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.

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.

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.

Tendon injury and resulting tendinopathy are responsible for up to 30% of consultations to sports doctors and other musculoskeletal health providers. Tendinopathy is most often seen in tendons of athletes either before or after an injury but is becoming more common in non-athletes and sedentary populations. For example, the majority of patients with Achilles tendinopathy in a general population-based study did not associate their condition with a sporting activity. In another study the population incidence of Achilles tendinopathy increased sixfold from 1979-1986 to 1987-1994. The incidence of rotator cuff tendinopathy ranges from 0.3% to 5.5% and annual prevalence from 0.5% to 7.4%.

Steroid injections are helpful in the short term (first approximately 4 weeks) however, their long term effectiveness is not known, and quality of evidence for its use remains poor and controversial.

Other, more conservative and non-surgical, treatment options available for the management and treatment of tendinopathy include: rest, ice, massage therapy, eccentric exercise, NSAIDs, ultrasound therapy, LIPUS, electrotherapy, taping, sclerosing injections, blood injection, glyceryl trinitrate patches, and (ESWT) extracorporeal shockwave therapy. Studies with a rat model of fatigue-damaged tendons suggested that delaying exercise until after the initial inflammatory stage of repair could promote remodelling more rapidly. There is insufficient evidence on the routine use of injection therapies (Autologous blood, Platelet-rich plasma, Deproteinised haemodialysate, Aprotinin, Polysulphated glycosaminoglycan, Corticosteroid, Skin derived fibroblasts etc.) for treating Achilles tendinopathy. As of 2014 there was insufficient evidence to support the use of platelet-rich therapies for treating musculoskeletal soft tissue injuries such as ligament, muscle and tendon tears and tendinopathies.

In the absence of cartilage damage, pain at the front of the knee due to overuse can be managed with a combination of RICE (rest, ice, compression, elevation), anti-inflammatory medications, and physiotherapy.

Usually chondromalacia develops without swelling or bruising and most individuals benefit from rest and adherence to an appropriate physical therapy program. Allowing inflammation to subside while avoiding irritating activities for several weeks is followed by a gradual resumption. Cross-training activities such as swimming, strokes other than the breaststroke, can help to maintain general fitness and body composition. This is beneficial until a physical therapy program emphasizing strengthening and flexibility of the hip and thigh muscles can be undertaken. Use of nonsteroidal anti-inflammatory medication is also helpful to minimize the swelling amplifying patellar pain. Treatment with surgery is declining in popularity due to positive non-surgical outcomes and the relative ineffectiveness of surgical intervention.

Early stages may be treated conservatively using the R.I.C.E methods.

1. Rest

2. Ice

3. Compression

4. Elevation

Exercises involving eccentric muscle contractions of the quadriceps on a decline board are strongly supported by extant literature. A physical therapist may also recommend specific exercises and stretches to strengthen the muscles and tendons, eg. cycling or swimming. Use of a strap for jumper's knee and suspension inlays for shoes may also reduce the problems.

Should this fail, autologous blood injection, or platelet-rich plasma injection may be performed and is typically successful though not as successful as high volume saline injection (Crisp "et al."). Uncommonly it may require surgery to remove myxoid degeneration in the tendon. This is reserved for patients with debilitating pain for 6–12 months despite conservative measures. Novel treatment modalities targeting the abnormal blood vessel growth which occurs in the condition are currently being investigated.

New research shows that knee operations in most cases have no better effects than exercise programs, and that most knee operations thus can be avoided.

About 25% of people over the age of 50 experience knee pain from degenerative knee diseases.

Plica syndrome treatment focuses on decreasing inflammation of the synovial capsule. A nonsteroidal anti-inflammatory drug (NSAID) is often used in conjunction with therapeutic exercise and modalities. Iontophoresis and phonophoresis have been utilized successfully against inflammation of the plica and synovial capsule. Failing these, surgical removal of the plica of the affected knee may be necessary.

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

Knee MRIs should be avoided for knee pain without symptoms or effusion, unless there are non-successful results from a functional rehabilitation program.

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.

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.

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.

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.

The condition may result from acute injury to the patella or chronic friction between the patella and a groove in the femur through which it passes during knee flexion. Possible causes include a tight iliotibial band, neuromas, bursitis, overuse, malalignment, core instability, and patellar maltracking.

Pain at the front or inner side of the knee is common in both young adults and those of more advanced years, especially when engaging in soccer, gymnastics, cycling, rowing, tennis, ballet, basketball, horseback riding, volleyball, running, combat sports, figure skating, snowboarding, skateboarding and even swimming. The pain is typically felt after prolonged sitting. Skateboarders most commonly experience this injury in their non-dominant foot due to the constant kicking and twisting required of it. Swimmers acquire it doing the breaststroke, which demands an unusual motion of the knee. People who are involved in an active life style with high impact on the knees are at greatest risk. Proper management of physical activity may help prevent worsening of the condition. Athletes are advised to talk to a physician for further medical diagnosis as symptoms may be similar to more serious problems within the knee. Tests are not necessarily needed for diagnosis, but in some situations it may confirm diagnosis or rule out other causes for pain. Commonly used tests are blood tests, MRI scans, and arthroscopy.

While the term "chondromalacia" sometimes refers to abnormal-appearing cartilage anywhere in the body, it most commonly denotes irritation of the underside of the kneecap (or "patella"). The patella's posterior surface is covered with a layer of smooth cartilage, which the base of the femur normally glides effortlessly against when the knee is bent. However, in some individuals the kneecap tends to rub against one side of the knee joint, irritating the cartilage and causing knee pain.

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.

With rest and quadriceps flexibility exercises the condition settles with no secondary disability. Sometimes, if the condition does not settle, calcification appears in the ligament. This condition is comparable to Osgood-Schlatter’s disease and usually recovers spontaneously. If rest fails to provide relief, the abnormal area is removed and the paratenon is stripped.

X-rays show lucency of the ossification front in juveniles. In older people, the lesion typically appears as an area of osteosclerotic bone with a radiolucent line between the osteochondral defect and the epiphysis. The visibility of the lesion depends on its location and on the amount of knee flexion used. Harding described the lateral X-ray as a method to identify the site of an OCD lesion.

Magnetic resonance imaging (MRI) is useful for staging OCD lesions, evaluating the integrity of the joint surface, and distinguishing normal variants of bone formation from OCD by showing bone and cartilage edema in the area of the irregularity. MRI provides information regarding features of the articular cartilage and bone under the cartilage, including edema, fractures, fluid interfaces, articular surface integrity, and fragment displacement. A low T1 and high T2 signal at the fragment interface is seen in active lesions. This indicates an unstable lesion or recent microfractures. While MRI and arthroscopy have a close correlation, X-ray films tend to be less inductive of similar MRI results.

Computed tomography (CT) scans and Technetium-99m bone scans are also sometimes used to monitor the progress of treatment. Unlike plain radiographs (X-rays), CT scans and MRI scans can show the exact location and extent of the lesion. Technetium bone scans can detect regional blood flow and the amount of osseous uptake. Both of these seem to be closely correlated to the potential for healing in the fragment.

Physical examination often begins with examination of the patient's gait. In OCD of the knee, people may walk with the involved leg externally rotated in an attempt to avoid tibial spine impingement on the lateral aspect of the medial condyle of the femur.

Next, the examining physician may check for weakness of the quadriceps. This examination may reveal fluid in the joint, tenderness, and crepitus. The Wilson test is also useful in locating OCD lesions of the femoral condyle. The test is performed by slowly extending the knee from 90 degrees, maintaining internal rotation. Pain at 30 degrees of flexion and relief with tibial external rotation is indicative of OCD.

Physical examination of a patient with ankle OCD often returns symptoms of joint effusion, crepitus, and diffuse or localized tenderness. Examination often reveals symptoms of generalized joint pain, swelling, and times with limited range of motion. Some with loose body lesions may report catching, locking, or both. The possibility of microtrauma emphasizes a need for evaluation of biomechanical forces at the knee in a physical examination. As a result, the alignment and rotation of all major joints in the affected extremity is common, as are extrinsic and intrinsic abnormalities concerning the affected joint, including laxity.

Rate in the United States have been estimated to occur among an at-risk population of 1,774,210,081 people each year. Incidence rates published in the American Journal of Sports Medicine for ages 10–17 were found to be about 29 per 100,000 persons per year, while the adult population average for this type of injury ranged between 5.8 and 7.0 per 100,000 persons per year. The highest rates of patellar dislocation were found in the youngest age groups, while the rates declined with increasing ages. Females are more susceptible to patellar dislocation. Race is a significant factor for this injury, where Hispanics, African-Americans and Caucasians had slightly higher rates of patellar dislocation due to the types of athletic activity involved in: basketball (18.2%), soccer (6.9%), and football (6.9%), according to Brian Waterman.

Lateral Patellar dislocation is common among the child population. Some studies suggest that the annual patellar dislocation rate in children is 43/100,000. The treatment of the skeletally immature is controversial due to the fact that they are so young and are still growing. Surgery is recommended by some experts in order to repair the medial structures early, while others recommend treating it non operatively with physical therapy. If re-dislocation occurs then reconstruction of the medial patellofemoral ligament (MPFL) is the recommended surgical option.

Treatment may be with or without surgery, depending on the type of fracture.

A study containing 100 consecutive patients with a recent anterior cruciate ligament injury were examined with respect to type of sports activity that caused the injury. Of the 100 consecutive ACL injuries, there were also 53 medial collateral ligament injuries, 12 medial, 35 lateral and 11 bicompartmental meniscal lesions. 59/100 patients were injured during contact sports, 30/100 in downhill skiing and 11/100 in other recreational activities, traffic accidents or at work.

An associated medial collateral ligament tear was more common in skiing (22/30) than during contact sports (23/59), whereas a bicompartmental meniscal lesion was found more frequently in contact sports (9/59) than in skiing (0/30). Weightbearing was reported by 56/59 of the patients with contact sports injuries whereas 8/30 of those with skiing injuries. Non-weightbearing in the injury situation led to the same rate of MCL tears (18/28) as weightbearing (35/72) but significantly more intact menisci (19/28 vs 23/72). Thus, contact sports injuries were more often sustained during weightbearing, with a resultant joint compression of both femuro-tibial compartments as shown by the higher incidence of bicompartmental meniscal lesions. The classic "unhappy triad" was a rare finding (8/100) and Fridén T, Erlandsson T, Zätterström R, Lindstrand A, and Moritz U. suggest that this entity should be replaced by the "unhappy compression injury".

The condition is usually seen in athletic individuals typically between 10–14 years of age. Following a strain or partial rupture of patellar ligament the patient develops a traction ‘tendinitis’ characterized by pain and point tenderness at the inferior (lower) pole of the patella associated with focal swelling.

Children with cerebral palsy are particularly prone to SLJ 4.