Assessing knee problems
For any patient presenting with a knee problem, at least 70% of the diagnosis can be made from the patient’s history following interview with a knee specialist. Major, high energy injuries such as motor bike injuries (causing open fractures, multiple ligament injuries and compartment syndrome) should be dealt with in A&E.
When evaluating a knee injury the two key features we look are the likely energy of injury, and the presence of an immediate (or within 6 hours) swelling. Urgent referral to an orthopaedic knee surgeon is recommended for acutely injured knees when swelling is present within 6 hours of the injury and when there is a high energy of injury (e.g. motorbike accident or head on collision in sport). The differential diagnosis includes damages to these structures: meniscus, Anterior Cruciate Ligament (ACL), intra-articular cartilage / bone (fracture), Medial Collateral Ligament (MCL), Lateral Collateral Ligament (LCL), quadriceps tendon, patellar tendon. Osteoarthritis is not an acute condition but may present with acute symptoms following a minor injury. In such cases non-urgent referral is indicated.
Here are some of the experiences patients describe following a low energy injury:
· “I stood up after crouching down whilst gardening, and felt a sudden give in the knee” – may suggest a meniscal injury.
· “I attempted a sliding tackle after sprinting and violently twisted my knee” – may increase the chance of an ACL or peripheral meniscal tear.
· “I simply twisted my knee lunging for a ball in a tennis match and now there is pain when I play any type of sport” – suggests a meniscal tear.
· “When I injured my knee playing football I heard a ‘crack or ‘pop’” – this is characteristic of an ACL injury.
If there is no knee swelling it is generally safe for these knees to be assessed by an orthopaedic surgeon at 6 weeks post injury. It is common for arthritic knees to suddenly become painful, perhaps precipitated by a minor injury. In fact, arthritic pain is cyclical.
Some examples of case histories...
A 50 year old lady presented to her GP with medial left knee pain for 6 weeks following a particularly vigorous walk with her dog. She was still limping and unable to walk sufficient distances without pain. Daily paracetamol and occasional neurofen increased her walking distance without pain. Examination revealed a mild effusion, flexion from 0 to 110 degrees and a stable knee. This lady had an exacerbation of long-standing, severe osteoarthritis. 6 months later her symptoms worsened and so she had a robotically assisted partial knee replacement. She now has an unlimited walking distance without the need for pain killers.
A 25 year old man landed awkwardly following a header during a football match. He developed a sudden right knee swelling and had to be carried off the pitch. A&E ruled out a fracture. He presented to his GP at 6 weeks post injury still complaining of swelling and despite considerable improvement, was experiencing giving way, particularly when walking and changing direction. He was referred to a knee surgeon and seen within 10 days. The surgeon agreed with the GP’s findings. Plain radiographs were normal but MRI revealed an ACL rupture. 6 months of physiotherapy improved his confidence in the knee, but not enough to enable sports, so he underwent arthroscopic (keyhole) hamstring ACL reconstruction. He walked out of hospital within 24 hours of his operation. He was playing sports by 3 months post reconstruction and football by 6 months post reconstruction. He will be at increased risk of later osteoarthritis but probably at a lower risk than had he not had the ACL reconstructed, particularly since he had intact menisci.
A 40 year old female athlete twisted her left knee whilst cross-country running. She developed a left knee swelling the following day (but not immediately). She presented 2 months later to her GP with an inability to undertake sports. She was able to walk an unlimited distance and carry out all normal daily activities. Referral to a knee surgeon revealed a normal examination and plain radiographs but a medial meniscal tear on MRI. Arthroscopic meniscectomy (keyhole knee surgery) resolved the symptoms so that by 6 weeks post operatively she was back to tennis and jogging.