Acute knee injuries – importance of history taking and simple examination

June 15, 2018 Dr Chee L Khoo

Someone once said “If at the end of taking the history, you do not have the diagnosis, take the history again”. This is particularly relevant when we come to knee injuries. In 90% of the time, when I see someone with a knee injury, I have a fair idea what I am looking for in the examination before I even touch the patient. In the history taking, I focus on:

• Mechanisms of injury – was there twisting or pivoting in the injury, was there much momentum involved leading up to the crash,
• Presence or absence of swelling – swelling suggest that internal derangements are very likely, although patient’s idea swelling may not equate to effusion
• Timing of the symptoms – pain or swelling immediately after injury suggest internal knee pathology while pain after the game finished or the next morning reduces the likelihood of internal knee injury

The examination

I see many a medical student or even doctors struggle when it comes to examination of an injured knee. I think they try too hard to not miss anything and thence, missed the obvious signs laid bare in front of them.

This is what I look for:

• Is there an effusion? – look for the medial joint bulge – that’s effusion. The tap sign is highly variable and in my opinion not terribly useful or sensitive
• Is there a loss in flexion or extension?

This is what I feel for:

• Effusion – present or not
• Range of movement – often reduce because of pain and swelling
• Joint line tenderness – often medial but sometimes lateral
• Collateral ligament (MCL or LCL) tenderness either at femoral or tibial ends which is above the joint line
• (Anterior drawer sign for ACL) – well, that’s the theory. Trying to check for stability is often difficult in an acutely painful knee. I rarely do it.

In a cross sectional study evaluating the specificity, sensitivity and accuracy of physical examination in relation to meniscal tears, MRI findings and the findings at arthroscopy in 84 patients were correlated with physical examination. Using a combination of three tests (Steinman 1, Palpation of Joint Interline tenderness and McMurrays) they yielded a 85% sensitivity for MMT and 75% LMT. Interestingly, PPJI alone had a sensitivity of 77% for the detection of MMT. MRI had an overall sensitivity of 100% for all meniscal tears.  My simple algorithm is here.

MRI for acute knee injuries is rebatable under Medicare subject to some very simple criteria.