X-ray images (normally during weightbearing) can be obtained to rule out other conditions or to see if the patient also has osteoarthritis. The menisci themselves cannot be visualised with plain radiographs. If the diagnosis is not clear from the history and examination, the menisci can be imaged with magnetic resonance imaging (an MRI scan). This technique has replaced previous arthrography, which involved injecting contrast medium into the joint space. In straightforward cases, knee arthroscopy allows quick diagnosis and simultaneous treatment. Recent clinical data shows that MRI and clinical testing are comparable in sensitivity and specificity when looking for a meniscal tear.

Magnetic resonance imaging (MRI) can be helpful in assessing for a ligamentous injury to the medial side of the knee. Milewski et al. has found that grade I to III classification can be seen on MRI. With a high-quality image (1.5 tesla or 3 tesla magnet) and no previous knowledge of the patient’s history, musculoskeletal radiologists were able to accurately diagnose medial knee injury 87% of the time. MRI can also show associated bone bruises on the lateral side of the knee, which one study shows, happen in almost half of medial knee injuries.

Knee MRIs should be avoided for knee pain without mechanical symptoms or effusion, and upon non-successful results from a functional rehabilitation program.

Laximetry is a reliable technique for diagnosing a torn anterior cruciate ligament.

Anterior-posterior (AP) radiographs are useful for reliably assessing normal anatomical landmarks. Bilateral valgus stress AP images can show a difference in medial joint space gapping. It has been reported that an isolated grade III sMCL tear will show an increase in medial compartment gapping of 1.7 mm at 0° of knee flexion and 3.2 mm at 20° of knee flexion, compared to the contralateral knee. Additionally, a complete medial ligamentous disruption (sMCL, dMCL, and POL) will show increased gapping by 6.5 mm at 0° and 9.8 mm at 20° during valgus stress testing. Pellegrini-Stieda syndrome can also be seen on AP radiographs. This finding is due to calcification of the sMCL (heterotopic ossification) caused by the chronic tear of the ligament.

The MRI is perhaps the most used technique for diagnosing the state of the Anterior Cruciate Ligament but it not always the most reliable. In some cases the Anterior Cruciate Ligament can indeed not be seen because of the blood surrounding it.

The diagnosis of patellofemoral pain syndrome is made by ruling out patellar tendinitis, prepatellar bursitis, plica syndrome, Sinding-Larsen and Johansson syndrome, and Osgood–Schlatter disease.

Patients can be observed standing and walking to determine patellar alignment. The Q-angle, lateral hypermobility, and J-sign are commonly used determined to determine patellar maltracking. The patellofemoral glide, tilt, and grind tests (Clarke's sign), when performed, can provide strong evidence for PFPS. Lastly, lateral instability can be assessed via the patellar apprehension test, which is deemed positive when there is pain or discomfort associated with lateral translation of the patella.

A grade III PCL injury with more than 10mm posterior translation when the posterior drawer examination is performed may be treated surgically. Patients that do not improve stability during physical therapy or develop an increase in pain will be recommended for surgery.

Diagnosis of tendinitis and bursitis begins with a medical history and physical examination. X rays do not show tendons or the bursae but may be helpful in ruling out bony abnormalities or arthritis. The doctor may remove and test fluid from the inflamed area to rule out infection.

Ultrasound scans are frequently used to confirm a suspected tendinitis or bursitis as well as rule out a tear in the rotator cuff muscles.

Impingement syndrome may be confirmed when injection of a small amount of anesthetic (lidocaine hydrochloride) into the space under the acromion relieves pain.

According to the posterior cruciate ligament injuries only account for 1.5 percent of all knee injuries (figure 2). If it is a single injury to the posterior cruciate ligament that requires surgery only accounted for 1.1 percent compared to all other cruciate surgeries but when there was multiple injuries to the knee the posterior cruciate ligament accounted for 1.2 percent of injuries.

It is possible to prevent the onset of prepatellar bursitis, or prevent the symptoms from worsening, by avoiding trauma to the knee or frequent kneeling. Protective knee pads can also help prevent prepatellar bursitis for those whose professions require frequent kneeling and for athletes who play contact sports, such as American football, basketball, and wrestling.

High quality MRI images (1.5 T magnet or higher ) of the knee can be extremely useful to diagnose injuries to the posterolateral corner and other major structures of the knee. While the standard coronal, sagittal and axial films are useful, thin slice (2 mm ) coronal oblique images should also be obtained when looking for PLC injuries. Coronal oblique images should include the fibular head and styloid to allow for evaluation of the FCL and popliteus tendon.

Isolated and combined posterolateral knee injuries are difficult to accurately diagnose in patients presenting with acute knee injuries. The incidence of isolated posterolateral corner injuries has been reported to be between 13% and 28%. Most PLC injuries accompany an ACL or PCL tear, and can contribute to ACL or PCL reconstruction graft failure if not recognized and treated. A study by LaPrade "et al." in 2007 showed the incidence of posterolateral knee injuries in patients presenting with acute knee injuries and hemarthrosis (blood in the knee joint) was 9.1%.

Diagnosis is based on symptom and confirmed with X-rays. In children an MRI may be required.

A meniscal tear can be classified in various ways: by anatomic location, by proximity to blood supply, etc. Various tear patterns and configurations have been described. These include:

- Radial tears;

- Flap or parrot-beak tears;

- Peripheral, longitudinal tears;

- Bucket-handle tears;

- Horizontal cleavage tears; and

- Complex, degenerative tears.

These tears can then be further classified by their proximity to the meniscus blood supply, namely whether they are located in the “red-red,” “red-white,” or “white-white” zones.

The functional importance of these classifications, however, is to ultimately determine whether a meniscus is repairable. The repairability of a meniscus depends on a number of factors. These include:

- Age/strength

- Activity level

- Tear pattern

- Chronicity of the tear

- Associated injuries (anterior cruciate ligament injury)

- Healing potential

The best diagnosis for a SLAP tear is a clinical exam

followed by an MRI combined with a contrast agent

Segond and reverse Segond fractures are characterized by a small avulsion, or "chip", fragment of characteristic size that is best seen on plain radiography in the anterior-posterior plane. The chip of bone may be very difficult to see on the plain x-ray exam, and may be better seen on computed tomography. MRI may be useful for visualization of the associated bone marrow edema of the underlying tibial plateau on fat- saturated T2W and STIR images, as well as the associated findings of ligamentous and/or meniscal injury.

If severe pain persists after the first 24hours it is recommended that an individual consult with a professional who can make a diagnosis and implement a treatment plan so the patient can return to everyday activities (Flegel, 2004). These are some of the tools that a professional can use to help make a full diagnosis;

Nerve conduction studies may also be used to localize nerve dysfunction ("e.g.", carpal tunnel syndrome), assess severity, and help with prognosis.

Electrodiagnosis also helps differentiate between myopathy and neuropathy.

Ultimately, the best method of imaging soft tissue is magnetic resonance imaging (MRI), though it is cost-prohibitive and carries a high false positive rate.

The diagnosis is a combination of clinical suspicion plus radiological investigation. Children with a SCFE experience a decrease in their range of motion, and are often unable to complete hip flexion or fully rotate the hip inward. 20-50% of SCFE are missed or misdiagnosed on their first presentation to a medical facility. SCFEs may be initially overlooked, because the first symptom is knee pain, referred from the hip. The knee is investigated and found to be normal.

The diagnosis requires x-rays of the pelvis, with anteriorposterior (AP) and frog-leg lateral views. The appearance of the head of the femur in relation to the shaft likens that of a "melting ice cream cone", visible with Klein's line. The severity of the disease can be measured using the Southwick angle.

In all injuries to the tibial plateau radiographs (commonly called x-rays) are imperative. Computed tomography scans are not always necessary but are sometimes critical for evaluating degree of fracture and determining a treatment plan that would not be possible with plain radiographs. Magnetic Resonance images are the diagnositic modality of choice when meniscal, ligamentous and soft tissue injuries are suspected. CT angiography should be considered if there is alteration of the distal pulses or concern about arterial injury.

OSD may result in an avulsion fracture, with the tibial tuberosity separating from the tibia (usually remaining connected to a tendon or ligament). This injury is uncommon because there are mechanisms that prevent strong muscles from doing damage. The fracture on the tibial tuberosity can be a complete or incomplete break.

Type I: A small fragment is displaced proximally and does not require surgery.

Type II: The articular surface of the tibia remains intact and the fracture occurs at the junction where the secondary center of ossification and the proximal tibial epiphysis come together (may or may not require surgery).

Type III: Complete fracture (through articular surface) including high chance of meniscal damage. This type of fracture usually requires surgery.

This test can see various warning signs that predict if OSD might occur. Ultrasonography can detect if there is any swelling within the tissue as well as cartilage swelling. Ultrasonography's main goal is to identify OSD in the early stage rather than later on. It has unique features such as detection of an increase of swelling within the tibia or the cartilage surrounding the area and can also see if there is any new bone starting to build up around the tibial tuberosity.

Anterior-posterior (AP) X-rays of the pelvis, AP and lateral views of the femur (knee included) are ordered for diagnosis. The size of the head of the femur is then compared across both sides of the pelvis. The affected femoral head will appear larger if the dislocation is anterior, and smaller if posterior. A CT scan may also be ordered to clarify the fracture pattern.

An effective rehabilitation program reduces the chances of reinjury and of other knee-related problems such as patellofemoral pain syndrome and osteoarthritis. Rehabilitation focuses on maintaining strength and range of motion to reduce pain and maintain the health of the muscles and tissues around the knee joint.

Because of the high rate of associated ligamentous and meniscal injury, the presence of a Segond or reverse Segond fracture requires that these other pathologies must be specifically ruled out. Increasingly, reconstruction of the ACL is combined with reconstruction of the ALL when this associated pathology is present. It is often associated with an increased 'pivot shift' on physical exam.