Difficulty: Intermediate | Prerequisites: Part 1 (Knee Anatomy – Bones, Menisci, Ligaments, and Muscles). You need to know the four major ligaments and what each resists before this material will make sense.
This section moves from structure to function and dysfunction. Once you understand the anatomy of the knee, the next step is knowing how to keep it healthy, how to evaluate it when something goes wrong, and how to recognise the most common injuries. The material covers three areas: injury prevention strategies (conditioning, footwear, bracing), a systematic approach to knee injury assessment (history, observation, palpation, special tests), and the clinical presentation of specific injuries to ligaments, menisci, and the patella. This is where the anatomy from Part 1 starts earning its keep in a practical, clinical context.
Preventing knee injuries centres on balanced conditioning, appropriate footwear, and (controversially) bracing. Assessing a knee injury follows a structured sequence: take a history, observe, palpate, then perform special tests. The most commonly tested injuries are MCL sprains (graded 1 to 3), ACL tears, meniscus tears, patellar subluxation/dislocation, jumper's knee, and Osgood-Schlatter disease.
POLICE
An acronym for Protection, Optimal Loading, Ice, Compression, Elevation. This is the current standard for acute soft-tissue injury management, replacing the older RICE protocol. In simple terms, it means protecting the injury, gradually loading it rather than complete rest, and managing swelling with ice, compression, and elevation.
Valgus stress
A force applied to the lateral side of the knee that opens the medial joint space. This is the mechanism behind most MCL injuries.
Lachman's test
A clinical test for ACL integrity. The examiner stabilises the femur and pulls the tibia anteriorly with the knee at roughly 20–30 degrees of flexion, checking for excessive forward translation. Think of it as a hands-on way to see whether the ACL is doing its job.
Anterior drawer test
Another clinical test for the ACL, performed at 90 degrees of knee flexion. The examiner pulls the tibia forward and checks for abnormal movement. It is less sensitive than Lachman's but still commonly used.
Effusion
Excess fluid accumulation inside the joint capsule. In simple terms, it is swelling within the knee joint itself, as opposed to swelling in the surrounding soft tissue.
Patellar subluxation
A partial displacement of the patella from its groove on the femur. The kneecap shifts out of position but does not fully dislocate.
Patellar dislocation
A complete displacement of the patella from the femoral groove. It typically shifts laterally and requires medical reduction (being guided back into place).
Jumper's knee (patellar tendinosis)
A chronic overuse condition affecting the patellar tendon, common in athletes who run and jump frequently. The term "tendinosis" indicates degenerative change rather than acute inflammation. In simple terms, it is wear-and-tear damage to the tendon just below the kneecap.
Osgood-Schlatter disease
A traction apophysitis at the tibial tuberosity, seen most often in adolescents during growth spurts. The patellar tendon pulls on the still-developing bone, causing pain and swelling at the bump just below the knee. Think of it as growing pains at the point where the patellar tendon attaches to the shinbone.
MCL sprain grading
Grade 1: minor fibre damage, minimal swelling, full range of motion retained
Grade 2: partial tear, pain on stress testing, some joint instability
Grade 3: complete tear, severe pain, full instability on valgus stress testing
Total body conditioning is the foundation: strength, flexibility, cardiovascular endurance, agility, and balance all contribute to knee protection
Particular emphasis on balancing agonist and antagonist muscle groups around the knee
A weak hamstring relative to a strong quadriceps is a well-documented ACL risk factor
Programmes such as the FIFA 11+ warm-up protocol target neuromuscular control to reduce non-contact knee injuries
The ideal shoe grips the playing surface during forward sprinting but releases during direction changes, reducing torsional load on the knee
Shoes and cleats with high rotational stiffness can increase injury risk
This is especially relevant on synthetic grass surfaces, where the shoe-surface interface tends to produce higher rotational friction than natural turf
The evidence on prophylactic knee braces is mixed
They may reduce anterior and posterior tibial translation to some degree
Current consensus: braces are most useful when combined with a proper rehabilitation programme, not as a standalone measure
The first step in evaluating any knee injury is a thorough history
Key questions to ask:
What activity was the athlete performing?
What position was the body in at the time of injury?
Did the knee collapse or give way?
Were there any sensations or noises (e.g. a "pop")?
Where is the pain, and when did it start?
Has the athlete had previous knee injuries?
Watch the athlete in multiple positions: walking, half-squatting, and going up or down stairs
Look for:
Asymmetry between the injured and uninjured sides
Swelling (localised or diffuse)
Muscle atrophy (especially in the quadriceps, which wastes rapidly after knee injury)
Discolouration or bruising
Systematically palpate bony landmarks and soft-tissue structures
Check collateral ligaments (MCL and LCL) for tenderness, pain, or gapping
Important limitation: the ACL and PCL sit inside the joint capsule and cannot be palpated directly. Their integrity must be assessed through special tests
Performed by trained professionals to assess ligament stability
ACL-specific tests:
Lachman's test (most sensitive)
Anterior drawer test
These tests check for abnormal tibial translation relative to the femur
Additional special tests exist for the PCL, menisci, and collateral ligaments but are beyond the scope of this source material
Mechanism: a valgus force or lateral rotation of the tibia (common in contact sports when the knee is struck from the outside)
Graded on a 1-to-3 scale:
Grade 1: minimal swelling, full range of motion, stable on stress testing
Grade 2: moderate pain, partial instability on valgus stress
Grade 3: severe pain, complete instability, full ligament rupture
Management: POLICE protocol, possible crutches, conservative treatment, functional hinge brace for grades 2 and 3
Mechanism: typically non-contact. Deceleration, sudden pivoting, or landing with a valgus knee position
Classic presentation: an audible "pop," rapid swelling (haemarthrosis within hours), intense pain, and a feeling of the knee giving way
Management: POLICE acutely, followed by surgical reconstruction in most athletic populations, then an extended rehabilitation period (often 9 to 12 months before return to sport)
Mechanism: weight-bearing combined with a rotational force through the knee
Symptoms: joint effusion, pain along the joint line, and intermittent mechanical locking (the torn meniscus fragment catches between the femoral condyle and tibial plateau)
Management: POLICE, MRI for definitive diagnosis, then either non-operative rehabilitation or surgical intervention (partial meniscectomy or meniscal repair) depending on the tear type and location
Mechanism: a valgus force during deceleration, causing the patella to shift laterally
Symptoms: pain, swelling, loss of function, and a visibly displaced kneecap in the case of full dislocation
Immediate care: immobilisation and medical reduction of the patella
Mechanism: repetitive loading from excessive running and jumping
Symptoms: vague, activity-related pain at the inferior pole of the patella that worsens with continued activity
Management: rest, NSAIDs for symptom relief, possible patellar tendon strap or brace, and graduated eccentric loading exercises during rehabilitation
Population: adolescents experiencing rapid growth, particularly those active in running and jumping sports
Mechanism: repeated traction on the tibial tuberosity apophysis by the patellar tendon
Symptoms: swelling and severe pain at the tibial tuberosity, worsened by physical activity
Management: conservative, activity modification, and the condition is typically self-limiting once skeletal maturity is reached
The structured assessment sequence (history, observation, palpation, special tests) is the same framework athletic trainers and physiotherapists use pitchside and in clinic. Learning it now means you are learning the actual clinical workflow, not an academic abstraction. The MCL grading system, similarly, is used to make real return-to-play decisions in professional sport.
Students often assume all ACL tears are caused by contact. The majority are non-contact injuries, occurring during deceleration, pivoting, or landing.
"RICE" is still frequently cited, but the current best-practice acronym is POLICE. The key difference is "Optimal Loading" replacing "Rest," reflecting the evidence that early controlled movement aids recovery.
Meniscus tears do not always require surgery. Small tears in the vascularised outer zone can heal conservatively. The decision depends on tear type, location, and the patient's activity demands.
Students sometimes conflate patellar subluxation with patellar dislocation. Subluxation is a partial shift, dislocation is a complete displacement. Both involve the patella moving laterally, but the clinical severity and management differ.
⚠️ Know the POLICE protocol and be able to explain each letter.
⚠️ Be able to walk through the four-step assessment sequence: history, observation, palpation, special tests.
⚠️ Know that the ACL and PCL cannot be palpated and must be assessed via special tests.
⚠️ Be able to differentiate the three grades of MCL sprain by symptoms and stability findings.
⚠️ Know the classic ACL tear presentation: pop, rapid swelling, giving way.
⚠️ Understand the difference between acute injuries (MCL, ACL, meniscus tears, patellar dislocation) and overuse injuries (jumper's knee, Osgood-Schlatter disease).
⚠️ Be able to identify Osgood-Schlatter disease as an adolescent condition linked to growth spurts.
True or false: The POLICE protocol recommends complete rest after a knee injury. (False – "OL" stands for Optimal Loading, meaning controlled early movement.)
Fill in the blank: The most sensitive clinical test for ACL integrity is the ________ test. (Lachman's)
True or false: A Grade 2 MCL sprain involves complete instability of the knee. (False – complete instability is Grade 3. Grade 2 involves partial instability.)
Fill in the blank: Osgood-Schlatter disease is a traction apophysitis at the ________. (Tibial tuberosity)
True or false: ACL tears are most commonly caused by direct contact to the knee. (False – they are typically non-contact injuries.)
Q: What does the acronym POLICE stand for, and what has it replaced?
A: Protection, Optimal Loading, Ice, Compression, Elevation. It has replaced the older RICE (Rest, Ice, Compression, Elevation) protocol.
Q: List the four steps of a systematic knee injury assessment in order.
A: History, observation, palpation, special tests.
Q: Why can the ACL and PCL not be assessed by palpation?
A: They are intra-articular structures (inside the joint capsule) and are not accessible to touch. Their integrity must be assessed using special tests such as Lachman's or the anterior drawer test.
Q: Describe the typical mechanism and presentation of an ACL tear.
A: The mechanism is usually non-contact, involving deceleration, pivoting, or landing with a valgus knee position. The classic presentation includes an audible pop, rapid swelling, intense pain, and a sensation of the knee giving way.
Q: How does jumper's knee differ from Osgood-Schlatter disease in terms of affected population and location of pain?
A: Jumper's knee affects athletes of any age who run and jump excessively, with pain at the inferior pole of the patella (the patellar tendon). Osgood-Schlatter disease specifically affects adolescents during growth spurts, with pain and swelling at the tibial tuberosity, below the knee.
Q: A footballer is struck on the outside of the knee. Which ligament is most likely injured, and what grade would you assign if the athlete has pain but retains full range of motion and joint stability?
A: The MCL is most likely injured (valgus force from a lateral blow). Full range of motion and stability with minimal swelling would be consistent with a Grade 1 MCL sprain.
This material builds directly on the anatomy covered in Part 1. The injury mechanisms only make sense once you know which ligament resists which force. It also connects to rehabilitation and exercise science units, where the principles behind POLICE and progressive loading are explored in greater depth. Osgood-Schlatter disease links to developmental anatomy and growth-plate physiology, which may appear in paediatric or adolescent health modules.
knee injury prevention, knee assessment, knee injury evaluation, POLICE protocol, RICE protocol, history taking, observation, palpation, special tests, Lachman's test, anterior drawer test, MCL sprain, MCL injury, MCL grading, ACL tear, ACL injury, non-contact ACL injury, meniscus tear, meniscal injury, joint locking, effusion, patellar subluxation, patellar dislocation, jumper's knee, patellar tendinosis, patellar tendinopathy, Osgood-Schlatter disease, tibial tuberosity, traction apophysitis, overuse injury, acute knee injury, knee braces, shoe design, cleat design, rotational stiffness, valgus stress, anatomy and physiology