgum.
Signs & Symptoms: Visible deformity, severe anterior knee pain, immediate swelling, pain medial side (medial retinaculum tear).
Management: Post-reduction immobilization (2-4 weeks cast), rehab.
Specific Knee Injuries: Jumper's Knee (Patellar Tendinopathy)
Type: Overuse injury; common in jumping/sprinting athletes.
Location: Inferior pole of patella.
Causes: Muscular imbalance (quad dominance), high training volume.
Signs & Symptoms: Pain underneath patella, worse with jumping/squatting, tenderness at inferior pole. No immobilization; eccentric quad exercises.
Specific Knee Injuries: Meniscus Tear
Types: Acute (twisting, pivoting with flexed knee) or Degenerative (age-related wear).
Signs & Symptoms: Medial/lateral knee pain, delayed swelling (2-3 days), "locking/catching," limited ROM, joint line tenderness.
Management: RICE, avoid twisting/deep bending, ROM exercises. Surgery for persistent locking/catching.
Assessment Overview
History: Who, what, how, when, where pain; previous health.
Observation: Bilateral comparison for swelling, discoloration, deformities (genu varum/valgum, patellar position, foot position).
Palpation: MCL/LCL palpable; specific muscles/bones, skin temperature, popliteal pulse.
Range of Motion (ROM): Active, passive, resisted knee flexion/extension; hip ROM; Q-angle assessment.
Special Tests for the Knee
Valgus/Varus Stress: Collateral ligament integrity.
Anterior/Posterior Drawer: Cruciate ligament integrity.
Posterior Sag: PCL integrity.
Ober's Test: ITB tightness.
McMurray's Test: Meniscal injury (axial compression + tibial rotation).
Thessaly's Test: Meniscal injury (weight-bearing rotation).
Apprehension Test: Patellar instability (lateral patellar movement).
Injury Mechanisms (Video Examples)
Lateral Blow with Foot Planted: High risk ACL rupture, Unhappy Triad.
Hyperextension: Primarily PCL injury.
Severe Trauma: Multiple ligamentous/bony structures.
Ligaments of the Knee
Collateral Ligaments (MCL & LCL): Located centrally within the joint space and palpable; MCL on the medial side, LCL on the lateral side.
Cruciate Ligaments (ACL & PCL): Not palpable; assessed via special tests. ACL prevents anterior tibial translation, PCL prevents posterior tibial translation.
Anterior Cruciate Ligament (ACL)
Function: Prevents anterior translation of the tibia on the femur.
MOI: Pivoting, cutting, direct blow.
Signs & Symptoms: "Big pop," immediate significant swelling (hemosarthrosis), instability.
Posterior Cruciate Ligament (PCL)
Function: Inhibits posterior translation of the tibia on the femur.
MOI: Hyperextension, direct blow to anterior tibia ("dashboard injury").
Signs & Symptoms: Sag sign, mild or absent swelling.
Medial Collateral Ligament (MCL)
Function: Supports against valgus stress (knees come together, like "gum").
MOI: Blow to the outside of the knee.
Signs & Symptoms: Medial knee pain, localized swelling, tenderness on palpation, discomfort with valgus stress.
Unhappy Triad: Concomitant ACL, MCL, and medial meniscus injury.
Lateral Collateral Ligament (LCL)
Function: Supports against varus stress (knees bow outwards).
MOI: Blow to the inside of the knee.
Prevalence: Least common knee ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness on palpation along LCL to fibular head.
Unique Attachment: Only knee ligament attaching to the fibular head.
Articulations of the Knee
Tibiofemoral Joint: Femur and tibia.
Patellofemoral Joint: Patella and femur (no patella-tibia articulation).
Proximal Tibiofibular Joint: Tibia and fibula.
Meniscus
Function: Shock absorbers and cushioning. Medial is C-shaped, Lateral is O-shaped.
Common Injury: Medial meniscus (less surface area, part of Unhappy Triad).
Bursae of the Knee
Function: Fluid-filled sacs reducing friction and lubricating. Differentiate from intra-articular swelling.
Key Bursae:
Prepatellar: On kneecap ("golf ball" lump).
Infrapatellar: Below kneecap.
Suprapatellar: Above kneecap.
Pes Anserine: Medial and inferior to tibial tuberosity; prone to bursitis in runners; most common cause of medial knee pain in runners.
Knee Abnormalities (Genu Deformities)
Genu Varum (Bowleg): Knees bow outwards; increases lateral compartment stress.
Genu Valgum (Knock-knees): Knees bow inwards; increases risk of patellofemoral pain syndrome (PFPS) due to altered Q-angle.
Patellar Position Abnormalities
Patella Baja: Low-riding patella.
Patella Alta: High-riding patella.
Squinting Patella: Medially placed.
Frog Eye Patella: Laterally placed.
Specific Knee Injuries: PCL Sprains
MOI: "Dashboard injury," hyperextension.
Signs & Symptoms: Posterior knee pain, mild swelling, instability (especially downhill/stairs), chronic can lead to anterior knee pain.
Management: RICE, immobilization, quadriceps strengthening (avoid isolated hamstrings).
Specific Knee Injuries: ACL Sprains
MOI: Non-contact (cutting/pivoting) or direct blow.
Signs & Symptoms: "Pop," immediate significant swelling, instability.
Management: RICE, bracing, quad/hamstring strengthening. Surgery for Grade 3+ tears.
Specific Knee Injuries: LCL Sprains
MOI: Varus force (blow to inside of knee).
Prevalence: Least common ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness.
Management: RICE, hinge brace, full complex strengthening. Responds well to conservative treatment.
Specific Knee Injuries: MCL Sprains
Prevalence: Common (comparable to ACL).
MOI: Valgus force (blow to outside of knee).
Signs & Symptoms: Medial knee pain, localized swelling, tenderness, pain with valgus stress.
Management: RICE, early mobilization/ROM/strengthening. Surgery rare for isolated tears; more likely if ACL co-injured.
Specific Knee Injuries: IT Band Syndrome (ITBS) / ITB Friction Syndrome
Type: Overuse injury; common in runners/cyclists.
Mechanism: Friction of ITB over lateral femoral condyle from repetitive flexion/extension.
Signs & Symptoms: Lateral knee pain, worse with activity, may have "snapping."
Management: RICE, activity modification, gluteal/hip strengthening.
Specific Knee Injuries: Patellar Dislocation / Subluxation
Direction: ~9 in 10 are lateral.
MOI: Valgus stress + external tibial rotation, or direct blow.
Predisposing Factors: Patella alta, shallow trochlear groove, ligamentous laxity, genu valgum.
Signs & Symptoms: Visible deformity, severe anterior knee pain, immediate swelling, pain medial side (medial retinaculum tear).
Management: Post-reduction immobilization (2-4 weeks cast), rehab.
Specific Knee Injuries: Jumper's Knee (Patellar Tendinopathy)
Type: Overuse injury; common in jumping/sprinting athletes.
Location: Inferior pole of patella.
Causes: Muscular imbalance (quad dominance), high training volume.
Signs & Symptoms: Pain underneath patella, worse with jumping/squatting, tenderness at inferior pole. No immobilization; eccentric quad exercises.
Specific Knee Injuries: Meniscus Tear
Types: Acute (twisting, pivoting with flexed knee) or Degenerative (age-related wear).
Signs & Symptoms: Medial/lateral knee pain, delayed swelling (2-3 days), "locking/catching," limited ROM, joint line tenderness.
Management: RICE, avoid twisting/deep bending, ROM exercises. Surgery for persistent locking/catching.
Assessment Overview
History: Who, what, how, when, where pain; previous health.
Observation: Bilateral comparison for swelling, discoloration, deformities (genu varum/valgum, patellar position, foot position).
Palpation: MCL/LCL palpable; specific muscles/bones, skin temperature, popliteal pulse.
Range of Motion (ROM): Active, passive, resisted knee flexion/extension; hip ROM; Q-angle assessment.
Special Tests for the Knee
Valgus/Varus Stress: Collateral ligament integrity.
Anterior/Posterior Drawer: Cruciate ligament integrity.
Posterior Sag: PCL integrity.
Ober's Test: ITB tightness.
McMurray's Test: Meniscal injury (axial compression + tibial rotation).
Thessaly's Test: Meniscal injury (weight-bearing rotation).
Apprehension Test: Patellar instability (lateral patellar movement).
Injury Mechanisms (Video Examples)
Lateral Blow with Foot Planted: High risk ACL rupture, Unhappy Triad.
Hyperextension: Primarily PCL injury.
Severe Trauma: Multiple ligamentous/bony structures.
Ligaments of the Knee
Collateral Ligaments (MCL & LCL): Located centrally within the joint space and palpable; MCL on the medial side, LCL on the lateral side.
Cruciate Ligaments (ACL & PCL): Not palpable; assessed via special tests. ACL prevents anterior tibial translation, PCL prevents posterior tibial translation.
Anterior Cruciate Ligament (ACL)
Function: Prevents anterior translation of the tibia on the femur.
MOI: Pivoting, cutting, direct blow.
Signs & Symptoms: "Big pop," immediate significant swelling (hemosarthrosis), instability.
Posterior Cruciate Ligament (PCL)
Function: Inhibits posterior translation of the tibia on the femur.
MOI: Hyperextension, direct blow to anterior tibia ("dashboard injury").
Signs & Symptoms: Sag sign, mild or absent swelling.
Medial Collateral Ligament (MCL)
Function: Supports against valgus stress (knees come together, like "gum").
MOI: Blow to the outside of the knee.
Signs & Symptoms: Medial knee pain, localized swelling, tenderness on palpation, discomfort with valgus stress.
Unhappy Triad: Concomitant ACL, MCL, and medial meniscus injury.
Lateral Collateral Ligament (LCL)
Function: Supports against varus stress (knees bow outwards).
MOI: Blow to the inside of the knee.
Prevalence: Least common knee ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness on palpation along LCL to fibular head.
Unique Attachment: Only knee ligament attaching to the fibular head.
Articulations of the Knee
Tibiofemoral Joint: Femur and tibia.
Patellofemoral Joint: Patella and femur (no patella-tibia articulation).
Proximal Tibiofibular Joint: Tibia and fibula.
Meniscus
Function: Shock absorbers and cushioning. Medial is C-shaped, Lateral is O-shaped.
Common Injury: Medial meniscus (less surface area, part of Unhappy Triad).
Bursae of the Knee
Function: Fluid-filled sacs reducing friction and lubricating. Differentiate from intra-articular swelling.
Key Bursae:
Prepatellar: On kneecap ("golf ball" lump).
Infrapatellar: Below kneecap.
Suprapatellar: Above kneecap.
Pes Anserine: Medial and inferior to tibial tuberosity; prone to bursitis in runners; most common cause of medial knee pain in runners.
Knee Abnormalities (Genu Deformities)
Genu Varum (Bowleg): Knees bow outwards; increases lateral compartment stress.
Genu Valgum (Knock-knees): Knees bow inwards; increases risk of patellofemoral pain syndrome (PFPS) due to altered Q-angle.
Patellar Position Abnormalities
Patella Baja: Low-riding patella.
Patella Alta: High-riding patella.
Squinting Patella: Medially placed.
Frog Eye Patella: Laterally placed.
Specific Knee Injuries: PCL Sprains
MOI: "Dashboard injury," hyperextension.
Signs & Symptoms: Posterior knee pain, mild swelling, instability (especially downhill/stairs), chronic can lead to anterior knee pain.
Management: RICE, immobilization, quadriceps strengthening (avoid isolated hamstrings).
Specific Knee Injuries: ACL Sprains
MOI: Non-contact (cutting/pivoting) or direct blow.
Signs & Symptoms: "Pop," immediate significant swelling, instability.
Management: RICE, bracing, quad/hamstring strengthening. Surgery for Grade 3+ tears.
Specific Knee Injuries: LCL Sprains
MOI: Varus force (blow to inside of knee).
Prevalence: Least common ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness.
Management: RICE, hinge brace, full complex strengthening. Responds well to conservative treatment.
Specific Knee Injuries: MCL Sprains
Prevalence: Common (comparable to ACL).
MOI: Valgus force (blow to outside of knee).
Signs & Symptoms: Medial knee pain, localized swelling, tenderness, pain with valgus stress.
Management: RICE, early mobilization/ROM/strengthening. Surgery rare for isolated tears; more likely if ACL co-injured.
Specific Knee Injuries: IT Band Syndrome (ITBS) / ITB Friction Syndrome
Type: Overuse injury; common in runners/cyclists.
Mechanism: Friction of ITB over lateral femoral condyle from repetitive flexion/extension.
Signs & Symptoms: Lateral knee pain, worse with activity, may have "snapping."
Management: RICE, activity modification, gluteal/hip strengthening.
Specific Knee Injuries: Patellar Dislocation / Subluxation
Direction: ~9 in 10 are lateral.
MOI: Valgus stress + external tibial rotation, or direct blow.
Predisposing Factors: Patella alta, shallow trochlear groove, ligamentous laxity, genu valgum.
Signs & Symptoms: Visible deformity, severe anterior knee pain, immediate swelling, pain medial side (medial retinaculum tear).
Management: Post-reduction immobilization (2-4 weeks cast), rehab.
Specific Knee Injuries: Jumper's Knee (Patellar Tendinopathy)
Type: Overuse injury; common in jumping/sprinting athletes.
Location: Inferior pole of patella.
Causes: Muscular imbalance (quad dominance), high training volume.
Signs & Symptoms: Pain underneath patella, worse with jumping/squatting, tenderness at inferior pole. No immobilization; eccentric quad exercises.
Specific Knee Injuries: Meniscus Tear
Types: Acute (twisting, pivoting with flexed knee) or Degenerative (age-related wear).
Signs & Symptoms: Medial/lateral knee pain, delayed swelling (2-3 days), "locking/catching," limited ROM, joint line tenderness.
Management: RICE, avoid twisting/deep bending, ROM exercises. Surgery for persistent locking/catching.
Assessment Overview
History: Who, what, how, when, where pain; previous health.
Observation: Bilateral comparison for swelling, discoloration, deformities (genu varum/valgum, patellar position, foot position).
Palpation: MCL/LCL palpable; specific muscles/bones, skin temperature, popliteal pulse.
Range of Motion (ROM): Active, passive, resisted knee flexion/extension; hip ROM; Q-angle assessment.
Special Tests for the Knee
Valgus/Varus Stress: Collateral ligament integrity.
Anterior/Posterior Drawer: Cruciate ligament integrity.
Posterior Sag: PCL integrity.
Ober's Test: ITB tightness.
McMurray's Test: Meniscal injury (axial compression + tibial rotation).
Thessaly's Test: Meniscal injury (weight-bearing rotation).
Apprehension Test: Patellar instability (lateral patellar movement).
Injury Mechanisms (Video Examples)
Lateral Blow with Foot Planted: High risk ACL rupture, Unhappy Triad.
Hyperextension: Primarily PCL injury.
Severe Trauma: Multiple ligamentous/bony structures.
Ligaments of the Knee
Collateral Ligaments (MCL & LCL): Located centrally within the joint space and palpable; MCL on the medial side, LCL on the lateral side.
Cruciate Ligaments (ACL & PCL): Not palpable; assessed via special tests. ACL prevents anterior tibial translation, PCL prevents posterior tibial translation.
Anterior Cruciate Ligament (ACL)
Function: Prevents anterior translation of the tibia on the femur.
MOI: Pivoting, cutting, direct blow.
Signs & Symptoms: "Big pop," immediate significant swelling (hemosarthrosis), instability.
Posterior Cruciate Ligament (PCL)
Function: Inhibits posterior translation of the tibia on the femur.
MOI: Hyperextension, direct blow to anterior tibia ("dashboard injury").
Signs & Symptoms: Sag sign, mild or absent swelling.
Medial Collateral Ligament (MCL)
Function: Supports against valgus stress (knees come together, like "gum").
MOI: Blow to the outside of the knee.
Signs & Symptoms: Medial knee pain, localized swelling, tenderness on palpation, discomfort with valgus stress.
Unhappy Triad: Concomitant ACL, MCL, and medial meniscus injury.
Lateral Collateral Ligament (LCL)
Function: Supports against varus stress (knees bow outwards).
MOI: Blow to the inside of the knee.
Prevalence: Least common knee ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness on palpation along LCL to fibular head.
Unique Attachment: Only knee ligament attaching to the fibular head.
Articulations of the Knee
Tibiofemoral Joint: Femur and tibia.
Patellofemoral Joint: Patella and femur (no patella-tibia articulation).
Proximal Tibiofibular Joint: Tibia and fibula.
Meniscus
Function: Shock absorbers and cushioning. Medial is C-shaped, Lateral is O-shaped.
Common Injury: Medial meniscus (less surface area, part of Unhappy Triad).
Bursae of the Knee
Function: Fluid-filled sacs reducing friction and lubricating. Differentiate from intra-articular swelling.
Key Bursae:
Prepatellar: On kneecap ("golf ball" lump).
Infrapatellar: Below kneecap.
Suprapatellar: Above kneecap.
Pes Anserine: Medial and inferior to tibial tuberosity; prone to bursitis in runners; most common cause of medial knee pain in runners.
Knee Abnormalities (Genu Deformities)
Genu Varum (Bowleg): Knees bow outwards; increases lateral compartment stress.
Genu Valgum (Knock-knees): Knees bow inwards; increases risk of patellofemoral pain syndrome (PFPS) due to altered Q-angle.
Patellar Position Abnormalities
Patella Baja: Low-riding patella.
Patella Alta: High-riding patella.
Squinting Patella: Medially placed.
Frog Eye Patella: Laterally placed.
Specific Knee Injuries: PCL Sprains
MOI: "Dashboard injury," hyperextension.
Signs & Symptoms: Posterior knee pain, mild swelling, instability (especially downhill/stairs), chronic can lead to anterior knee pain.
Management: RICE, immobilization, quadriceps strengthening (avoid isolated hamstrings).
Specific Knee Injuries: ACL Sprains
MOI: Non-contact (cutting/pivoting) or direct blow.
Signs & Symptoms: "Pop," immediate significant swelling, instability.
Management: RICE, bracing, quad/hamstring strengthening. Surgery for Grade 3+3+ tears.
Specific Knee Injuries: LCL Sprains
MOI: Varus force (blow to inside of knee).
Prevalence: Least common ligament injury.
Signs & Symptoms: Lateral knee pain, localized swelling, tenderness.
Management: RICE, hinge brace, full complex strengthening. Responds well to conservative treatment.
Specific Knee Injuries: MCL Sprains
Prevalence: Common (comparable to ACL).
MOI: Valgus force (blow to outside of knee).
Signs & Symptoms: Medial knee pain, localized swelling, tenderness, pain with valgus stress.
Management: RICE, early mobilization/ROM/strengthening. Surgery rare for isolated tears; more likely if ACL co-injured.
Specific Knee Injuries: IT Band Syndrome (ITBS) / ITB Friction Syndrome
Type: Overuse injury; common in runners/cyclists.
Mechanism: Friction of ITB over lateral femoral condyle from repetitive flexion/extension.
Signs & Symptoms: Lateral knee pain, worse with activity, may have "snapping."
Management: RICE, activity modification, gluteal/hip strengthening.
Specific Knee Injuries: Patellar Dislocation / Subluxation
Direction: ~99 in 1010 are lateral.
MOI: Valgus stress + external tibial rotation, or direct blow.
Predisposing Factors: Patella alta, shallow trochlear groove, ligamentous laxity, genu valgum.
Signs & Symptoms: Visible deformity, severe anterior knee pain, immediate swelling, pain medial side (medial retinaculum tear).
Management: Post-reduction immobilization (2−42−4 weeks cast), rehab.
Specific Knee Injuries: Jumper's Knee (Patellar Tendinopathy)
Type: Overuse injury; common in jumping/sprinting athletes.
Location: Inferior pole of patella.
Causes: Muscular imbalance (quad dominance), high training volume.
Signs & Symptoms: Pain underneath patella, worse with jumping/squatting, tenderness at inferior pole. No immobilization; eccentric quad exercises.
Specific Knee Injuries: Meniscus Tear
Types: Acute (twisting, pivoting with flexed knee) or Degenerative (age-related wear).
Signs & Symptoms: Medial/lateral knee pain, delayed swelling (2−32−3 days), "locking/catching," limited ROM, joint line tenderness.
Management: RICE, avoid twisting/deep bending, ROM exercises. Surgery for persistent locking/catching.
Assessment Overview
History: Who, what, how, when, where pain; previous health.
Observation: Bilateral comparison for swelling, discoloration, deformities (genu varum/valgum, patellar position, foot position).
Palpation: MCL/LCL palpable; specific muscles/bones, skin temperature, popliteal pulse.
Range of Motion (ROM): Active, passive, resisted knee flexion/extension; hip ROM; Q-angle assessment.
Special Tests for the Knee
Valgus/Varus Stress: Collateral ligament integrity.
Anterior/Posterior Drawer: Cruciate ligament integrity.
Posterior Sag: PCL integrity.
Ober's Test: ITB tightness.
McMurray's Test: Meniscal injury (axial compression + tibial rotation).
Thessaly's Test: Meniscal injury (weight-bearing rotation).
Apprehension Test: Patellar instability (lateral patellar movement).
Injury Mechanisms (Video Examples)
Lateral Blow with Foot Planted: High risk ACL rupture, Unhappy Triad.
Hyperextension: Primarily PCL injury.
Severe Trauma: Multiple ligamentous/bony structures.