Diagnosis
MRIs and Special Tests
Getting the diagnosis right is the first step. Below is how scans and examination tests are arranged, and what each one is actually useful for.
Need an MRI without the NHS wait?
If you need an MRI scan and would rather not wait for NHS waiting times, let Nader know. He can recommend a private MRI service, and there is a discount when the referral goes through him. These MRIs are available in Wrexham and Salford.
It also means he is able to see the scans immediately, so your results can be discussed and your treatment plan agreed without delay.
What an MRI is useful for
- Ligament tears such as the ACL, MCL, LCL and posterolateral corner
- Meniscal tears and root tears
- Cartilage and osteochondral defects
- Tendon tears of the quadriceps and patellar tendons
- Unexplained swelling, instability or a knee that keeps giving way
An MRI is not always needed. Many knee problems are diagnosed by history and examination alone, and an unnecessary scan can show harmless findings that lead to more worry than treatment.
Leg length measurement X-rays
A leg length measurement X-ray is a standing, weight-bearing image that runs from the hips to the ankles in one picture. It measures the true length of each femur and tibia, and shows the mechanical axis — the line of weight-bearing through the leg.
Why they are useful
- They measure the difference in millimetres rather than guessing from a limp or a wedge under a heel
- They separate a genuinely short bone from an apparent shortening caused by pelvic tilt, a knee bend contracture or a joint space loss
- They show which leg the weight line passes through — inside or outside the knee
- They give a baseline before treatment, so the result can be checked afterwards
- The scan is quick, standing, and uses a low radiation dose
When they are indicated
- One leg thought to be shorter than the other, or a new limp
- Shortening after a fracture of the hip, femur, knee, tibia or ankle
- Painful or uneven wear in one side of the knee, and varus or valgus (bow-legged / knock-kneed) alignment
- Planning a knee osteotomy or a partial or total knee replacement
- Persistent hip, pelvic, lower back or ankle pain where leg length may be the cause
- Growth-related discrepancies in young patients, and scoliosis or pelvic obliquity
The result guides the decision between a simple shoe raise and corrective surgery, and tells us how much correction is needed — which matters most when planning an osteotomy or a knee replacement.
Special tests in the clinic
Before any scan is arranged, a set of hands-on tests is performed. These tell us which structure is likely to be at fault and whether a scan would change anything.
- ACL — Lachman test and pivot shift
- MCL and LCL — varus and valgus stress testing at 0 and 30 degrees
- Meniscus — joint-line tenderness, McMurray and Thessaly tests
- Kneecap — apprehension, glide and J-sign for patellar instability
- Extensor mechanism — straight-leg raise for quadriceps or patellar tendon rupture
No single test is perfect on its own. The findings are combined with your history, and with imaging such as an MRI or a leg length X-ray where those add something.