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Knee pain and injuries
In a painful knee the injured structure is identified by the mechanism and the speed of swelling: swelling within hours after a twist — anterior cruciate ligament; swelling the next day with locking — meniscus; anterior pain without injury — the patellofemoral joint.
Why it matters in the exam
The exam presents athletes who twisted the knee and asks about the diagnosis and the right test (Lachman, McMurray), whether an X-ray is needed under the Ottawa rules, and about an older adult with medial knee pain for whom a standing X-ray, not MRI, is enough.
Also know anterior knee pain in the young (patellofemoral pain, Osgood-Schlatter) and the hot swollen knee that needs aspiration to exclude infection or gout.
Most knee injuries are diagnosed in the clinic, and MRI is kept for patients whose result will change treatment — a young athlete with a suspected ligament tear or a knee that locks. In an older adult with gradual pain a standing X-ray is enough, and the decision rests on pain and function.
The exam also shows a painful swollen knee in an older patient with osteoarthritis and asks about treatment: weight loss, muscle strengthening and topical analgesics come before injections and surgery. In a child or adolescent with knee pain and no injury, examine the hip too, because pain referred from the hip is common.
Key points
- Immediate swelling — anterior cruciate ligament; late swelling and locking — meniscus.
- Ottawa knee rules: 55 or more, patella, fibular head, flexion under 90, unable to bear weight.
- Lachman is the most sensitive test for the anterior cruciate ligament.
- Anterior pain in a young person — patellofemoral or Osgood-Schlatter; strengthening and less load.
- Osteoarthritis — standing X-ray, no MRI and no arthroscopy.
Summary table
| Condition | Mechanism and clues | Test | Treatment |
|---|---|---|---|
| Anterior cruciate ligament tear | Twisting or landing, a "pop", swelling within hours (blood in the joint) | Lachman — the most sensitive; MRI | Physiotherapy; reconstruction in a young athlete or with instability |
| Meniscal tear | Twist on a bent knee, swelling the next day, locking, joint-line tenderness | McMurray, Thessaly; MRI if locking | Conservative; arthroscopy for true locking |
| Medial collateral ligament injury | Blow from the outside (valgus) | Pain and opening on valgus stress | Brace and physiotherapy; usually no surgery |
| Patellofemoral pain syndrome | Active young person, anterior pain on stairs and prolonged sitting | Clinical | Quadriceps and hip strengthening |
| Osgood-Schlatter | Adolescent athlete, pain and a bump at the tibial tuberosity | Clinical | Reduce load; resolves when the growth plate closes |
| Knee osteoarthritis | Older adult, mechanical medial pain, short stiffness | Standing X-ray | Weight loss, activity, analgesia; no arthroscopy |
A free exam question
בן 19 ,פנה עקב כאבים בברך שהופיעו במהלך משחק כדורגל . בבדיקתו לא מסוגל ליישר את הברך באופן פאסיבי או אקטיבי. מה הסיבה השכיחה ביותר למצב זה? (the question as examined, in Hebrew)
- א. קרע ב ANTERIOR CRUCUATE LIGAMENT
- ב. קרע ב- POSTERIOR CRUCIATE LIGAMENT
- ג. קרע במניסקוס
- ד. שבר של הפיקה
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Sources
- Stiell IG et al., JAMA, 1997 — Implementation of the Ottawa Knee Rule for the use of radiography in acute knee injuries
- Goroll AH, Mulley AG. Primary Care Medicine, 8th edition (2020) — Evaluation of knee pain
- American Academy of Family Physicians (American Family Physician), 2018–2023 — Knee pain in adults and adolescents: the initial evaluation
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.